What is a function in SQL?
A function in SQL is a ready-made command or set of commands that performs a specific action and returns a result.
Functions come in two kinds:
- Built-in, already part of SQL. For example:
COUNT(), counts the number of rows;SUM(), computes a total;NOW(), returns the current time;UPPER(), converts text to uppercase.
- User-defined, created by a developer to reuse logic.
Example
sql
CREATE FUNCTION get_full_name(first_name VARCHAR, last_name VARCHAR)
RETURNS VARCHAR
AS
BEGIN
RETURN CONCAT(first_name, ' ', last_name);
END;You can then call it like this:
sql
SELECT get_full_name('Ivan', 'Petrov');Functions help you avoid repeating the same code and make queries shorter and clearer.
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