oracle的多表合并查询-工作心得

本随笔文章，由个人博客（鸟不拉屎）转移至博客园
发布时间： 2018 年 11 月 29 日
原地址：https://niaobulashi.com/archives/oracle-select-all.html

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刚刚开发需求写了个SQL，记个笔记，学习下关于数据库的多表合并查询的用法

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  select t.* from A t 
    UNION ALL/UNION/Intersect/MINUS
  select s.* from B s;

UNION ALL

使用UNION ALL，表示取A、B的合集,不过滤重复的数据行

UNION

使用UNION，会将结果集A和结果集B进行UNION ALL运算,然后取两者交集的余集作为结果集

Intersect

使用Intersect,会将结果集A和结果集B进行UNION ALL运算,然后两者之间的集交集作为结果集和UNION刚好相反

MINUS

使用MINUS,取结果集A减去结果集B留下的差集,注:如果结果集A小于等于结果集B,返回空结果集.

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好啦，下面进入实战阶段，我就直接将我写的SQL贴出来吧

select a.*
  from (select t.c_fund_account_name as "fundAccountNo", --基金账号
               tfp.project_code as "projectCode", --项目编号
               tfp.project_name as "projectName", --项目名称
               tfp.project_shortname as "projectShortName", --项目简称
               c.c_fund_name as "fundName", --基金产品名称
               c.c_fund_code as "fundCode", --基金产品代码
               nvl(thold.subsistAssetsShare, 0) as "subsisAssetsShare", --份额（家族）
               to_char(thold.updateDate, 'yyyy-MM-dd') as "updateDate", --日期
               nvl(c.c_current_share, 0) as "currentShare", --份额（基金网站）
               to_char(c.d_date, 'yyyy-MM-dd') as "dateDate", --日期
               (nvl(thold.subsistAssetsShare, 0) - nvl(c.c_current_share, 0)) as "diffValue", --差值
               CAST((CASE
                      WHEN (nvl(thold.subsistAssetsShare, 0) -
                           nvl(c.c_current_share, 0)) = 0 THEN
                       '1'
                      WHEN (nvl(thold.subsistAssetsShare, 0) -
                           nvl(c.c_current_share, 0)) <> 0 THEN
                       '0'
                    END) as nvarchar2(2)) as "identical" --是否一致
          from t_fund_account t
         inner join (select fhs.*,
                           row_number() over(partition by fhs.c_fund_account_no, fhs.c_project_code order by fhs.d_date desc) rn
                      from td_fund_holding_share fhs) c
            on t.c_fund_account_name = c.c_fund_account_no
           and t.c_project_code = c.c_project_code
          LEFT JOIN (SELECT tha.project_code as projectCode,
                           sum(tha.current_share) as subsistAssetsShare, -- 持有份额
                           sum(tha.current_cost) as currentCost, --当前成本
                           sum(tha.accumulated_profit) as accumulatedProfit, --累积利润
                           max(tha.update_time) as updateDate
                      FROM t_hold_assets tha
                      left join t_polling_product p
                        on tha.c_product_code = p.c_product_code
                     WHERE 1 = 1
                       and tha.delete_flag = '0'
                       and p.c_stock_type_level1 = '0'
                       and p.c_stock_type_level2 = '01'
                     GROUP BY tha.project_code) thold
            on thold.projectCode = t.c_project_code
          left join t_family_project tfp
            on tfp.project_code = t.c_project_code
           and tfp.delete_flag = '0'
         where rn = 1
           AND t.c_fund_account_type = '1' --基金账户
           AND t.delete_flag = '0'
        
        UNION ALL
        
        select t.c_fund_account_name as "fundAccountNo", --基金账号
               tfp.project_code as "projectCode", --项目编号
               tfp.project_name as "projectName", --项目名称
               tfp.project_shortname as "projectShortName", --项目简称
               CAST('' as nvarchar2(50)) as "fundName", --基金产品名称
               CAST('' as nvarchar2(50)) as "fundCode", --基金产品代码
               nvl(thold.subsistAssetsShare, 0) as "subsisAssetsShare", --份额（家族）
               to_char(thold.updateDate, 'yyyy-MM-dd') as "updateDate", --日期
               to_number(nvl('', 0)) as "currentShare", --份额（基金网站）
               to_char(CAST('' as nvarchar2(50)), 'yyyy-MM-dd') as "dateDate", --日期
               nvl(thold.subsistAssetsShare, 0) - nvl('', 0) as "diffValue", --差值
               CAST((CASE
                      WHEN (nvl(thold.subsistAssetsShare, 0) - nvl('', 0)) = 0 THEN
                       '1'
                      WHEN (nvl(thold.subsistAssetsShare, 0) - nvl('', 0)) <> 0 THEN
                       '0'
                    END) as nvarchar2(2)) as "identical" --是否一致
          from t_fund_account t
          LEFT JOIN (SELECT tha.project_code as projectCode,
                           sum(tha.current_share) as subsistAssetsShare, -- 持有份额
                           max(tha.update_time) as updateDate
                      FROM t_hold_assets tha
                      left join t_polling_product p
                        on tha.c_product_code = p.c_product_code
                     WHERE 1 = 1
                       and tha.delete_flag = '0'
                       and p.c_stock_type_level1 = '0'
                       and p.c_stock_type_level2 = '01'
                     GROUP BY tha.project_code) thold
            on thold.projectCode = t.c_project_code
          left join t_family_project tfp
            on t.c_project_code = tfp.project_code
           and tfp.delete_flag = '0'
         where t.c_fund_account_name not in
               (select td.c_fund_account_no from td_fund_holding_share td)
           and t.c_fund_account_type = '1'
           and t.delete_flag = '0') a
 order by a."diffValue" desc, a."projectCode" desc

上面sql具体意思是：查询出基金信息，A和基金对比先查询其中有的数据，再union all A有基金没有的数据，一起取个并集。OK，需求完成
哈哈哈哈，其实只要你SQL写得牛逼，然后了解下业务流程，什么都好说哈哈哈

哦对了，最后啰嗦一句。 对于这些并集计算之后，需要排序 则语法为：
select t.* from (语句1 union all 语句2)
t order by t.id;