How to use substring in SQL to extract part of a string.

In SQL, the SUBSTRING function can be used to extract a portion of a string.

The syntax of the SUBSTRING function is as follows:

Extract a portion of the string starting from a specified position with a specified length.

In this case, “string” refers to the string that needs to be extracted from, “start_position” indicates the starting point for extraction, and “length” represents the number of characters to be extracted.

Here are some examples:

If we have a string ‘Hello World’ and want to extract 5 characters starting from the 7th character, we can use the following statement:

The output result is ‘World’.

To extract a portion of a string, you can use the following statement:

The output result is ‘Hello’.

If the length parameter is not specified, the string will be truncated from the start_position to the end.

The output is ‘World’.

Please use the SUBSTRING function according to the specific syntax of the database you are using, as different databases such as MySQL and PostgreSQL may have different indexes for this function (starting from 1 or 0).