Question

I have a MySQL table with three columns, X, Y and Z

|    X      |     Y     |      Z    |
-------------------------------------
|   john    |  patrick  |   active  |
|   john    |  miles    | inactive  |
|  patrick  |  john     |   active  |

I’d like to select the row data, given ‘john’ as the input, corresponding to the pair john-patrick – that is, john and patrick are both in either X or Y (like select * rows from TABLE where X = john or Y = john and where …)

Is it possible? If so, how?

Answer 1

If I understand you correctly, the values need to be in X and Y
(excluding the tuple (‘john’, ‘miles’, ‘inactive’) in the sample).

Then you will need subquerys for this:

select X,Y,Z from TABLE where
  (X = 'john' or Y = 'john') and 
  X in (select Y from TABLE) and
  Y in (select X from TABLE);

EDIT: The first query was wrong, thanks to ypercube (see comments).

Corrected version:

select X,Y,Z from TABLE where
  (X = 'john' or Y = 'john') and 
  X in (select Y from TABLE as subTable WHERE
         TABLE.X = subTable.Y and TABLE.Y = subTable.X) and
  Y in (select X from TABLE as subTable WHERE
         TABLE.X = subTable.Y and TABLE.Y = subTable.X);