mysql. Query to select non-intersecting values ​​of two columns?

Question

MySQL

There are data of two columns
cid fid
+-----+-----+
| 24 | 12 |
+-----+-----+
| 24 | 19 |
+-----+-----+
| 25 | 19 |
+-----+-----+
| 24 | 12 |
+-----+-----+
| 25 | 12 |
+-----+-----+
You need to get the following result
+-----+-----+
| 24 | 12 |
+-----+-----+
| 24 | 19 |
+-----+-----+
| 25 | 19 |
+-----+-----+
| 25 | 12 |
+-----+-----+

Answer 1

SELECT DISTINCT( f2 ), f1 FROM t;