SQL Functions

SQL Aggregate Functions



SQL aggregate functions return a single value, calculated from values in a column.

Useful aggregate functions:

    AVG() - Returns the average value
    COUNT() - Returns the number of rows
    FIRST() - Returns the first value
    LAST() - Returns the last value
    MAX() - Returns the largest value
    MIN() - Returns the smallest value
    SUM() - Returns the sum

SQL Scalar functions

SQL scalar functions return a single value, based on the input value.

Useful scalar functions:

    UCASE() - Converts a field to upper case
    LCASE() - Converts a field to lower case
    MID() - Extract characters from a text field
    LEN() - Returns the length of a text field
    ROUND() - Rounds a numeric field to the number of decimals specified
    NOW() - Returns the current system date and time
    FORMAT() - Formats how a field is to be displayed

Tip: The aggregate functions and the scalar functions will be explained in details in the next chapters.


The AVG() Function

The AVG() function returns the average value of a numeric column.

SQL AVG() Syntax

SELECT AVG(column_name) FROM table_name