PREFIX() function

PREFIX() function returns a substring of a given length, starting from the beginning of the provided string.

Syntax

prefix(expr, length)

Arguments

Argument	Data type	Description	Required	Additional information
`expr`	string	String value or any expression that resolves to a string	Yes
`length`	int	Length of the prefix to extract	Yes

Returns

Data type	Value
`string`	A prefix substring extracted from `expr` of length `length`

Examples

Convert strings in a column to a prefix

create table segments
    (_id id, segment string);

insert into segments(_id,segment)
    values (1,'FOOBAR')

select _id, prefix(segment, 3) as convertedstr from segments;
+-----+---------------+
| _id | convertedstr  |
+-----+---------------+
|   1 | FOO           |
+-----+---------------+