EXPLAIN SELECT * FROM `T_UserBase` AS users
LEFT OUTER JOIN `T_ScheduledTestTakerUsers` AS takers ON takers.`F_UserID` = users.`F_UserID`
LEFT OUTER JOIN `T_ScheduledTestsBase` AS tests ON tests.`F_TestID` = takers.`F_TestID`
LEFT OUTER JOIN `T_SessionTrack` AS sessions ON sessions.`F_UserID` = users.`F_UserID`
WHERE (tests.`F_TestID` = 4510) OR (sessions.`F_ContentID` = 4510)
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE users NULL ALL NULL NULL NULL NULL 562826 100.00 NULL
1 SIMPLE takers NULL ref T_ScheduledTestTakerUsers_F_UserID_index T_ScheduledTestTakerUsers_F_UserID_index 4 rack80829.users.F_UserID 1 100.00 Using index
1 SIMPLE tests NULL eq_ref PRIMARY PRIMARY 4 rack80829.takers.F_TestID 1 100.00 NULL
1 SIMPLE sessions NULL ref Index_1 Index_1 4 rack80829.users.F_UserID 1 100.00 Using where
