我怎么优化这个SQL语句啊？

bjkider

我怎么优化这个SQL语句啊？
版本：MySQL4.0.13
ExamInfo :170000条
PatientInfo: 13000条
PatientInfo：800条

select count(*) as totalCount
from ExamInfo inner join PatientInfo
(on PatientInfo.PatientIntraID =ExamInfo.PatientIntraID)
left join ProcedureStepInfo
(on ExamInfo.ProcedureStepID=ProcedureStepInfo.ProcedureStepID)
where ExamInfo.PreExamScheduleDate <='2004-11-26'
AND ExamInfo.PreExamScheduleDate >;='1900-11-30'
AND ExamInfo.ExamType='CT';

mysql>; explain :
+-------------------+--------+---------------------------+---------+---------+--------------------------+--------+-------------+
| table | type | possible_keys | key | key_len | ref | rows | Extra |
+-------------------+--------+---------------------------+---------+---------+--------------------------+--------+-------------+
| ExamInfo | ALL | Index_PreExamScheduleDate | NULL | NULL | NULL | 175732 | Using where |
| PatientInfo | eq_ref | PRIMARY,PatientIntraID | PRIMARY | 4 | ExamInfo.PatientIntraID | 1 | Using index |
| ProcedureStepInfo | eq_ref | PRIMARY | PRIMARY | 4 | ExamInfo.ProcedureStepID | 1 | Using index |
+-------------------+--------+---------------------------+---------+---------+--------------------------+--------+-------------+
3 rows in set (0.00 sec)


我怎么优化啊? 这句话在我的服务器上执行效率很低啊得 30秒

odin_free

1。首先靠率合理使用索引Using index
2。靠率用临时表现限制 最大的2个表 然后在连接查询