Function in SQL

There are two type of function in sql

SQL aggregate function

1) AVG() - Returns the average value

    SELECT AVG(column_name) FROM table_name

2) COUNT() - Returns the number of rows

    SELECT COUNT(column_name) FROM table_name;

3) FIRST() - Returns the first value

    SELECT FIRST(column_name) FROM table_name;

4) LAST() - Returns the last value

SELECT LAST(column_name) FROM table_name;

5) MAX() - Returns the largest value

 SELECT MAX(column_name) FROM table_name;

6) MIN() - Returns the smallest value

SELECT MIN(column_name) FROM table_name;

7) SUM() - Returns the sum

SELECT SUM(column_name) FROM table_name;

SQL scalar function

1) UCASE() - Converts a field to upper case

    SELECT UCASE(column_name) FROM table_name;

2) LCASE() - Converts a field to lower case

    SELECT LCASE(column_name) FROM table_name;

3) MID() - Extract characters from a text field

SELECT MID(column_name,start[,length]) AS some_name FROM table_name;

4) LEN() - Returns the length of a text field

SELECT LEN(column_name) FROM table_name;

5) ROUND() - Rounds a numeric field to the number of decimals specified

SELECT ROUND(column_name,decimals) FROM table_name;

6) NOW() - Returns the current system date and time

SELECT NOW() FROM table_name;

7) FORMAT() - Formats how a field is to be displayed

    SELECT FORMAT(column_name,format) FROM table_name;

You can also define your function they are called procedure.