[英]Optimize SQL Query
我在MySQL DB上有以下查詢:
SELECT * , r.id, x.real_name AS u_real_name, u.real_name AS v_real_name, y.real_name AS v_real_name2
FROM url_urlaube r
LEFT JOIN g_users u ON ( r.v_id = u.id )
LEFT JOIN g_users x ON ( r.u_id = x.id )
LEFT JOIN g_users y ON ( r.v_id2 = y.id )
WHERE (
(
FROM_UNIXTIME( 1283205600 ) >= r.from
AND FROM_UNIXTIME( 1283205600 ) <= r.to
)
OR (
FROM_UNIXTIME( 1280613600 ) >= r.from
AND FROM_UNIXTIME( 1280613600 ) <= r.to
)
OR (
FROM_UNIXTIME( 1280613600 ) < r.from
AND FROM_UNIXTIME( 1283205600 ) > r.to
)
)
ORDER BY r.from ASC
我試圖通過在(r.from,r.to)上添加索引來優化此查詢,但是我沒有工作。
當我讓我解釋這個查詢時,它說:
+----+-------------+-------+--------+---------------+---------+---------+-------------+------+-----------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+--------+---------------+---------+---------+-------------+------+-----------------------------+
| 1 | SIMPLE | r | ALL | from | NULL | NULL | NULL | 42 | Using where; Using filesort |
| 1 | SIMPLE | u | eq_ref | PRIMARY | PRIMARY | 4 | res.r.v_id | 1 | |
| 1 | SIMPLE | x | eq_ref | PRIMARY | PRIMARY | 4 | res.r.u_id | 1 | |
| 1 | SIMPLE | y | eq_ref | PRIMARY | PRIMARY | 4 | res.r.v_id2 | 1 | |
+----+-------------+-------+--------+---------------+---------+---------+-------------+------+-----------------------------+
4 rows in set (0.00 sec)
為什么?
謝謝你的幫助。
復合索引在這里無濟於事,因為您的條件具有不同的比較功能。 嘗試在r.from和r.to上添加單獨的索引。 實際上,我認為r.from上的一個索引就足夠了。
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