Noob - 2 months ago 13

SQL Question

I need to find all rows in a SQL table where a certain combination does not exist. For example, consider the below table.

`ID Column_1 Column_2`

1. ID1 ABC

2. ID1 XYZ

3. ID1 QWE

4. ID2 XYZ

5. ID2 QWE

6. ID3 XYZ

7. ID3 ABC

8. ID3 QWE

In the above table, I need to return ID2 as there's no (ID2,ABC) combination. I am currently doing a WHILE and IF EXISTS for each ID in the table, but, is there a more efficient way? The volume is large here.

Answer

could be you need a not in and subselect

```
select distinct column_1
from my_table
where column_1 not in (select column_1 from my_table
where column_2 ='ABC');
```