I have the following problem, i have 2 tables:
Table A (with the columns "ColumnA" and "ColumnB")
| ColumnA | ColumnB |
|---|---|
| 111 | 555 |
| 111 | 333 |
| 111 | 444 |
| 222 | 555 |
| 222 | 666 |
Table B (with the columns "ColumnC" and "ColumnD")
| ColumnC | ColumnD |
|---|---|
| 111 | 222 |
| 111 | 333 |
| 111 | 444 |
| 222 | 444 |
i want to insert the values of table B into table A, as long as a combination of both values is not yet in table A (by joining ColumnA/ColumnC and ColumnB/ColumnD). I know how to work with a left join (and the where column... is null) to add values for one column that is not yet available but i don't know how to do it with two columns (as a combination of two columns).
In other words in my case only these two would be added because the combination of those two is not yet available in table A (i hope it's clear what i mean):
| 111 | 222 |
| 222 | 444 |
Tried it with a left join and where column is null clause but couldn't make it work for two columns.
This is what i have so far:
select * from TableA
left join TableB on TableA.ColumnB = TableB.ColumnD
and TableB.ColumnA = TableA.ColumnC
where ...