SUBSTRING() function

Substring() extracts a substring value from a specified string based on a designated start index and optional length.

Syntax

substring(expr,startIndex,length)

Arguments

Argument	Description	Data type	Return value
`expr`	Input `string` used to extract a substring
`startIndex`	Required `int` value for the starting index of the substring in the evaluated expression. Starts from zero.
`length`	Optional `int` value that represents the length of the substring to extract. Defaults to end of evaluated `expr`.

Returns

Data type	Value
`string`	Returns a substring based on the `startIndex` value and optional `length`.

Examples

Substring of the string in a column

create table segments
    (_id id, segment string);

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

select _id, substring(segment,0,3) as substr from segments;
+-----+----------+
| _id | substr   |
+-----+----------+
|   1 | gre      |
+-----+----------+

Substring of a reversed string

create table segments
    (_id id, segment string);

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

select _id, substring(reverse(segment), 1) as substr from segments;
+-----+----------+
| _id | substr   |
+-----+----------+
|   1 | er       |
+-----+----------+