Need a row count after SELECT statement: what's the optimal SQL approach?

Question

I\'m trying to select a column from a single table (no joins) and I need the count of the number of rows, ideally before I begin retrieving the rows. I have come to two app

Answer 1

Approach 2 will always return a count that matches your result set.

I suggest you link the sub-query to your outer query though, to guarantee that the condition on your count matches the condition on the dataset.

SELECT 
  mt.my_row,
 (SELECT COUNT(mt2.my_row) FROM my_table mt2 WHERE mt2.foo = mt.foo) as cnt
FROM my_table mt
WHERE mt.foo = 'bar';