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MySQL query to find the number of occurrences from two columns?
Use MySQL GROUP_BY to find the number of occurrences from two columns. Let us first create a table −
mysql> create table DemoTable -> ( -> Name1 varchar(20), -> Name2 varchar(20) -> ); Query OK, 0 rows affected (0.61 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable values('John','Adam'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('Chris','David'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('Robert','Mike'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('David','Chris'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values('Mike','Robert'); Query OK, 1 row affected (0.18 sec)
Display all records from the table using select statement −
mysql> select *from DemoTable;
This will produce the following output −
+--------+--------+ | Name1 | Name2 | +--------+--------+ | John | Adam | | Chris | David | | Robert | Mike | | David | Chris | | Mike | Robert | +--------+--------+ 5 rows in set (0.00 sec)
Here is the query to find the number of occurrences from two columns −
mysql> select greatest(Name1,Name2),least(Name1,Name2),count(*) as Occurrences from DemoTable -> group by greatest(Name1,Name2),least(Name1,Name2);
This will produce the following output −
+-----------------------+--------------------+-------------+ | greatest(Name1,Name2) | least(Name1,Name2) | Occurrences | +-----------------------+--------------------+-------------+ | John | Adam | 1 | | David | Chris | 2 | | Robert | Mike | 2 | +-----------------------+--------------------+-------------+ 3 rows in set (0.02 sec)
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