MySQL Select another row if one doesn't exist

Question

I need to select a row from the table with the specific id, but if the row doesn't exist I need to select the first row. is it possible to do it in a single query?

example: I have a table with an id and text fields. and I have 3 rows in the table

id    txt
----------------
1     text1
2     text2
3     text3

I need to select the first row if say SELECT * FROM myTable WHERE id = 4 doesn't exist Else select the row with id 4.

Answer 1

Try this:

SELECT * FROM 
   (SELECT * FROM your_table
      WHERE id = your_id
      LIMIT 1
    UNION
    SELECT * FROM your_table
      LIMIT 1) a
LIMIT 1

The idea is to take first desired row and appending to this very first row, finally taking first one. If desired row does not exists, first one will be selected...