联合索引建立依据

区分度高的放在前面

select count(distinct  destinationmachine) cdd, count(distinct  factoryname) cdf, count(distinct requesttype) cdr, count(distinct  CASSETTETYPE) cdc, count(distinct state) cds from dsptransfercommand;

CDD         CDF         CDR            CDC            CDS

----------  ---------   ----------     ----------     ----------

259          4           4              2              8    

 

Select count(*) from dsptransfercommand表计算总数

 

选择索引选择性好的列放在前面。