In SQL, an aggregate function is a function that performs a calculation on multiple values and returns a single value. These functions are used to summarize data from multiple rows into a single value. Some common aggregate functions in SQL include:
- COUNT: Counts the number of rows in a particular column.
- SUM: Adds together all the values in a particular column.
- AVG: Calculates the average of a group of selected values.
- MIN: Returns the lowest value in a particular column.
- MAX: Returns the highest value in a particular column.
Aggregate functions are often used in conjunction with the GROUP BY clause, which is used to group rows based on a specific column. The syntax for an aggregate function in SQL is as follows:
SELECT aggregate_function(column_name) FROM table_name [WHERE condition];
It is important to note that aggregate functions ignore null values, except for COUNT(*).
