I already showed the value of minimizing a test case in Single Server Example, where I reduced an incorrect SELECT to a CREATE TABLE that reproduced the wrong parameters. Here I will discuss the principle of a minimal test case in more general terms.

As an example, take the following huge query^[22]:

SELECT
IF(TABLE1.FIELD1 = 'R' AND TABLE1.FIELD2 IS NOT NULL AND TABLE1.FIELD3 = '1' AND
TABLE2.FIELD4 = TABLE2.FIELD5 AND TABLE3.FIELD6 = TABLE4.FIELD6, TABLE3.FIELD7,
TABLE4.FIELD7) AS ALIAS1,

IF(TABLE1.FIELD1 = 'R' AND TABLE1.FIELD2 IS NOT NULL AND TABLE1.FIELD3 = '1' AND
TABLE2.FIELD4 = TABLE2.FIELD5 AND TABLE3.FIELD6 = TABLE4.FIELD6, TABLE3.FIELD8,
TABLE4.FIELD8) AS ALIAS2,

SUM(
IF (
(SELECT TABLE5.FIELD7 FROM TABLE4 ALIAS3, TABLE2 ALIAS4, TABLE4 ALIAS5 WHERE
TABLE5.FIELD5 = ALIAS4.FIELD4 AND ALIAS4.FIELD5 = ALIAS5.FIELD5 AND
ALIAS5.FIELD7 = FIELD9 AND TABLE5.FIELD6 = TABLE6.FIELD7 LIMIT 1 ) IS NULL, 0,
TABLE7.FIELD10/TABLE7.FIELD11)
) AS ALIAS11

FROM TABLE4 ,TABLE4 ALIAS6, TABLE8 , TABLE4 ALIAS7, TABLE9 , TABLE7 , TABLE2 ,
TABLE1 F....