ekuiper-new/docs/en_US/sqls/functions/transform_functions.md

Transform Functions

Transform functions manipulate data in various ways like convert types, encode with base 64 and compression.

CAST

cast(col, dataType)

Converts a value from one data type to another. The supported types include: bigint, float, string, boolean, bytea and datetime.

Cast to datetime

When casting to a datetime type, the supported column type and casting rule are:

1. If a column is datetime type, just return the value.
2. If column is bigint or float type, the number will be treated as the milliseconds elapsed since January 1, 1970 00: 00:00 UTC and converted.
3. If column is string, it will be parsed to datetime with the default format: "2006-01-02T15:04:05.000Z07:00".
4. Other types are not supported.

ENCODE

encode(col, encodeType)

Use the encode function to encode the payload, which potentially might be non-JSON data, into its string representation based on the encoding scheme. Currently, only "base64" encoding type is supported.

DECODE

decode(col, encodeType)

Decode the input string with specified decoding method. Currently, only "base64" encoding type is supported.

COMPRESS

compress(input, method)

Compress the input string or binary value with a compression method. Currently, 'zlib', 'gzip', 'flate' and 'zstd' method are supported.

DECOMPRESS

decompress(input, method)

Decompress the input string or binary value with a compression method. Currently, 'zlib', 'gzip', 'flate' and 'zstd' method are supported.

TRUNC

trunc(dec, int)

Truncates the first argument to the number of Decimal places specified by the second argument. If the second argument is less than zero, it is set to zero. If the second argument is greater than 34, it is set to 34. Trailing zeroes are stripped from the result.

CHR

chr(col)

Returns the ASCII character that corresponds to the given Int argument.

HEX2DEC

hex2dec(col)

Returns the decimal value of the given hexadecimal string. The data type of the parameter needs to be string. If the parameter is "0x10" or "10", convert it to 16.

DEC2HEX

dec2hex(col)

Returns the hexadecimal string of the given Int type decimal, if the parameter is 16, convert it to "0x10".