Encoding functions

char

Returns the string with the length as the number of passed arguments and each byte has the value of corresponding argument. Accepts multiple arguments of numeric types. If the value of argument is out of range of UInt8 data type, it is converted to UInt8 with possible rounding and overflow.

Syntax

char(number_1, [number_2, ..., number_n]);

Arguments

• number_1, number_2, ..., number_n — Numerical arguments interpreted as integers. Types: Int, Float.

Returned value

• a string of given bytes. String.

Example

Query:

SELECT char(104.1, 101, 108.9, 108.9, 111) AS hello;

Result:

┌─hello─┐
│ hello │
└───────┘

You can construct a string of arbitrary encoding by passing the corresponding bytes. Here is example for UTF-8:

Query:

SELECT char(0xD0, 0xBF, 0xD1, 0x80, 0xD0, 0xB8, 0xD0, 0xB2, 0xD0, 0xB5, 0xD1, 0x82) AS hello;

Result:

┌─hello──┐
│ привет │
└────────┘

Query:

SELECT char(0xE4, 0xBD, 0xA0, 0xE5, 0xA5, 0xBD) AS hello;

Result:

┌─hello─┐
│ 你好  │
└───────┘

hex

Returns a string containing the argument's hexadecimal representation.

Alias: HEX.

Syntax

hex(arg)

The function is using uppercase letters A-F and not using any prefixes (like 0x) or suffixes (like h).

For integer arguments, it prints hex digits ("nibbles") from the most significant to least significant (big-endian or "human-readable" order). It starts with the most significant non-zero byte (leading zero bytes are omitted) but always prints both digits of every byte even if the leading digit is zero.

Values of type Date and DateTime are formatted as corresponding integers (the number of days since Epoch for Date and the value of Unix Timestamp for DateTime).

For String and FixedString, all bytes are simply encoded as two hexadecimal numbers. Zero bytes are not omitted.

Values of Float and Decimal types are encoded as their representation in memory. As we support little-endian architecture, they are encoded in little-endian. Zero leading/trailing bytes are not omitted.

Values of UUID type are encoded as big-endian order string.

Arguments

• arg — A value to convert to hexadecimal. Types: String, UInt, Float, Decimal, Date or DateTime.

Returned value

• A string with the hexadecimal representation of the argument. String.

Examples

Query:

SELECT hex(1);

Result:

01

Query:

SELECT hex(toFloat32(number)) AS hex_presentation FROM numbers(15, 2);

Result:

┌─hex_presentation─┐
│ 00007041         │
│ 00008041         │
└──────────────────┘

Query:

SELECT hex(toFloat64(number)) AS hex_presentation FROM numbers(15, 2);

Result:

┌─hex_presentation─┐
│ 0000000000002E40 │
│ 0000000000003040 │
└──────────────────┘

Query:

SELECT lower(hex(toUUID('61f0c404-5cb3-11e7-907b-a6006ad3dba0'))) AS uuid_hex

Result:

┌─uuid_hex─────────────────────────┐
│ 61f0c4045cb311e7907ba6006ad3dba0 │
└──────────────────────────────────┘

unhex

Performs the opposite operation of hex. It interprets each pair of hexadecimal digits (in the argument) as a number and converts it to the byte represented by the number. The return value is a binary string (BLOB).

If you want to convert the result to a number, you can use the reverse and reinterpretAs<Type> functions.

Note

If unhex is invoked from within the clickhouse-client, binary strings display using UTF-8.

Alias: UNHEX.

Syntax

unhex(arg)

Arguments

• arg — A string containing any number of hexadecimal digits. String, FixedString.

Supports both uppercase and lowercase letters A-F. The number of hexadecimal digits does not have to be even. If it is odd, the last digit is interpreted as the least significant half of the 00-0F byte. If the argument string contains anything other than hexadecimal digits, some implementation-defined result is returned (an exception isn't thrown). For a numeric argument the inverse of hex(N) is not performed by unhex().

Returned value

• A binary string (BLOB). String.

Example

Query:

SELECT unhex('303132'), UNHEX('4D7953514C');

Result:

┌─unhex('303132')─┬─unhex('4D7953514C')─┐
│ 012             │ MySQL               │
└─────────────────┴─────────────────────┘

Query:

SELECT reinterpretAsUInt64(reverse(unhex('FFF'))) AS num;

Result:

┌──num─┐
│ 4095 │
└──────┘

bin

Returns a string containing the argument's binary representation.

Syntax

bin(arg)

Alias: BIN.

For integer arguments, it prints bin digits from the most significant to least significant (big-endian or "human-readable" order). It starts with the most significant non-zero byte (leading zero bytes are omitted) but always prints eight digits of every byte if the leading digit is zero.

Values of type Date and DateTime are formatted as corresponding integers (the number of days since Epoch for Date and the value of Unix Timestamp for DateTime).

For String and FixedString, all bytes are simply encoded as eight binary numbers. Zero bytes are not omitted.

Values of Float and Decimal types are encoded as their representation in memory. As we support little-endian architecture, they are encoded in little-endian. Zero leading/trailing bytes are not omitted.

Values of UUID type are encoded as big-endian order string.

Arguments

• arg — A value to convert to binary. String, FixedString, UInt, Float, Decimal, Date, or DateTime.

Returned value

• A string with the binary representation of the argument. String.

Examples

Query:

SELECT bin(14);

Result:

┌─bin(14)──┐
│ 00001110 │
└──────────┘

Query:

SELECT bin(toFloat32(number)) AS bin_presentation FROM numbers(15, 2);

Result:

┌─bin_presentation─────────────────┐
│ 00000000000000000111000001000001 │
│ 00000000000000001000000001000001 │
└──────────────────────────────────┘

Query:

SELECT bin(toFloat64(number)) AS bin_presentation FROM numbers(15, 2);

Result:

┌─bin_presentation─────────────────────────────────────────────────┐
│ 0000000000000000000000000000000000000000000000000010111001000000 │
│ 0000000000000000000000000000000000000000000000000011000001000000 │
└──────────────────────────────────────────────────────────────────┘

Query:

SELECT bin(toUUID('61f0c404-5cb3-11e7-907b-a6006ad3dba0')) AS bin_uuid

Result:

┌─bin_uuid─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ 01100001111100001100010000000100010111001011001100010001111001111001000001111011101001100000000001101010110100111101101110100000 │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

unbin

Interprets each pair of binary digits (in the argument) as a number and converts it to the byte represented by the number. The functions performs the opposite operation to bin.

Syntax

unbin(arg)

Alias: UNBIN.

For a numeric argument unbin() does not return the inverse of bin(). If you want to convert the result to a number, you can use the reverse and reinterpretAs<Type> functions.

Note

If unbin is invoked from within the clickhouse-client, binary strings are displayed using UTF-8.

Supports binary digits 0 and 1. The number of binary digits does not have to be multiples of eight. If the argument string contains anything other than binary digits, some implementation-defined result is returned (an exception isn't thrown).

Arguments

• arg — A string containing any number of binary digits. String.

Returned value

• A binary string (BLOB). String.

Examples

Query:

SELECT UNBIN('001100000011000100110010'), UNBIN('0100110101111001010100110101000101001100');

Result:

┌─unbin('001100000011000100110010')─┬─unbin('0100110101111001010100110101000101001100')─┐
│ 012                               │ MySQL                                             │
└───────────────────────────────────┴───────────────────────────────────────────────────┘

Query:

SELECT reinterpretAsUInt64(reverse(unbin('1110'))) AS num;

Result:

┌─num─┐
│  14 │
└─────┘

bitmaskToList(num)

Accepts an integer. Returns a string containing the list of powers of two that total the source number when summed. They are comma-separated without spaces in text format, in ascending order.

bitmaskToArray(num)

Accepts an integer. Returns an array of UInt64 numbers containing the list of powers of two that total the source number when summed. Numbers in the array are in ascending order.

bitPositionsToArray(num)

Accepts an integer and converts it to an unsigned integer. Returns an array of UInt64 numbers containing the list of positions of bits of arg that equal 1, in ascending order.

Syntax

bitPositionsToArray(arg)

Arguments

• arg — Integer value. Int/UInt.

Returned value

• An array containing a list of positions of bits that equal 1, in ascending order. Array(UInt64).

Example

Query:

SELECT bitPositionsToArray(toInt8(1)) AS bit_positions;

Result:

┌─bit_positions─┐
│ [0]           │
└───────────────┘

Query:

SELECT bitPositionsToArray(toInt8(-1)) AS bit_positions;

Result:

┌─bit_positions─────┐
│ [0,1,2,3,4,5,6,7] │
└───────────────────┘

mortonEncode

Calculates the Morton encoding (ZCurve) for a list of unsigned integers.

The function has two modes of operation:

• Simple
• Expanded

Simple mode

Accepts up to 8 unsigned integers as arguments and produces a UInt64 code.

Syntax

mortonEncode(args)

Parameters

• args: up to 8 unsigned integers or columns of the aforementioned type.

Returned value

• A UInt64 code. UInt64

Example

Query:

SELECT mortonEncode(1, 2, 3);

Result:

53

Expanded mode

Accepts a range mask (tuple) as a first argument and up to 8 unsigned integers as other arguments.

Each number in the mask configures the amount of range expansion:
1 - no expansion
2 - 2x expansion
3 - 3x expansion
...
Up to 8x expansion.

Syntax

mortonEncode(range_mask, args)

Parameters

• range_mask: 1-8.
• args: up to 8 unsigned integers or columns of the aforementioned type.

Note: when using columns for args the provided range_mask tuple should still be a constant.

Returned value

• A UInt64 code. UInt64

Example

Range expansion can be beneficial when you need a similar distribution for arguments with wildly different ranges (or cardinality) For example: 'IP Address' (0...FFFFFFFF) and 'Country code' (0...FF).

Query:

SELECT mortonEncode((1,2), 1024, 16);

Result:

1572864

Note: tuple size must be equal to the number of the other arguments.

Example

Morton encoding for one argument is always the argument itself:

Query:

SELECT mortonEncode(1);

Result:

1

Example

It is also possible to expand one argument too:

Query:

SELECT mortonEncode(tuple(2), 128);

Result:

32768

Example

You can also use column names in the function.

Query:

First create the table and insert some data.

CREATE TABLE morton_numbers(
    n1 UInt32,
    n2 UInt32,
    n3 UInt16,
    n4 UInt16,
    n5 UInt8,
    n6 UInt8,
    n7 UInt8,
    n8 UInt8
)
ENGINE=MergeTree()
ORDER BY n1 SETTINGS index_granularity = 8192, index_granularity_bytes = '10Mi';
insert into morton_numbers (*) values(1,2,3,4,5,6,7,8);

Use column names instead of constants as function arguments to mortonEncode

Query:

SELECT mortonEncode(n1, n2, n3, n4, n5, n6, n7, n8) FROM morton_numbers;

Result:

2155374165

implementation details

Please note that you can fit only so many bits of information into Morton code as UInt64 has. Two arguments will have a range of maximum 2^32 (64/2) each, three arguments a range of max 2^21 (64/3) each and so on. All overflow will be clamped to zero.

mortonDecode

Decodes a Morton encoding (ZCurve) into the corresponding unsigned integer tuple.

As with the mortonEncode function, this function has two modes of operation:

• Simple
• Expanded

Simple mode

Accepts a resulting tuple size as the first argument and the code as the second argument.

Syntax

mortonDecode(tuple_size, code)

Parameters

• tuple_size: integer value no more than 8.
• code: UInt64 code.

Returned value

• tuple of the specified size. UInt64

Example

Query:

SELECT mortonDecode(3, 53);

Result:

["1","2","3"]

Expanded mode

Accepts a range mask (tuple) as a first argument and the code as the second argument. Each number in the mask configures the amount of range shrink:
1 - no shrink
2 - 2x shrink
3 - 3x shrink
...
Up to 8x shrink.

Range expansion can be beneficial when you need a similar distribution for arguments with wildly different ranges (or cardinality) For example: 'IP Address' (0...FFFFFFFF) and 'Country code' (0...FF). As with the encode function, this is limited to 8 numbers at most.

Example

Query:

SELECT mortonDecode(1, 1);

Result:

["1"]

Example

It is also possible to shrink one argument:

Query:

SELECT mortonDecode(tuple(2), 32768);

Result:

["128"]

Example

You can also use column names in the function.

First create the table and insert some data.

Query:

CREATE TABLE morton_numbers(
    n1 UInt32,
    n2 UInt32,
    n3 UInt16,
    n4 UInt16,
    n5 UInt8,
    n6 UInt8,
    n7 UInt8,
    n8 UInt8
)
ENGINE=MergeTree()
ORDER BY n1 SETTINGS index_granularity = 8192, index_granularity_bytes = '10Mi';
insert into morton_numbers (*) values(1,2,3,4,5,6,7,8);

Use column names instead of constants as function arguments to mortonDecode

Query:

SELECT untuple(mortonDecode(8, mortonEncode(n1, n2, n3, n4, n5, n6, n7, n8))) FROM morton_numbers;

Result:

1    2    3    4    5    6    7    8

hilbertEncode

Calculates code for Hilbert Curve for a list of unsigned integers.

The function has two modes of operation:

• Simple
• Expanded

Simple mode

Simple: accepts up to 2 unsigned integers as arguments and produces a UInt64 code.

Syntax

hilbertEncode(args)

Parameters

• args: up to 2 unsigned integers or columns of the aforementioned type.

Returned value

• A UInt64 code

Type: UInt64

Example

Query:

SELECT hilbertEncode(3, 4);

Result:

31

Expanded mode

Accepts a range mask (tuple) as a first argument and up to 2 unsigned integers as other arguments.

Each number in the mask configures the number of bits by which the corresponding argument will be shifted left, effectively scaling the argument within its range.

Syntax

hilbertEncode(range_mask, args)

Parameters

• range_mask: (tuple)
• args: up to 2 unsigned integers or columns of the aforementioned type.

Note: when using columns for args the provided range_mask tuple should still be a constant.

Returned value

• A UInt64 code

Type: UInt64

Example

Range expansion can be beneficial when you need a similar distribution for arguments with wildly different ranges (or cardinality) For example: 'IP Address' (0...FFFFFFFF) and 'Country code' (0...FF).

Query:

SELECT hilbertEncode((10,6), 1024, 16);

Result:

4031541586602

Note: tuple size must be equal to the number of the other arguments.

Example

For a single argument without a tuple, the function returns the argument itself as the Hilbert index, since no dimensional mapping is needed.

Query:

SELECT hilbertEncode(1);

Result:

1

Example

If a single argument is provided with a tuple specifying bit shifts, the function shifts the argument left by the specified number of bits.

Query:

SELECT hilbertEncode(tuple(2), 128);

Result:

512

Example

The function also accepts columns as arguments:

Query:

First create the table and insert some data.

CREATE TABLE hilbert_numbers(
    n1 UInt32,
    n2 UInt32
)
ENGINE=MergeTree()
ORDER BY n1 SETTINGS index_granularity = 8192, index_granularity_bytes = '10Mi';
insert into hilbert_numbers (*) values(1,2);

Use column names instead of constants as function arguments to hilbertEncode

Query:

SELECT hilbertEncode(n1, n2) FROM hilbert_numbers;

Result:

13

implementation details

Please note that you can fit only so many bits of information into Hilbert code as UInt64 has. Two arguments will have a range of maximum 2^32 (64/2) each. All overflow will be clamped to zero.

hilbertDecode

Decodes a Hilbert curve index back into a tuple of unsigned integers, representing coordinates in multi-dimensional space.

As with the hilbertEncode function, this function has two modes of operation:

• Simple
• Expanded

Simple mode

Accepts up to 2 unsigned integers as arguments and produces a UInt64 code.

Syntax

hilbertDecode(tuple_size, code)

Parameters

• tuple_size: integer value no more than 2.
• code: UInt64 code.

Returned value

• tuple of the specified size.

Type: UInt64

Example

Query:

SELECT hilbertDecode(2, 31);

Result:

["3", "4"]

Expanded mode

Accepts a range mask (tuple) as a first argument and up to 2 unsigned integers as other arguments. Each number in the mask configures the number of bits by which the corresponding argument will be shifted left, effectively scaling the argument within its range.

Range expansion can be beneficial when you need a similar distribution for arguments with wildly different ranges (or cardinality) For example: 'IP Address' (0...FFFFFFFF) and 'Country code' (0...FF). As with the encode function, this is limited to 8 numbers at most.

Example

Hilbert code for one argument is always the argument itself (as a tuple).

Query:

SELECT hilbertDecode(1, 1);

Result:

["1"]

Example

A single argument with a tuple specifying bit shifts will be right-shifted accordingly.

Query:

SELECT hilbertDecode(tuple(2), 32768);

Result:

["128"]

Example

The function accepts a column of codes as a second argument:

First create the table and insert some data.

Query:

CREATE TABLE hilbert_numbers(
    n1 UInt32,
    n2 UInt32
)
ENGINE=MergeTree()
ORDER BY n1 SETTINGS index_granularity = 8192, index_granularity_bytes = '10Mi';
insert into hilbert_numbers (*) values(1,2);

Use column names instead of constants as function arguments to hilbertDecode

Query:

SELECT untuple(hilbertDecode(2, hilbertEncode(n1, n2))) FROM hilbert_numbers;

Result:

1    2

bech32Encode

Encodes a binary data string, along with a human-readable part (HRP), using the Bech32 or Bech32m algorithms.

Syntax

bech32Encode(hrp, data[, witver])

Parameters

• hrp — String of 1 - 83 lowercase characters specifying the "human-readable part" of the code. Usually 'bc' or 'tb'. String or FixedString.
• data — String of binary data to encode. String or FixedString.
• witver - Witness version. Optional, default = 1. An UInt* specifying the version of the algorithm to run. 0 for Bech32 and 1 or greater for Bech32m.

Note

When using the FixedString data type, if a value does not fully fill the row it is padded with null characters. While the bech32Encode function will handle this automatically for the hrp argument, for the data argument the values must not be padded. For this reason it is not recommended to use the FixedString data type for your data values unless you are certain that they are all the same length and ensure that your FixedString column is set to that length as well.

Returned value

• A Bech32 address string, consisting of the human-readable part, a separator character which is always '1', and a data part. The length of the string will never exceed 90 characters. If the algorithm cannot generate a valid address from the input, it will return an empty string.

Type: String.

Example

When no witness version is supplied, the default is 1, the updated Bech32m algorithm.

Query:

SELECT bech32Encode('bc', unhex('751e76e8199196d454941c45d1b3a323f1433bd6'));

Result:

bc1w508d6qejxtdg4y5r3zarvary0c5xw7k8zcwmq

A witness version of 0 will result in a different address string.

Query:

SELECT bech32Encode('bc', unhex('751e76e8199196d454941c45d1b3a323f1433bd6'), 0);

Result:

bc1w508d6qejxtdg4y5r3zarvary0c5xw7kj7gz7z

While 'bc' (Mainnet) and 'tb' (Testnet) are the only allowed hrp values for the SegWit address format, Bech32 allows any hrp that satisfies the above requirements.

Query:

SELECT bech32Encode('abcdefg', unhex('751e76e8199196d454941c45d1b3a323f1433bd6'), 10);

Result:

abcdefg1w508d6qejxtdg4y5r3zarvary0c5xw7k9rp8r4

bech32Decode

Decodes a Bech32 address string generated by either the bech32 or bech32m algorithms.

Syntax

bech32Decode(address)

Parameters

• address — Bech32 string to decode. String or FixedString.

Note

Unlike the encode function, Bech32Decode will automatically handle padded FixedStrings.

Returned value

• A tuple consisting of the (hrp, data) that was used to encode the string. The data is in binary format.

Type: (String, String).

Example

Query:

SELECT tup.1 AS hrp, hex(tup.2) AS data FROM (SELECT bech32Decode('bc1w508d6qejxtdg4y5r3zarvary0c5xw7kj7gz7z') AS tup);

Result:

bc   751E76E8199196D454941C45D1B3A323F1433BD6

Query:

SELECT tup.1 AS hrp, hex(tup.2) AS data FROM (SELECT bech32Decode('tb1w508d6qejxtdg4y5r3zarvary0c5xw7kzp034v') AS tup);

Result:

tb   751E76E8199196D454941C45D1B3A323F1433BD6

bech32Decode

Introduced in: v25.6

Decodes a Bech32 address string generated by either the bech32 or bech32m algorithms.

Note

Unlike the encode function, Bech32Decode will automatically handle padded FixedStrings.

Syntax

bech32Decode(address)

Arguments

• address — A Bech32 string to decode. String or FixedString

Returned value

Returns a tuple consisting of (hrp, data) that was used to encode the string. The data is in binary format. Tuple(String, String)

Examples

Decode address

SELECT tup.1 AS hrp, hex(tup.2) AS data FROM (SELECT bech32Decode('bc1w508d6qejxtdg4y5r3zarvary0c5xw7kj7gz7z') AS tup)

bc   751E76E8199196D454941C45D1B3A323F1433BD6

Testnet address

SELECT tup.1 AS hrp, hex(tup.2) AS data FROM (SELECT bech32Decode('tb1w508d6qejxtdg4y5r3zarvary0c5xw7kzp034v') AS tup)

tb   751E76E8199196D454941C45D1B3A323F1433BD6

bech32Encode

Introduced in: v25.6

Encodes a binary data string, along with a human-readable part (HRP), using the Bech32 or Bech32m algorithms.

Note

When using the FixedString data type, if a value does not fully fill the row it is padded with null characters. While the bech32Encode function will handle this automatically for the hrp argument, for the data argument the values must not be padded. For this reason it is not recommended to use the FixedString data type for your data values unless you are certain that they are all the same length and ensure that your FixedString column is set to that length as well.

Syntax

bech32Encode(hrp, data[, witver])

Arguments

• hrp — A String of 1 - 83 lowercase characters specifying the "human-readable part" of the code. Usually 'bc' or 'tb'. String or FixedString
• data — A String of binary data to encode. String or FixedString
• witver — Optional. The witness version (default = 1). An UInt* specifying the version of the algorithm to run. 0 for Bech32 and 1 or greater for Bech32m. UInt*

Returned value

Returns a Bech32 address string, consisting of the human-readable part, a separator character which is always '1', and a data part. The length of the string will never exceed 90 characters. If the algorithm cannot generate a valid address from the input, it will return an empty string. String

Examples

Default Bech32m

-- When no witness version is supplied, the default is 1, the updated Bech32m algorithm.
SELECT bech32Encode('bc', unhex('751e76e8199196d454941c45d1b3a323f1433bd6'))

bc1w508d6qejxtdg4y5r3zarvary0c5xw7k8zcwmq

Bech32 algorithm

-- A witness version of 0 will result in a different address string.
SELECT bech32Encode('bc', unhex('751e76e8199196d454941c45d1b3a323f1433bd6'), 0)

bc1w508d6qejxtdg4y5r3zarvary0c5xw7kj7gz7z

Custom HRP

-- While 'bc' (Mainnet) and 'tb' (Testnet) are the only allowed hrp values for the
-- SegWit address format, Bech32 allows any hrp that satisfies the above requirements.
SELECT bech32Encode('abcdefg', unhex('751e76e8199196d454941c45d1b3a323f1433bd6'), 10)

abcdefg1w508d6qejxtdg4y5r3zarvary0c5xw7k9rp8r4

bin

Introduced in: v21.8

Returns a string containing the argument's binary representation according to the following logic for different types:

Type	Description
(U)Int*	Prints bin digits from the most significant to least significant (big-endian or "human-readable" order). It starts with the most significant non-zero byte (leading zero bytes are omitted) but always prints eight digits of every byte if the leading digit is zero.
Date and DateTime	Formatted as corresponding integers (the number of days since epoch for Date and the value of unix timestamp for DateTime).
String and FixedString	All bytes are simply encoded as eight binary numbers. Zero bytes are not omitted.
Float* and Decimal	Encoded as their representation in memory. As we support little-endian architecture, they are encoded in little-endian. Zero leading/trailing bytes are not omitted.
UUID	Encoded as big-endian order string.

Syntax

bin(arg)

Arguments

• arg — A value to convert to binary. String or FixedString or (U)Int* or Float* or Decimal or Date or DateTime

Returned value

Returns a string with the binary representation of the argument. String

Examples

Simple integer

SELECT bin(14)

┌─bin(14)──┐
│ 00001110 │
└──────────┘

Float32 numbers

SELECT bin(toFloat32(number)) AS bin_presentation FROM numbers(15, 2)

┌─bin_presentation─────────────────┐
│ 00000000000000000111000001000001 │
│ 00000000000000001000000001000001 │
└──────────────────────────────────┘

Float64 numbers

SELECT bin(toFloat64(number)) AS bin_presentation FROM numbers(15, 2)

┌─bin_presentation─────────────────────────────────────────────────┐
│ 0000000000000000000000000000000000000000000000000010111001000000 │
│ 0000000000000000000000000000000000000000000000000011000001000000 │
└──────────────────────────────────────────────────────────────────┘

UUID conversion

SELECT bin(toUUID('61f0c404-5cb3-11e7-907b-a6006ad3dba0')) AS bin_uuid

┌─bin_uuid─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ 01100001111100001100010000000100010111001011001100010001111001111001000001111011101001100000000001101010110100111101101110100000 │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

bitPositionsToArray

Introduced in: v21.7

This function returns the positions (in ascending order) of the 1 bits in the binary representation of an unsigned integer. Signed input integers are first casted to an unsigned integer.

Syntax

bitPositionsToArray(arg)

Arguments

• arg — An integer value. (U)Int*

Returned value

Returns an array with the ascendingly ordered positions of 1 bits in the binary representation of the input. Array(UInt64)

Examples

Single bit set

SELECT bitPositionsToArray(toInt8(1)) AS bit_positions

┌─bit_positions─┐
│ [0]           │
└───────────────┘

All bits set

SELECT bitPositionsToArray(toInt8(-1)) AS bit_positions

┌─bit_positions─────────────┐
│ [0, 1, 2, 3, 4, 5, 6, 7]  │
└───────────────────────────┘

bitmaskToArray

Introduced in: v1.1

This function decomposes an integer into a sum of powers of two. The powers of two are returned as an ascendingly ordered array.

Syntax

bitmaskToArray(num)

Arguments

• num — An integer value. (U)Int*

Returned value

Returns an array with the ascendingly ordered powers of two which sum up to the input number. Array(UInt64)

Examples

Basic example

SELECT bitmaskToArray(50) AS powers_of_two

┌─powers_of_two───┐
│ [2, 16, 32]     │
└─────────────────┘

Single power of two

SELECT bitmaskToArray(8) AS powers_of_two

┌─powers_of_two─┐
│ [8]           │
└───────────────┘

bitmaskToList

Introduced in: v1.1

Like bitmaskToArray but returns the powers of two as a comma-separated string.

Syntax

bitmaskToList(num)

Arguments

• num — An integer value. (U)Int*

Returned value

Returns a string containing comma-separated powers of two. String

Examples

Basic example

SELECT bitmaskToList(50) AS powers_list

┌─powers_list───┐
│ 2, 16, 32     │
└───────────────┘

char

Introduced in: v20.1

Returns a string with length equal to the number of arguments passed where each byte has the value of the corresponding argument. Accepts multiple arguments of numeric types.

If the value of the argument is out of range of the UInt8 data type, then it is converted to UInt8 with potential rounding and overflow.

Syntax

char(num1[, num2[, ...]]);

Arguments

• num1[, num2[, num3 ...]] — Numerical arguments interpreted as integers. (U)Int8/16/32/64 or Float*

Returned value

Returns a string of the given bytes. String

Examples

Basic example

SELECT char(104.1, 101, 108.9, 108.9, 111) AS hello;

┌─hello─┐
│ hello │
└───────┘

Constructing arbitrary encodings

-- You can construct a string of arbitrary encoding by passing the corresponding bytes.
-- for example UTF8
SELECT char(0xD0, 0xBF, 0xD1, 0x80, 0xD0, 0xB8, 0xD0, 0xB2, 0xD0, 0xB5, 0xD1, 0x82) AS hello;

┌─hello──┐
│ привет │
└────────┘

hex

Introduced in: v1.1

Returns a string containing the argument's hexadecimal representation according to the following logic for different types:

Type	Description
(U)Int*	Prints hex digits ("nibbles") from the most significant to least significant (big-endian or "human-readable" order). It starts with the most significant non-zero byte (leading zero bytes are omitted) but always prints both digits of every byte even if the leading digit is zero.
Date and DateTime	Formatted as corresponding integers (the number of days since epoch for Date and the value of unix timestamp for DateTime).
String and FixedString	All bytes are simply encoded as two hexadecimal numbers. Zero bytes are not omitted.
Float* and Decimal	Encoded as their representation in memory. ClickHouse represents the values internally always as little endian, therefore they are encoded as such. Zero leading/trailing bytes are not omitted.
UUID	Encoded as big-endian order string.

The function uses uppercase letters A-F and not using any prefixes (like 0x) or suffixes (like h).

Syntax

hex(arg)

Arguments

• arg — A value to convert to hexadecimal. String or (U)Int* or Float* or Decimal or Date or DateTime

Returned value

Returns a string with the hexadecimal representation of the argument. String

Examples

Simple integer

SELECT hex(1)

01

Float32 numbers

SELECT hex(toFloat32(number)) AS hex_presentation FROM numbers(15, 2)

┌─hex_presentation─┐
│ 00007041         │
│ 00008041         │
└──────────────────┘

Float64 numbers

SELECT hex(toFloat64(number)) AS hex_presentation FROM numbers(15, 2)

┌─hex_presentation─┐
│ 0000000000002E40 │
│ 0000000000003040 │
└──────────────────┘

UUID conversion

SELECT lower(hex(toUUID('61f0c404-5cb3-11e7-907b-a6006ad3dba0'))) AS uuid_hex

┌─uuid_hex─────────────────────────┐
│ 61f0c4045cb311e7907ba6006ad3dba0 │
└──────────────────────────────────┘

hilbertDecode

Introduced in: v24.6

Decodes a Hilbert curve index back into a tuple of unsigned integers, representing coordinates in multi-dimensional space.

As with the hilbertEncode function, this function has two modes of operation:

• Simple
• Expanded

Simple mode

Accepts up to 2 unsigned integers as arguments and produces a UInt64 code.

Expanded mode

Accepts a range mask (tuple) as a first argument and up to 2 unsigned integers as other arguments. Each number in the mask configures the number of bits by which the corresponding argument will be shifted left, effectively scaling the argument within its range.

Range expansion can be beneficial when you need a similar distribution for arguments with wildly different ranges (or cardinality) For example: 'IP Address' (0...FFFFFFFF) and 'Country code' (0...FF). As with the encode function, this is limited to 8 numbers at most.

Syntax

hilbertDecode(tuple_size, code)

Arguments

• tuple_size — Integer value of no more than 2. UInt8/16/32/64 or Tuple(UInt8/16/32/64)
• code — UInt64 code. UInt64

Returned value

Returns a tuple of the specified size. Tuple(UInt64)

Examples

Simple mode

SELECT hilbertDecode(2, 31)

["3", "4"]

Single argument

-- Hilbert code for one argument is always the argument itself (as a tuple).
SELECT hilbertDecode(1, 1)

["1"]

Expanded mode

-- A single argument with a tuple specifying bit shifts will be right-shifted accordingly.
SELECT hilbertDecode(tuple(2), 32768)

["128"]

Column usage

-- First create the table and insert some data
CREATE TABLE hilbert_numbers(
    n1 UInt32,
    n2 UInt32
)
ENGINE=MergeTree()
ORDER BY n1 SETTINGS index_granularity = 8192, index_granularity_bytes = '10Mi';
insert into hilbert_numbers (*) values(1,2);

-- Use column names instead of constants as function arguments
SELECT untuple(hilbertDecode(2, hilbertEncode(n1, n2))) FROM hilbert_numbers;

1    2

hilbertEncode

Introduced in: v24.6

Calculates code for Hilbert Curve for a list of unsigned integers.

The function has two modes of operation:

• Simple
• Expanded

Simple mode

Accepts up to 2 unsigned integers as arguments and produces a UInt64 code.

Expanded mode

Accepts a range mask (Tuple) as the first argument and up to 2 unsigned integers as other arguments.

Each number in the mask configures the number of bits by which the corresponding argument will be shifted left, effectively scaling the argument within its range.

Syntax

-- Simplified mode
hilbertEncode(args)

-- Expanded mode
hilbertEncode(range_mask, args)

Arguments

• args — Up to two UInt values or columns of type UInt. UInt8/16/32/64
• range_mask — For the expanded mode, up to two UInt values or columns of type UInt. UInt8/16/32/64

Returned value

Returns a UInt64 code. UInt64

Examples

Simple mode

SELECT hilbertEncode(3, 4)

31

Expanded mode

-- Range expansion can be beneficial when you need a similar distribution for
-- arguments with wildly different ranges (or cardinality).
-- For example: 'IP Address' (0...FFFFFFFF) and 'Country code' (0...FF).
-- Note: tuple size must be equal to the number of the other arguments.
SELECT hilbertEncode((10, 6), 1024, 16)

4031541586602

Single argument

-- For a single argument without a tuple, the function returns the argument
-- itself as the Hilbert index, since no dimensional mapping is needed.
SELECT hilbertEncode(1)

1

Expanded single argument

-- If a single argument is provided with a tuple specifying bit shifts, the function
-- shifts the argument left by the specified number of bits.
SELECT hilbertEncode(tuple(2), 128)

512

Column usage

-- First create the table and insert some data
CREATE TABLE hilbert_numbers(
    n1 UInt32,
    n2 UInt32
)
ENGINE=MergeTree()
ORDER BY n1;
insert into hilbert_numbers (*) values(1, 2);

-- Use column names instead of constants as function arguments
SELECT hilbertEncode(n1, n2) FROM hilbert_numbers;

13

mortonDecode

Introduced in: v24.6

Decodes a Morton encoding (ZCurve) into the corresponding unsigned integer tuple.

As with the mortonEncode function, this function has two modes of operation:

• Simple
• Expanded

Simple mode

Accepts a resulting tuple size as the first argument and the code as the second argument.

Expanded mode

Accepts a range mask (tuple) as the first argument and the code as the second argument. Each number in the mask configures the amount of range shrink:

• 1 - no shrink
• 2 - 2x shrink
• 3 - 3x shrink ⋮
• Up to 8x shrink.

Range expansion can be beneficial when you need a similar distribution for arguments with wildly different ranges (or cardinality). For example: 'IP Address' (0...FFFFFFFF) and 'Country code' (0...FF). As with the encode function, this is limited to 8 numbers at most.

Syntax

-- Simple mode
mortonDecode(tuple_size, code)

-- Expanded mode
mortonDecode(range_mask, code)

Arguments

• tuple_size — Integer value no more than 8. UInt8/16/32/64
• range_mask — For the expanded mode, the mask for each argument. The mask is a tuple of unsigned integers. Each number in the mask configures the amount of range shrink. Tuple(UInt8/16/32/64)
• code — UInt64 code. UInt64

Returned value

Returns a tuple of the specified size. Tuple(UInt64)

Examples

Simple mode

SELECT mortonDecode(3, 53)

["1", "2", "3"]

Single argument

SELECT mortonDecode(1, 1)

["1"]

Expanded mode, shrinking one argument

SELECT mortonDecode(tuple(2), 32768)

["128"]

Column usage

-- First create the table and insert some data
CREATE TABLE morton_numbers(
    n1 UInt32,
    n2 UInt32,
    n3 UInt16,
    n4 UInt16,
    n5 UInt8,
    n6 UInt8,
    n7 UInt8,
    n8 UInt8
)
ENGINE=MergeTree()
ORDER BY n1;
INSERT INTO morton_numbers (*) values(1, 2, 3, 4, 5, 6, 7, 8);

-- Use column names instead of constants as function arguments
SELECT untuple(mortonDecode(8, mortonEncode(n1, n2, n3, n4, n5, n6, n7, n8))) FROM morton_numbers;

1 2 3 4 5 6 7 8

mortonEncode

Introduced in: v24.6

Calculates the Morton encoding (ZCurve) for a list of unsigned integers.

The function has two modes of operation:

• Simple
• Expanded*

Simple mode

Accepts up to 8 unsigned integers as arguments and produces a UInt64 code.

Expanded mode

Accepts a range mask (Tuple) as the first argument and up to 8 unsigned integers as other arguments.

Each number in the mask configures the amount of range expansion:

• 1 - no expansion
• 2 - 2x expansion
• 3 - 3x expansion ⋮
• Up to 8x expansion.

Syntax

-- Simplified mode
mortonEncode(args)

-- Expanded mode
mortonEncode(range_mask, args)

Arguments

• args — Up to 8 unsigned integers or columns of the aforementioned type. UInt8/16/32/64
• range_mask — For the expanded mode, the mask for each argument. The mask is a tuple of unsigned integers from 1 - 8. Each number in the mask configures the amount of range shrink. Tuple(UInt8/16/32/64)

Returned value

Returns a UInt64 code. UInt64

Examples

Simple mode

SELECT mortonEncode(1, 2, 3)

53

Expanded mode

-- Range expansion can be beneficial when you need a similar distribution for
-- arguments with wildly different ranges (or cardinality)
-- For example: 'IP Address' (0...FFFFFFFF) and 'Country code' (0...FF).
-- Note: the Tuple size must be equal to the number of the other arguments.
SELECT mortonEncode((1,2), 1024, 16)

1572864

Single argument

-- Morton encoding for one argument is always the argument itself
SELECT mortonEncode(1)

1

Expanded single argument

SELECT mortonEncode(tuple(2), 128)

32768

Column usage

-- First create the table and insert some data
CREATE TABLE morton_numbers(
    n1 UInt32,
    n2 UInt32,
    n3 UInt16,
    n4 UInt16,
    n5 UInt8,
    n6 UInt8,
    n7 UInt8,
    n8 UInt8
)
ENGINE=MergeTree()
ORDER BY n1;
INSERT INTO morton_numbers (*) values(1, 2, 3, 4, 5, 6, 7, 8);

-- Use column names instead of constants as function arguments
SELECT mortonEncode(n1, n2, n3, n4, n5, n6, n7, n8) FROM morton_numbers;

2155374165

sqidDecode

Introduced in: v

Transforms a Sqid back into an array of numbers.

Syntax

sqidDecode(number1, ...)

Arguments

• sqid — A sqid

Returned value

An array of numbers Array(UInt64)

Examples

simple

SELECT sqidDecode('gXHfJ1C6dN');

┌─sqidDecode('gXHfJ1C6dN')─┐
│ [1,2,3,4,5]              │
└──────────────────────────┘

sqidEncode

Introduced in: v

Transforms numbers into a Sqid which is a Youtube-like ID string.

Syntax

sqidEncode(number1, ...)

Arguments

• number1, ... — Arbitrarily many numbers. UInt8/16/32/64

Returned value

A hash id String

Examples

simple

SELECT sqidEncode(1, 2, 3, 4, 5);

┌─sqidEncode(1, 2, 3, 4, 5)─┐
│ gXHfJ1C6dN                │
└───────────────────────────┘

unbin

Introduced in: v21.8

Interprets each pair of binary digits (in the argument) as a number and converts it to the byte represented by the number. The functions performs the opposite operation to bin.

For a numeric argument unbin() does not return the inverse of bin(). If you want to convert the result to a number, you can use the reverse and reinterpretAs<Type> functions.

Note

If unbin is invoked from within the clickhouse-client, binary strings are displayed using UTF-8.

Supports binary digits 0 and 1. The number of binary digits does not have to be multiples of eight. If the argument string contains anything other than binary digits, the result is undefined (no exception is thrown).

Syntax

unbin(arg)

Arguments

• arg — A string containing any number of binary digits. String

Returned value

Returns a binary string (BLOB). String

Examples

Basic usage

SELECT UNBIN('001100000011000100110010'), UNBIN('0100110101111001010100110101000101001100')

┌─unbin('001100000011000100110010')─┬─unbin('0100110101111001010100110101000101001100')─┐
│ 012                               │ MySQL                                             │
└───────────────────────────────────┴───────────────────────────────────────────────────┘

Convert to number

SELECT reinterpretAsUInt64(reverse(unbin('1110'))) AS num

┌─num─┐
│  14 │
└─────┘

unhex

Introduced in: v1.1

Performs the opposite operation of hex. It interprets each pair of hexadecimal digits (in the argument) as a number and converts it to the byte represented by the number. The returned value is a binary string (BLOB).

If you want to convert the result to a number, you can use the reverse and reinterpretAs<Type> functions.

Note

clickhouse-client interprets strings as UTF-8. This may cause that values returned by hex to be displayed surprisingly.

Supports both uppercase and lowercase letters A-F. The number of hexadecimal digits does not have to be even. If it is odd, the last digit is interpreted as the least significant half of the 00-0F byte. If the argument string contains anything other than hexadecimal digits, some implementation-defined result is returned (an exception isn't thrown). For a numeric argument the inverse of hex(N) is not performed by unhex().

Syntax

unhex(arg)

Arguments

• arg — A string containing any number of hexadecimal digits. String or FixedString

Returned value

Returns a binary string (BLOB). String

Examples

Basic usage

SELECT unhex('303132'), UNHEX('4D7953514C')

┌─unhex('303132')─┬─unhex('4D7953514C')─┐
│ 012             │ MySQL               │
└─────────────────┴─────────────────────┘

Convert to number

SELECT reinterpretAsUInt64(reverse(unhex('FFF'))) AS num

┌──num─┐
│ 4095 │
└──────┘