SUBSTRING function

Returns the substring of an expression that starts at a position and is of a certain length.

Syntax

SUBSTRING(expression, position, length)

expression: The string.
position: The 1-based index from which the substring starts.
length: The length of the substring. If omitted, it will go until the end of the expression.

A VARCHAR.

> SELECT SUBSTRING('abc', 1);
  'abc'

> SELECT SUBSTRING('abc', 1, 1);
  'a'

> SELECT SUBSTRING('abc', 5);
  ''

Negative integer literals: These are not supported in any environment.
Functional negative positions: It is possible to have a negative position when using a function.
Vertica: These start from the imaginary places before the actual start of the string.
- Example: abc with a position of -1 and length of 3 returns a.
Spark-based engine: These start counting backwards from the end of the string.
- Example: abc with a position of -2 and length of 2 returns bc.

Negative integer literals: These are not supported.
Functional negative lengths: It is possible to have a negative length when using a function.
Vertica: These will throw an exception.
Spark-based engine: These will return an empty string.