Question

How to query data from table_1 which ID is not available on table_2 that has duplicate ID’s. See example below.

I want to get ID 5 and 6 of Table 1 from Table 2

Table 1
-------------
| ID | Name |
| 1  | a    |
| 2  | b    |
| 3  | c    |
| 4  | d    |
| 5  | e    |
| 6  | f    |
-------------

Table 2
-------------
Table 1 ID  |
| 1         |
| 1         |
| 2         |
| 2         |
| 2         |
| 3         |
| 4         |
-------------

Thanks!

Answer 1

Minus query would be very helpful, see this link: minus query replacement
for your data this would look like this:

SELECT table_1.id FROM table_1 LEFT JOIN table_2 ON table_2.id = table_1.id WHERE table_2.id IS NULL