GBASE南大通用分享
笛卡尔积语法优化
ORACLE原始语法：
select xm.sfzh,xm.xm,ph.phone,ad.address
from ods.ods_connect_list_xm xm,ods.ods_connect_list_address ad,ods.ods_connect_list_phone ph
where xm.sfzh=ad.sfzh(+)
and xm.sfzh=ph.sfzh(+)
and ph.phone='2259261'
group by xm.sfzh,xm.xm,ph.phone,ad.address;
GBase优化语法：
select xm.sfzh,xm.xm,ph.phone,ad.address
from (select distinct sfzh,xm from ods.ods_connect_list_xm) xm
left join (select distinct sfzh,address from ods_connect_list_address) ad on xm.sfzh=ad.sfzh
left join (select distinct sfzh,phone from ods.ods_connect_list_phone where phone='2259261') ph on xm.sfzh=ph.sfzh
group by xm.sfzh,xm.xm,ph.phone,ad.address;
oracle语法：
select
count(case when (NOT EXISTS(SELECT 1 FROM TJK.WAJ04 B WHERE B.WJ005=''AAC009'' AND IY02.AAC009 = B.WJ014) and IY02.AAC009 is not null) then ''1'' else null end) as "83"
from iy02 where ..............
GBase语法：
select
count(case when (t1.WJ014 is null and IY02.AAC009 is not null) then ''1'' else null end) as "83"
from iy02
left join
(select distinct WJ014 from WAJ04 )t1 on IY02.AAC009 = t1.WJ014
where ..............
