The MySQL count() function is used to return the count of an expression. It is used when you need to count some records of your table.
SELECT COUNT (aggregate_expression) FROM table_name [WHERE conditions];
aggregate_expression: It specifies the column or expression whose NON-NULL values will be counted.
table_name: It specifies the tables, from where you want to retrieve records. There must be at least one table listed in the FROM clause.
WHERE conditions: It is optional. It specifies the conditions that must be fulfilled for the records to be selected.
Consider a table named "officers", having the following data.
Execute the following query:
SELECT COUNT(officer_name) FROM officers;
Here, you can see that that the COUNT function calculates the total number of officers in the table.