Question

I have a table that I need a MYSQL Select statement so I can find the corrupt data and manually fix it.

Sample table

TABLE_A
id | type | value1 | value2
 1 |  10  | 123    | 987  
 2 |  10  | 123    | 987
 3 |  10  | 123    | 789
 4 |  20  | 123    | 987
 5 |  20  | 456    | 987
 6 |  30  | 123    | null
 7 |  30  | 123    | null
 8 |  40  | 123    | 987

I need a select statement that will list records that if they have the same “type” and value1 is not the same and/or value2 not the same.

For Example

• ID 1,2,3 – will be displayed because value2 is different in id 3 and they have the same “type”

• ID 4,5 will be displayed because value1 is different and they have the same “type”

• ID 6,7 will NOT be displayed because value1 and value2 are the same for the same “type”

• ID 8 will NOT be displayed because there is only one with this type.

I have been trying to get my head around this for days and need some help. Thanks

Answer 1

SELECT a.id as problem_id
FROM TABLE_A as a JOIN TABLE_A as b
ON a.type = b.type
WHERE a.value1 <> b.value1 OR a.value2 <> b.value2
GROUP BY problem_id;