SQL COUNT()
The COUNT() function returns the number of rows matching the specified criteria.
SQL COUNT(column_name) Syntax
COUNT(column_name) function returns the number of values in the specified column (NULL is not counted):
SQL COUNT(*) Syntax
COUNT(*) function returns the number of records in the table:
SQL COUNT(DISTINCT column_name) Syntax
COUNT(DISTINCT column_name) The function returns the number of distinct values for the specified column:
Note: COUNT(DISTINCT) works with ORACLE and Microsoft SQL Server, but cannot be used with Microsoft Access.
Demo Database
In this tutorial, we will use the php sample database.
The following is the data selected from the "access_log" table:
| aid | site_id | count | date |
+-----+---------+---- ---+------------+
| 1 | 1 | 45 | 2016-05-10 |
| 2 | 3 | 100 | 2016-05-13 |
| 3 | 1 | 230 | 2016-05-14 |
| 4 | 2 | 10 | 2016-05-14 |
| 5 | 5 | 205 | 2016-05-14 |
| 6 | 4 | 13 | 2016-05-15 |
| 7 | 3 | 220 | 2016-05-15 |
| 8 | 5 | 545 | 2016-05-16 |
| 9 | 3 | 201 | 2016-05-17 |
+-----+---------+-------+---------- -+
SQL COUNT(column_name) Example
The following SQL statement calculates the total number of visits to "site_id"=3 in the "access_log" table:
Example
WHERE site_id=3;
SQL COUNT(*) Example
The following SQL statement calculates the total number of records in the "access_log" table:
Example
Execute the above SQL and the output result is as follows:
##SQL COUNT(DISTINCT column_name ) ExampleThe following SQL statement counts the number of records with different site_ids in the "access_log" table:
