sql小结
（案例来自医药采购）
1.1 内链接关联查询：（一对一：只能查询到一条数据）
如果表A和表B有一个外键关联 （由于有外键可以通过内链接），可以通过外键进行内链接查询
select dictinfo.*,dicttype.typename
from dictinfo, dicttype
where dictinfo.typecode = dicttype.typecode
--不通过外键，通过groupid查询用户类型的代码结果集，只能查询出一条记录，可以使用内链接
selectsysuser.*, dictinfo.info
from sysuser,
(select dictcode, typecode, info from dictinfo where typecode = 's01') dictinfo
where sysuser.groupid = dictinfo.dictcode
小结：如果主查询表字段从关联表只查询出一条记录，这个字段就可以作为内链接关联字段
--内链接的错误的例子，通过关联查询出重复记录
--使用groupid从select dictcode, typecode, info fromdictinfo可以找到多个记录，不能使用内链接，可能会出现重复记录
selectsysuser.*
from sysuser, (select dictcode, typecode, info from dictinfo) dictinfo
where sysuser.groupid = dictinfo.dictcode
注意：如果使用内链接查询出现重复记录，首先去思考是否是sql写错了，不能直接去使用distinct去除重复记录。
有一些特殊情况下还是需要使用distinct去除重复记录，比如复杂的统计分析sql。
1.2 外链接关联查询：
表A，表B中只有一部分数据和表A匹配，不能使用内链接。
主查询是表A，只能使用外链接。
--查询用户所属单位,sysid对应三张表的id
左外链接 left 左边的为主查询表全部显示 右边为关联查询表（部分字段） on 后边为要关联的字段
selectsysuser.*,useryy.mc from sysuser leftjoin useryy on sysuser.sysid =useryy.id
右外链接right右边主查询表全部显示左边为关联查询表（部分字段） on后边为要关联的字段
select * from useryy rightjoin sysuser on sysuser.sysid =useryy.id
--以上的需要不能使用内链接
selectsysuser.*,useryy.mc from sysuser,useryy where sysuser.sysid = useryy.id
小结：
表A中从表B中只能关联查询一部分数据，只能使用外链接
1.3 子查询
selectsysuser.*,
(select * from useryywhereid = sysuser.sysid)
from sysuser
子查询只能返回一列，否则：报错
子查询只允许返回一行，否则：
正确的sql:
--子查询
--根据sysid取出单位名称
--根据groupid查询用户类型代码对应的名称
selectsysuser.*,
(select mcfrom useryy whereid =sysuser.sysid)sysmc,
(select info from dictinfo where dictcode = sysuser.groupid and typecode = 's01')groupname
from sysuser
1.4 嵌套表
可以将一个sql查询结果组成一个虚表，查询方式和查询一个实体表相同的。
组成的虚拟表字段是不允许重复的，否则 ：
2 notin 关键字
select
ypxx.id,
ypxx.bm,
ypxx.mc,
ypxx.jx,
ypxx.gg,
ypxx.zhxs,
ypxx.scqymc,
ypxx.spmc,
ypxx.zbjg,
ypxx.jyzt,
(select info
from dictinfo
where ypxx.jyzt = dictcode
and typecode = '003') jyztmc
from ypxx
-- notin 将供货商药品目录已经存在药品过虑掉not后括号里的查询结果过滤掉
--ypxx表中记录，根据ypxxid关联，不在select ypxxid from gysypml whereusergysid='5197cdd2-08cf-11e3-8a4f-60a44cea4388'结果集中
where ypxx.id notin(
--某个供货商药品目录结果集
select ypxxid from gysypml where usergysid='5197cdd2-08cf-11e3-8a4f-60a44cea4388'
)
3 not exists 关键字
--
select ypxx.id,
ypxx.bm,
ypxx.mc,
ypxx.jx,
ypxx.gg,
ypxx.zhxs,
ypxx.scqymc,
ypxx.spmc,
ypxx.zbjg,
ypxx.jyzt,
(select info
from dictinfo
where ypxx.jyzt = dictcode
and typecode = '003') jyztmc
--子查询，关联查询到说明此药品id在供货商药品目录存在
--(select id from gysypml whereusergysid='5197cdd2-08cf-11e3-8a4f-60a44cea4388' and ypxx.id = gysypml.ypxxid)gysypmlid
from ypxx
--查询子查询不为空的值
wherenotexists (selectid
from gysypml
where usergysid = '5197cdd2-08cf-11e3-8a4f-60a44cea4388'
and ypxx.id = gysypml.ypxxid)
--每个记录查询时，都需要执行exists中的子查询
--建议子查询条件根据主键或索引查询，可以提高效率，推荐使用exists，因为exists比in或not in速度要高
4 in 关键字
select
gysypml.id gysypmlid,
gysypml.ypxxid,
gysypml.usergysid,
usergys.mc usergysmc,
gysypml_control.control,
(select info
from dictinfo
where typecode = '008'
and dictcode = gysypml_control.control)controlmc,
ypxx.id,
ypxx.bm,
ypxx.mc,
ypxx.jx,
ypxx.gg,
ypxx.zhxs,
ypxx.scqymc,
ypxx.spmc,
ypxx.zbjg,
ypxx.jyzt,
(select info
from dictinfo
where ypxx.jyzt = dictcode
and typecode = '003') jyztmc
from gysypml, usergys, gysypml_control,ypxx
where gysypml.usergysid = usergys.id
and gysypml.ypxxid =gysypml_control.ypxxid
and gysypml.usergysid =gysypml_control.usergysid
and gysypml.ypxxid = ypxx.id
--限制只查询医院本区域供货商的药品目录
--1.1.16.是医院所在区域
and gysypml.usergysid in (
select usergysarea.usergysid from usergysarea where'1.1.16.'like usergysarea.areaid|| '%'
)
--将采购单中药品过虑掉
--2014101040就是采购单id
and gysypml.ypxxid notin(
select yycgdmx.ypxxid from yycgdmx2014 yycgdmxwhere yycgdmx.yycgdid = '2014101040'
)
--分析所需要的子查询
--采购单下药品id列表
select yycgdmx.ypxxid from yycgdmx2014 yycgdmx where yycgdmx.yycgdid ='2014101040'
--查询出医院所在区域供货商的信息
select usergysarea.usergysid from usergysarea where '1.1.16.' likeusergysarea.areaid || '%'
--查询医院的区域(三级区域1.1.16.)
select dq from useryy where id='1f8b098b-067e-11e3-8a3c-0019d2ce5116'
5 sum 关键字
sum 求和 ，nvl 如果 该字段为空则按0 计算
select sum(nvl(yycgdmx.cgl,0)) cgl,
sum(nvl(yycgdmx.cgje,0)) cgje
from yycgdmx2015 yycgdmx,
yycgd2015 yycgd, useryy,
ypxx, usergys
where yycgdmx.yycgdid
= yycgd.id
and yycgd.useryyid = useryy.id
and yycgdmx.ypxxid = ypxx.id
and yycgdmx.usergysid = usergys.id
6 groupby 关键字
groupby 按照什么统计
group by business.id,business.bm,business.mc 先按照id 统计
如果business.bm列有重复按照business.bm统计
如果business.mc列有重复然后按照business.mc统计
select
business.id,
business.bm,
business.mc,
sum(nvl(business.cgl,0))cgl,
sum(nvl(business.cgje,0))cgje,
sum(nvl(business.rkl,0))rkl,
sum(nvl(business.rkje,0))rkje,
sum(nvl(business.thl,0))thl,
sum(nvl(business.thje,0))thje,
sum(nvl(business.jsl,0))jsl,
sum(nvl(business.jsje,0))jsje
from (
selectuseryy.id useryyid,
useryy.mc useryymc,
yycgd.bm yycgdbm,
yycgd.id yycgdid,
usergys.id usergysid,
usergys.mc usergysmc,
yycgdmx.ypxxid,
ypxx.id,
ypxx.bm,
ypxx.mc,
ypxx.jx,
ypxx.gg,
ypxx.zhxs,
ypxx.scqymc,
ypxx.spmc,
ypxx.jyzt,
(select info
from dictinfo
where ypxx.jyzt = dictcode
and typecode = '003') jyztmc,
(select info
from dictinfo
where typecode = '011'
and dictcode = yycgdmx.cgzt) cgztmc,
yycgdmx.cgl,
yycgdmx.cgje,
yycgdmx.rkl,
yycgdmx.rkje,
yycgdmx.thl,
yycgdmx.thje,
yycgdmx.jsl,
yycgdmx.jsje
from yybusiness2014 yycgdmx, yycgd2014yycgd, useryy, usergys, ypxx
where yycgdmx.yycgdid = yycgd.id
and yycgd.useryyid = useryy.id
and yycgdmx.usergysid = usergys.id
and yycgdmx.ypxxid = ypxx.id
--监管单位查询管理地区内医院采购明细信息
and useryy.id in (
--管理地区内医院
selectidfrom useryy where dq like'1.1.%')
--医院查询自己的采购明细信息
and useryy.id = '1f8b098b-067e-11e3-8a3c-0019d2ce5116'
--供货商查询：与本供货商相关的采购明细信息
and usergys.id = '5197cdd2-08cf-11e3-8a4f-60a44cea4388'
)business
--分类统计
--按药品统计
groupbybusiness.id,business.bm,business.mc
7 实现（用例）
查询出所有镇区域内的采购金额没有采购的以0 计算
select areainfo.areaname,
nvl(yybusiness.cgje,0)cgje
from (select areaname, 0 cgje
from bss_sys_area
where bss_sys_area.arealevel = '2') areainfo
leftjoin (
select yybusiness.areaname, sum(yybusiness.cgje) cgje
from (select yybusiness.*,
(select bss_sys_area.areaname
from bss_sys_area
where areaid = yybusiness.parentid) areaname
from (select yybusiness.*,
(select parentid
from bss_sys_area
where areaid = yybusiness.useryydq) parentid
from (select yybusiness.useryyid,
(select dq
from useryy
whereid = yybusiness.useryyid) useryydq,
yybusiness.cgje
from (
select useryy.id useryyid,
useryy.mc useryymc,
yycgd.bm yycgdbm,
yycgd.id yycgdid,
usergys.id usergysid,
usergys.mc usergysmc,
yycgdmx.ypxxid,
ypxx.id,
ypxx.bm,
ypxx.mc,
ypxx.jx,
ypxx.gg,
ypxx.zhxs,
ypxx.scqymc,
ypxx.spmc,
ypxx.jyzt,
(select info
from dictinfo
where ypxx.jyzt = dictcode
and typecode = '003') jyztmc,
(select info
from dictinfo
where typecode = '011'
and dictcode = yycgdmx.cgzt)cgztmc,
yycgdmx.cgl,
yycgdmx.cgje,
yycgdmx.rkl,
yycgdmx.rkje,
yycgdmx.thl,
yycgdmx.thje,
yycgdmx.jsl,
yycgdmx.jsje
from yybusiness2015 yycgdmx,
yycgd2015 yycgd,
useryy,
usergys,
ypxx
where yycgdmx.yycgdid = yycgd.id
and yycgd.useryyid = useryy.id
and yycgdmx.usergysid = usergys.id
and yycgdmx.ypxxid = ypxx.id
)yybusiness) yybusiness) yybusiness) yybusiness
groupby yybusiness.areaname) yybusiness on yybusiness.areaname =
areainfo.areaname