select Code, CodeName, CodeAlias, ComCode, OtherSign
from ldcode
where codetype = ‘edorapptype‘
and code <> (case
when (select 1
from lccont b
where b.contno = ‘W86190001290019‘
and b.trdingchannel like ‘ZFB%‘) = 1 then
‘-9‘
else
‘9‘
end)
and othersign = ‘1‘
order by length(code), code asc
去掉(case when)
select Code, CodeName, CodeAlias, ComCode, OtherSign from ldcode where codetype = ‘edorapptype‘ and code <> ‘-9‘ and othersign = ‘1‘
分析case when 1= 1 then ‘-9‘ else ‘9‘ end
(case
when (select 1
from lccont b
where b.contno = ‘W86190001290019‘
and b.trdingchannel like ‘ZFB%‘) = 1 then
‘-9‘
else
‘9‘
end)
分析 select 1
select 1 from lccont b
where b.contno = ‘W86190001290019‘
and b.trdingchannel like ‘ZFB%‘
select * ,select 某字段,
可以用来查询表中是否有符合条件的记录(比如select 1 from seckill where id = 1001;)，select 1一般用来当作条件使用，比如exists( select 1 from 表名)等。select 1的效率比select 列名和select*快，因为不用查字典表。
原文：https://www.cnblogs.com/zytcomeon/p/13964742.html