Question

This has been bugging me for some time now, as a newbie I’m not sure what I should exactly look for. After several hours of Googling I wasn’t able to find a satisfying answer.

I have a relatively complex query which I have stripped and simplified to become:

SELECT field_a1,
       field_a2,
       (SELECT Count(*)
        FROM   table_b
        WHERE  field_b1 IN (SELECT field_x1
                            FROM   table_x) AND field_b2 = 1) AS new_field_1,
       (SELECT Count(*)
        FROM   table_c
        WHERE  field_c1 IN (SELECT field_x1
                            FROM   table_x) AND field_c2 = 2) AS new_field_2,
       (SELECT Count(*)
        FROM   table_d
        WHERE  field_d1 IN (SELECT field_x1
                            FROM   table_x) AND field_d2 = 3) AS new_field_3
FROM   table_a
WHERE  field_a1 IN (SELECT field_x1
                    FROM   table_x)

In the original query, I have a about 30 of those new_field_*. Everything seems to work fine and I’m getting some very satisfying results (end results and performance).

My problem is that this query:

SELECT field_x1
FROM   table_x

is repeated a quite large number of times (30 * number of rows returned) and is always used as a set in which the WHERE IN will look for matches.

My question:

Is it possible to execute this small query only once and keep that result and use it repeatedly?

The only two (ridiculous) things I could think of were something like this (imaginary solution):

temp = (SELECT field_x1
        FROM   table_x)
SELECT field_1
FROM   table_1
WHERE  field_1 IN temp

Or executing this query once on the client side (a webserver running PHP) then appending the result to the future queries using something like this:

$IN_Condition = implode(',', $stmt->execute()->fetchAll(PDO::FETCH_NUM));
$sql_query = "SELECT field_1
              FROM   table_1
              WHERE  field_1 IN ($IN_Condition)"

Answer 1

Try to use JOIN clauses, e.g. –

edited:

SELECT
  field_a1,
  COUNT(b.field_b1) new_field_1,
  COUNT(c.field_c1) new_field_2,
  COUNT(d.field_d1) new_field_3
FROM
  table_a a
JOIN table_x x
  ON x.field_x1 = a.field_a1
LEFT JOIN table_b b
  ON b.field_b1 = x.field_x1
LEFT JOIN table_c c
  ON c.field_c1 = x.field_x1
LEFT JOIN table_d d
  ON d.field_d1 = x.field_x1
GROUP BY
  a.field_a1