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MySQL query to select a count on two separate conditions?
Use CASE statement for this. Let us first create a table −
mysql> create table DemoTable -> ( -> StudentMarks int, -> isValid tinyint(1) -> ); Query OK, 0 rows affected (0.68 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable values(45,0); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values(78,1); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable values(45,1); Query OK, 1 row affected (0.31 sec) mysql> insert into DemoTable values(78,1); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values(45,0); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values(82,1); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values(62,1); Query OK, 1 row affected (0.14 sec)
Display all records from the table using select statement −
mysql> select *from DemoTable;
Output
+--------------+---------+ | StudentMarks | isValid | +--------------+---------+ | 45 | 0 | | 78 | 1 | | 45 | 1 | | 78 | 1 | | 45 | 0 | | 82 | 1 | | 62 | 1 | +--------------+---------+ 7 rows in set (0.00 sec)
Here is the query to select a count on two separate conditions −
mysql> select StudentMarks, -> sum(case -> when StudentMarks=45 -> then case when isValid = 1 then 1 else 0 end -> else 1 end -> ) AS Freq -> from DemoTable -> group by StudentMarks;
Output
+--------------+------+ | StudentMarks | Freq | +--------------+------+ | 45 | 1 | | 78 | 2 | | 82 | 1 | | 62 | 1 | +--------------+------+ 4 rows in set (0.00 sec)
Updated on: 30-Jul-2019
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