PostgreSQL substring function.

Preamble

PostgreSQL substring function allows extracting substring from a string.

Syntax of the substring function in PostgreSQL

substring( string [from start_position] [for length] )

Parameters and function arguments

• string – Source line.
• start_position – Optional. This is the initial position to extract. If this parameter is not specified, the substring function will start from position 1 (which is the first position in the string).
• length – Optional. This is the number of characters to be extracted. If this parameter is not specified, the substring function will return the whole line (from start_position to the end of the string).

Note:

• The first position in the string is 1.

The substring function can be used in the following PostgreSQL versions

PostgreSQL 11, PostgreSQL 10, PostgreSQL 9.6, PostgreSQL 9.5, PostgreSQL 9.4, PostgreSQL 9.3, PostgreSQL 9.2, PostgreSQL 9.1, PostgreSQL 9.0, PostgreSQL 8.4.

Consider some examples of the substring function to understand how to use the substring function in PostgreSQL.
For example:

SELECT substring('Google.com' for 6);

--Result: Google

SELECT substring('Google.com' from 1 to 6);

--Result: Google

SELECT substring('Google.com' from 2 for 5);

--Result: oogle

SELECT substring('Google.com' from 5 to 8);

--Result: le.com

SELECT substring('Google.com' from 8 to 3);

--Result: com

SELECT substring('Google.com' from 8);

--Result: com

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