以下SQL查询大约需要 1分钟。直接输入SQL控制台时执行15秒。 qv_attribute表中有 6636条记录。
此查询的执行时间是否正常？有没有办法通过更改数据库设置或优化查询来减少运行此操作所需的时间？
SELECT a.node_id,
MAX(CASE WHEN(b.att_id = 9003) THEN a.att_description END) AS 'ICS_Owner',
MAX(CASE WHEN(b.att_id = 9004) THEN a.att_description END) AS 'Service',
MAX(CASE WHEN(t.rel_id = 12092) THEN t.att_description END) AS 'Contact_Name',
MAX(CASE WHEN(t.rel_id = 12610) THEN t.att_description END) AS 'Address_1',
MAX(CASE WHEN(t.rel_id = 9007) THEN t.att_description END) AS 'Address_2',
MAX(CASE WHEN(t.rel_id = 12612) THEN t.att_description END) AS 'City',
MAX(CASE WHEN(t.rel_id = 12614) THEN t.att_description END) AS 'State',
MAX(CASE WHEN(t.rel_id = 13508) THEN t.att_description END) AS 'a',
MAX(CASE WHEN(t.rel_id = 13509) THEN t.att_description END) AS 'b',
MAX(CASE WHEN(b.att_id = 13132) THEN a.att_description END) AS 'Description',
MAX(CASE WHEN(des.node_id = 10824) THEN des.att_description END) AS 'Row_Description'
FROM `qv_attribute` t, `qv_attribute` a, `qv_attribute` b, `qv_attribute` des
WHERE b.att_id IN (9003,9004,13132,14542)
AND b.att_name = a.att_name
AND ((a.node_id = 1554 AND
((t.node_id = 1776 AND des.att_order = 1)
OR (t.node_id = 1780 AND des.att_order = 2)
OR (t.node_id = 1781 AND des.att_order = 3)
OR (t.node_id = 1782 AND des.att_order = 4)
OR (t.node_id = 1783 AND des.att_order = 5)
OR (t.node_id = 1784 AND des.att_order = 6)
OR (t.node_id = 1778 AND des.att_order = 7)
OR (t.node_id = 1777 AND des.att_order = 8)))
OR (a.node_id = 1574 AND
((t.node_id = 1574 AND des.att_order = 1)
OR (t.node_id = 1779 AND des.att_order = 2)
OR (t.node_id = 1576 AND des.att_order = 3)
OR (t.node_id = 1577 AND des.att_order = 4)
OR (t.node_id = 1710 AND des.att_order = 5)
OR (t.node_id = 1711 AND des.att_order = 6)
OR (t.node_id = 1712 AND des.att_order = 7)))
OR (a.node_id = 1803 AND
((t.node_id = 1838 AND des.att_order = 1)
OR (t.node_id = 1839 AND des.att_order = 2)
OR (t.node_id = 1840 AND des.att_order = 3)
OR (t.node_id = 1805 AND des.att_order = 4)))
OR (a.node_id = 1831 AND
((t.node_id = 1842 AND des.att_order = 1)
OR (t.node_id = 1847 AND des.att_order = 2)
OR (t.node_id = 1833 AND des.att_order = 3)
OR (t.node_id = 1848 AND des.att_order = 4)
OR (t.node_id = 1845 AND des.att_order = 5)
OR (t.node_id = 1846 AND des.att_order = 6)
OR (t.node_id = 1841 AND des.att_order = 7)
OR (t.node_id = 1844 AND des.att_order = 8)
OR (t.node_id = 1843 AND des.att_order = 9)))
OR (a.node_id = 1810 AND
((t.node_id = 1854 AND des.att_order = 1)
OR (t.node_id = 1849 AND des.att_order = 2)
OR (t.node_id = 1851 AND des.att_order = 3)
OR (t.node_id = 1853 AND des.att_order = 4)
OR (t.node_id = 1852 AND des.att_order = 5)
OR (t.node_id = 1812 AND des.att_order = 6)
OR (t.node_id = 1850 AND des.att_order = 7))))
GROUP BY a.node_id, t.node_id
EXPLAIN EXTENDED：
+----+-------------+-------+-------+---------------+---------+---------+------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+-------+---------------+---------+---------+------+------+----------------------------------------------+
| 1 | SIMPLE | b | range | PRIMARY | PRIMARY | 4 | NULL | 4 | Using where; Using temporary; Using filesort |
| 1 | SIMPLE | des | ALL | NULL | NULL | NULL | NULL | 6695 | Using where |
| 1 | SIMPLE | t | range | node_id | node_id | 4 | NULL | 629 | Using where |
| 1 | SIMPLE | a | range | node_id | node_id | 4 | NULL | 139 | Using where |
+----+-------------+-------+-------+---------------+---------+---------+------+------+----------------------------------------------+
4 rows in set, 1 warning (0.00 sec)
答案 0 :(得分：2)
想想如果你创建了一个如下所示的表格，你可以做的魔法：
a_node_id t_node_id att_order
1554 1776 1
1554 1780 2
1554 1781 3
1554 1782 4
1554 1783 5
1554 1784 6
1554 1778 7
1554 1777 8
1574 1574 1
1574 1779 2
1574 1576 3
1574 1577 4
1574 1710 5
1574 1711 6
1574 1712 7
1803 1838 1
1803 1839 2
1803 1840 3
1803 1805 4
etc
附加提示：将它放在一个表中并保持连接到该表 - 比你当前拥有的where子句快得多。
答案 1 :(得分：2)
我认为问题在于你没有为t或des指定任何连接条件，而是对它们进行了大量的比较。所以你要用t和des的每个组合重复a和b的每个匹配，这可能不是你想要的。
结果表的行数等于（a join b）* t * des
以下是你的where子句可以归结为：
AND ((a.node_id = 1554 AND
((t.node_id IN 1776, 1780, 1781, 1782, 1784, 1778, 1777) AND des.att_order BETWEEN 1 AND 8)
OR (a.node_id = 1574 AND
((t.node_id IN 1779, 1576, 1577, 1710, 1711, 1712) AND des.att_order BETWEEN 1 AND 7)
...
那个查询非常难看，但是在大约7k行时，带有一堆过滤器的枢轴不应该花费一分钟
答案 2 :(得分：0)
假设您已经为自己的表编入索引 - 减速来自您的CASE WHEN组合。将其拆分为11个单独的查询，您将观察到加速。
另外，如果你必须在1分钟过长的情况下经常运行这个查询 - 你可能想要重新设计数据库结构以保留一些冗余但快速查询的信息。
祝你好运！