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处理mysql使用in关键字子查询1317错误
error 1317 mysql query execution interrupted 消息内容：查询执行被中断（数据库直接挂起）
1. 现象：
（1）在php程序中使用子查询语句，导致mysql自动“挂起”，即数据库“卡死”，程序不能正常运行
（2）在mysql命令行执行子查询语句，mysql需要等待较长时间，提示 “ error 1317 mysql query execution interrupted”
2. 处理办法有两种 ：
006_kh表记录数目共计为 24256 条 uzone_2701_kh 表中记录数目共计为 52327条
原始sql语句（子查询）：
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select count(kh_id) from `006_kh` where kh_id in (select khbh from uzone_2701_kh where uzbh ='180' and jgm='27010899')
使用 desc 命令分析，结果如下:
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mysql>
mysql> desc select count(kh_id) from `006_kh` where kh_id in (select khbh from uzone_2701_kh where uzbh ='180' and jgm='27010899') ;
+----+--------------------+---------------+-------+---------------+---------+---------+------+-------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | extra |
+----+--------------------+---------------+-------+---------------+---------+---------+------+-------+--------------------------+
| 1 | primary | 006_kh | index | null | primary | 4 | null | 89394 | using where; using index |
| 2 | dependent subquery | uzone_2701_kh | all | null | null | null | null | 24256 | using where |
+----+--------------------+---------------+-------+---------------+---------+---------+------+-------+--------------------------+
2 rows in set (0.00 sec)
（1） 第一种方式：
sql脚本
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select count(kh_id) from `006_kh` where kh_id in(select khbh from (select khbh from uzone_2701_kh where uzbh ='180' and jgm='27010899') as khid_array)
使用 desc 命令分析，结果如下:
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mysql> desc select count(kh_id) from `006_kh` where kh_id in(select khbh from (select khbh from uzone_2701_kh where uzbh ='180' and jgm='27010899') as khid_array) ;
+----+--------------------+---------------+-------+---------------+---------+---------+------+-------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | extra |
+----+--------------------+---------------+-------+---------------+---------+---------+------+-------+--------------------------+
| 1 | primary | 006_kh | index | null | primary | 4 | null | 96767 | using where; using index |
| 2 | dependent subquery | | all | null | null | null | null | 24099 | using where |
| 3 | derived | uzone_2701_kh | all | null | null | null | null | 24256 | using where |
+----+--------------------+---------------+-------+---------------+---------+---------+------+-------+--------------------------+
3 rows in set (0.02 sec)
（2）第二种方式 ：
sql脚本 ：
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select count(a.kh_id) from 011_kh a inner join uzone_2701_kh b on a.kh_id = b.khbh where b.uzbh ='180' and b.jgm='27010899'
使用 desc 命令分析，结果如下:
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mysql>
mysql> desc select count(a.kh_id) from 011_kh a inner join uzone_2701_kh b on a.kh_id = b.khbh where b.uzbh ='180' and b.jgm='27010899' ;
+----+-------------+-------+--------+---------------+---------+---------+--------------------+-------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | extra |
+----+-------------+-------+--------+---------------+---------+---------+--------------------+-------+-------------+
| 1 | simple | b | all | null | null | null | null | 24256 | using where |
| 1 | simple | a | eq_ref | primary | primary | 4 | dxzs_v2_new.b.khbh | 1 | using index |
+----+-------------+-------+--------+---------------+---------+---------+--------------------+-------+-------------+
2 rows in set (0.00 sec)
个人试验结论：使用join语句的查询不一定总比使用子查询的语句快，根据我自己的试验结果和desc分析结果 来说，还是join语句比较快，效率比较高；因此，当使用in关键字进行子查询，效率低下时，强烈推荐第二种！
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