求最效率的SQL查询语句写法 SQL2000表1:A
字段:ID NAME DATE TEMPID表2: B
字段:ID NAME DATE TEMPID用一条语句查询:
求表A和B中 DATE符合当天日期,NAME符合“张三” ,TEMPID最大的那条记录因为数据量大,所以希望求效率的写法
字段:ID NAME DATE TEMPID表2: B
字段:ID NAME DATE TEMPID用一条语句查询:
求表A和B中 DATE符合当天日期,NAME符合“张三” ,TEMPID最大的那条记录因为数据量大,所以希望求效率的写法
select Max(MaxTEMPID) From
(
select Max(TEMPID) as MaxTEMPID from A where NAME ='张三' and DATE=[参数传]
union
select Max(TEMPID) as MaxTEMPID from B where NAME ='张三' and DATE=[参数传]
)
和
NAME
加索引
(
select Max(TEMPID) as MaxTEMPID from A where NAME ='张三' and DATE=[参数传]
union
select Max(TEMPID) as MaxTEMPID from B where NAME ='张三' and DATE=[参数传]
)as tmptabsorry
select Max(MaxTEMPID) as id From
(
select Max(ID) as MaxTEMPID from Table_1 where NAME ='张三' and DATE=''
union
select Max(ID) as MaxTEMPID from Table_2 where NAME ='张三' and DATE=''
) as t
不可能有问题,我这里ok
select top1 * from A where name where NAME ='张三' and DATE='...' order by TEMPID DESC
union
select top1 * from B where name where NAME ='张三' and DATE='...' order by TEMPID DESC