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MySQL query to count rows with mutual relation using JOIN?
For this, use aggregate function COUNT(*). Let us first create a table −
mysql> create table DemoTable1543 -> ( -> Value1 int, -> Value2 int -> ); Query OK, 0 rows affected (1.36 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable1543 values(57,60); Query OK, 1 row affected (0.52 sec) mysql> insert into DemoTable1543 values(60,68); Query OK, 1 row affected (0.38 sec) mysql> insert into DemoTable1543 values(90,98); Query OK, 1 row affected (0.36 sec) mysql> insert into DemoTable1543 values(98,90); Query OK, 1 row affected (0.20 sec)
Display all records from the table using select statement −
mysql> select * from DemoTable1543;
This will produce the following output −
+--------+--------+ | Value1 | Value2 | +--------+--------+ | 57 | 60 | | 60 | 68 | | 90 | 98 | | 98 | 90 | +--------+--------+ 4 rows in set (0.00 sec)
Here is the query to count rows with mutual relation like the number 90 in both the columns −
mysql> select count(*) from DemoTable1543 tbl1 -> join DemoTable1543 tbl2 -> on tbl1.Value2=tbl2.Value1 -> where tbl1.Value1=90 and tbl2.Value2=90;
This will produce the following output −
+----------+ | count(*) | +----------+ | 1 | +----------+ 1 row in set (0.00 sec)
Updated on: 12-Dec-2019
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