[Mysql] How to find duplicated value in table?

If you want to find duplicated value in table when you can not set unique for some column. Use this query.

Query 1. select column1,count(*) as count where my_table group by column1

* column1 is that you select, my_table is that you want to see.

Then you can see count column that you want to know what values are duplicated.

Query 2. select column1,count(*) as count where my_table group by column1 having count > 1

Then you can see all rows just be duplicated.