To declare a variable, we need to start with DO$$.<\/p>\n
In the declare section or between the “begin end” blocks, we write the name and data type of our variable and define its value with “:=”.<\/p>\n
The output of the variable can be printed on the screen by typing the variable declared with the ‘%’ sign after the RAISE NOTICE.<\/p>\n
![](\"http:\/\/www.farukerdem.com\/wp-content\/uploads\/2020\/12\/postgresqldeclare.png\")
<\/p>\n
In RAISE NOTICE, after writing what you want to write before the variable inside the quotation marks, you need to write the % sign since we are using a single variable.<\/p>\n
You can use it for multiple variables as follows.<\/p>\n
![](\"http:\/\/www.farukerdem.com\/wp-content\/uploads\/2020\/12\/declarepostgresql1.png\")
<\/p>\n
Another different use is to declare session-based variables.<\/p>\n
Example usage is as follows.<\/p>\n
![](\"http:\/\/www.farukerdem.com\/wp-content\/uploads\/2020\/12\/declarepostgresql2.png\")
<\/p>\n
In the above example, it will bring the record in the veliler table according to the variable value entered.<\/p>\n