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Count duplicate ids and display the result in a separate column with MySQL
Let us first create a table −
mysql> create table DemoTable1453 -> ( -> CustomerId int, -> CustomerReviewNumber int -> ); Query OK, 0 rows affected (0.58 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable1453 values(10,4); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable1453 values(10,4); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable1453 values(11,5); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1453 values(11,5); Query OK, 1 row affected (0.07 sec) mysql> insert into DemoTable1453 values(11,5); Query OK, 1 row affected (0.06 sec) mysql> insert into DemoTable1453 values(13,2); Query OK, 1 row affected (0.27 sec) mysql> insert into DemoTable1453 values(11,5); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1453 values(10,4); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1453 values(13,2); Query OK, 1 row affected (0.14 sec)
Display all records from the table using select statement −
mysql> select * from DemoTable1453;
This will produce the following output −
+------------+----------------------+ | CustomerId | CustomerReviewNumber | +------------+----------------------+ | 10 | 4 | | 10 | 4 | | 11 | 5 | | 11 | 5 | | 11 | 5 | | 13 | 2 | | 11 | 5 | | 10 | 4 | | 13 | 2 | +------------+----------------------+ 9 rows in set (0.00 sec)
Following is the query to count duplicate ids −
mysql> select CustomerId,count(distinct CustomerReviewNumber) -> from DemoTable1453 -> group by CustomerId;
This will produce the following output −
+------------+--------------------------------------+ | CustomerId | count(distinct CustomerReviewNumber) | +------------+--------------------------------------+ | 10 | 1 | | 11 | 1 | | 13 | 1 | +------------+--------------------------------------+ 3 rows in set (0.14 sec)
Updated on: 10-Dec-2019
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