那些臭名昭著的sql

* from a, b left join c on b.id = c.id left join d on c.id = d.id

• 多表关联查询，where条件使用各种函数，导致索引无效。数据量如果打起来以后会导致查询像蜗牛一样。

select 
trim(d.circuitid) as circuitid,
trim(d.Code) as Code,
trim(d.Oldname) as Oldname,
trim(d.Circuittype) as Circuittype,
trim(d.Status) as Status,
trim(d.customerid) as acustomerid,
trim(d.alinkman) as alinkman,
trim(d.zlinkman) as zlinkman,
trim(d.alinkmantel) as alinkmantel,
trim(d.zlinkmantel) as zlinkmantel,
trim(d.busi_no) as busi_no,
trim(d.service_serial) as service_serial,
trim(a.region_ID) as regionid ,
2 as SORTID
from test1 a,test2 b,test3 c,test4 d 
where trim(a.room_id)=trim(b.roomID) and trim(b.neid)=trim(c.neid) and (trim(c.portid)=trim(d.aendname) or trim(c.portid)=trim(d.zendname))

 

那些臭名昭著的sql

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