Question

mssql 语句 优化

rs.open "select *,(select sh from [gy_list] where dd_id=[dd_list].id) as sh,(select sh_time from [gy_list] where dd_id=[dd_list].id) as sh_time,(select sh_name from [gy_list] where dd_id=[dd_list].id) as sh_name from [dd_list] "&ss&" order by id desc",conn,1,1

rs1.open "select scdw from [scjh] where dd_id="&rs("id")&"",conn,1,1
do while not rs1.eof
scdw=scdw&" "&rs1("scdw")&""
rs1.movenext
loop
rs1.close

rs.close

Answer 1

select *,(select sh from [gy_list] where dd_id=[dd_list].id) as sh,
(select sh_time from [gy_list] where dd_id=[dd_list].id) as sh_time,
(select sh_name from [gy_list] where dd_id=[dd_list].id) as sh_name
from [dd_list]
order by id desc
--等价于下面,把A.*换成你具体需要的列字段,SELECT * ..要尽量不用
SELECT A.*,B.sh,B.sh_time,B.sh_name
FROM [dd_list] A,[gy_list] B
WHERE A.ID=B.dd_id

Answer 2

不要用select * ,而是指定具体的列名
对字符型列使用 RTRIM() 清除多余的空格.
子查询并不比内联接快！

Answer 3

....