PostgreSQL Substring Guide

To extract a substring in PostgreSQL, you can use the SUBSTRING function. The specific syntax is as follows:

SELECT SUBSTRING(column_name FROM start_position [FOR length])
FROM table_name;

In this case, column_name refers to the name of the column to be extracted, start_position indicates the starting position of the extraction (starting from 1), and length is the number of characters to be extracted (optional parameter, if not specified, it will extract to the end of the string). For example, to extract 5 characters starting from the 3rd character in a string column named text from a table called text_column, you can use the following statement:

SELECT SUBSTRING(text FROM 3 FOR 5)
FROM text_column;