Functions in SQL are predefined procedures that take input values, perform an operation, and return a single value or a set of values. SQL functions are used to manipulate and retrieve data from databases. There are many built-in functions in SQL, including aggregate functions, string functions, date and time functions, and mathematical functions.
Aggregate functions are used to perform calculations on a set of values and return a single value. Examples of aggregate functions include COUNT, SUM, AVG, MIN, and MAX.
String functions are used to manipulate strings of text. Examples of string functions include CONCAT, SUBSTRING, and UPPER.
Date and time functions are used to manipulate date and time data. Examples of date and time functions include CURRENT_DATE, CURRENT_TIME, and DATEADD.
Mathematical functions are used to perform mathematical calculations. Examples of mathematical functions include ABS, CEILING, FLOOR, and ROUND.
Functions in SQL are generally used in SELECT statements to retrieve data from a database. For example, the following SQL statement uses the SUM function to calculate the total sales for a given year:
SELECT SUM(sales_amount)
FROM sales
WHERE sales_year = '2022';
In addition to built-in functions, SQL also allows users to create their own user-defined functions. These functions can be used to perform custom calculations or manipulate data in a specific way.
Overall, functions in SQL provide a powerful tool for manipulating and retrieving data from databases. They allow for complex calculations to be performed quickly and easily, and can help simplify SQL queries.
