Question

I’m trying to count the total number of rows that would have been returned if there was no global LIMIT set. Here’s what my query looks like:

SELECT SQL_CALC_FOUND_ROWS * FROM table1 WHERE [...]
UNION
SELECT * FROM table2 WHERE [...]
UNION
SELECT * FROM table3 WHERE [...]
UNION 
SELECT * FROM table4 WHERE [...]
LIMIT 0,30

Then I immediately follow that with the SELECT FOUND_ROWS() query. It returns a total of 35 rows, but it should return a total of 400 rows. Any idea how I can count the rows WITHOUT using UNION ALL?

Answer 1

Use temporary table for all union selects:

SELECT SQL_CALC_FOUND_ROWS * FROM 
(
  SELECT * FROM table1 WHERE [...]
  UNION
  SELECT * FROM table2 WHERE [...]
  UNION
  SELECT * FROM table3 WHERE [...]
  UNION 
  SELECT * FROM table4 WHERE [...]
)  temp_table
LIMIT 0,30