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SUBSTRING

The SQL SUBSTRING function is used to extract a part of a string, where you can specify the start position and the length of the text. This function can be very beneficial when you only need a specific part of a string.

Syntax​

The standardized SQL syntax for SUBSTRING is as follows:

SUBSTRING(string, start, length)

Where:

  • string is the source string from which you want to extract.
  • start is the position to start extraction from. The first position in the string is always 1.
  • length is the number of characters to extract.

Usage​

For instance, if you want to extract the first 5 characters from the string 'Hello World':

SELECT SUBSTRING('Hello World', 1, 5) as ExtractedString;

Result:

| ExtractedString |
| --------------- |
| Hello           |

You can also use SUBSTRING on table columns, like so:

SELECT SUBSTRING(column_name, start, length) FROM table_name;

SUBSTRING with FROM and FOR​

In some database systems (like PostgreSQL and SQL Server), the SUBSTRING function uses a different syntax:

SUBSTRING(string FROM start FOR length)

This format functions the same way as the previously mentioned syntax.

For example:

SELECT SUBSTRING('Hello World' FROM 1 FOR 5) as ExtractedString;

This would yield the same result as the previous example - 'Hello'.

Note​

SQL is case-insensitive, meaning SUBSTRING, substring, and Substring will all function the same way.