SQL Functions

SQL has many built-in functions for counting and calculation.

SQL Aggregate Functions

SQL Aggregate functions calculate values from columns and return a single value.

Useful Aggregate functions:

• AVG() - Returns the average value
• COUNT() - Returns the number of rows
• FIRST() - Returns the value of the first record
• LAST() - Returns the value of the last record
• MAX() - Returns the maximum value
• MIN() - Returns the minimum value
• SUM() - Returns the sum

SQL Scalar Functions

SQL Scalar functions based on input values return a single value.

Useful Scalar functions:

• UCASE() - Converts a field to uppercase
• LCASE() - Converts a field to lowercase
• MID() - Extracts characters from a text field, used in MySQL
• SubString(field, 1, end) - Extracts characters from a text field
• LEN() - Returns the length of a text field
• ROUND() - Rounds a numeric field to the specified number of decimal places
• NOW() - Returns the current system date and time
• FORMAT() - Formats the display of a field

Tip:In the following chapters, we will discuss Aggregate and Scalar functions in detail.