I need an update query with a WHERE statement, but if the record does not exist it should insert the data.

e.g. `UPDATE table SET this = 'that', that = 'this' WHERE this = 'this' AND that = 'that'`

I don't have an unique value, I have 2 columns that can't occur 2 times or more. Let me give you an example:

I've got a table:

```
Column1 | Column2 | Column3
---------------------------
1       | 2       | 500
1       | 3       | 500 This is OK because column2 is other than above
2       | 2       | 500 ALSO OK because column1 is other than above!
1       | 2       | 500 NOT OK! Already exists -> need update for Column3! needs to be 1000 now!

```

As you can see in the table, the two columns can occur more than once!

Is there a function for this? Or should I first check if there is a record? I do not have an `Unique key`, so I can't use [this](https://stackoverflow.com/questions/15383852/sql-if-exists-update-else-insert-into).