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Select Query to Display Duplicate Values with Max Date
For this, use GROUP BY and HAVING. Let us first create a table −
mysql> create table DemoTable ( StudentName varchar(100), DueDate date ); Query OK, 0 rows affected (0.72 sec)
Example
Insert some records in the table using insert command −
mysql> insert into DemoTable values('John','2019-01-11'); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable values('Chris','2019-02-11'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values('Chris','2019-03-11'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values('John','2019-04-11'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values('Bob','2019-05-11'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('Bob','2019-06-11'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('Robert','2019-07-11'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('Robert','2019-08-11'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('Robert','2019-09-11'); Query OK, 1 row affected (0.15 sec)
Display all records from the table using select statement −
mysql> select *from DemoTable;
Output
+-------------+------------+ | StudentName | DueDate | +-------------+------------+ | John | 2019-01-11 | | Chris | 2019-02-11 | | Chris | 2019-03-11 | | John | 2019-04-11 | | Bob | 2019-05-11 | | Bob | 2019-06-11 | | Robert | 2019-07-11 | | Robert | 2019-08-11 | | Robert | 2019-09-11 | +-------------+------------+ 9 rows in set (0.00 sec)
Following is the query to display duplicate values with maximum date −
mysql> select tbl.StudentName,max(tbl.DueDate) from DemoTable tbl group by tbl.StudentName having count(*) > 1;
Output
+-------------+------------------+ | StudentName | max(tbl.DueDate) | +-------------+------------------+ | John | 2019-04-11 | | Chris | 2019-03-11 | | Bob | 2019-06-11 | | Robert | 2019-09-11 | +-------------+------------------+ 4 rows in set (0.00 sec)
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