oracle的多表合併查詢-工作心得

本隨筆文章，由個人博客（鳥不拉屎）轉移至博客園
發佈時間： 2018 年 11 月 29 日
原地址：https://niaobulashi.com/archives/oracle-select-all.html

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剛剛開發需求寫了個SQL，記個筆記，學習下關於數據庫的多表合併查詢的用法

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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,不過濾重複的數據行

UNION

使用UNION，會將結果集A和結果集B進行UNION ALL運算,然後取兩者交集的餘集作爲結果集

Intersect

使用Intersect,會將結果集A和結果集B進行UNION ALL運算,然後兩者之間的集交集作爲結果集和UNION剛好相反

MINUS

使用MINUS,取結果集A減去結果集B留下的差集,注:如果結果集A小於等於結果集B,返回空結果集.

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好啦，下面進入實戰階段，我就直接將我寫的SQL貼出來吧

select a.*
  from (select t.c_fund_account_name as "fundAccountNo", --基金賬號
               tfp.project_code as "projectCode", --項目編號
               tfp.project_name as "projectName", --項目名稱
               tfp.project_shortname as "projectShortName", --項目簡稱
               c.c_fund_name as "fundName", --基金產品名稱
               c.c_fund_code as "fundCode", --基金產品代碼
               nvl(thold.subsistAssetsShare, 0) as "subsisAssetsShare", --份額（家族）
               to_char(thold.updateDate, 'yyyy-MM-dd') as "updateDate", --日期
               nvl(c.c_current_share, 0) as "currentShare", --份額（基金網站）
               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, -- 持有份額
                           sum(tha.current_cost) as currentCost, --當前成本
                           sum(tha.accumulated_profit) as accumulatedProfit, --累積利潤
                           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' --基金賬戶
           AND t.delete_flag = '0'
        
        UNION ALL
        
        select t.c_fund_account_name as "fundAccountNo", --基金賬號
               tfp.project_code as "projectCode", --項目編號
               tfp.project_name as "projectName", --項目名稱
               tfp.project_shortname as "projectShortName", --項目簡稱
               CAST('' as nvarchar2(50)) as "fundName", --基金產品名稱
               CAST('' as nvarchar2(50)) as "fundCode", --基金產品代碼
               nvl(thold.subsistAssetsShare, 0) as "subsisAssetsShare", --份額（家族）
               to_char(thold.updateDate, 'yyyy-MM-dd') as "updateDate", --日期
               to_number(nvl('', 0)) as "currentShare", --份額（基金網站）
               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, -- 持有份額
                           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具體意思是：查詢出基金信息，A和基金對比先查詢其中有的數據，再union all A有基金沒有的數據，一起取個並集。OK，需求完成
哈哈哈哈，其實只要你SQL寫得牛逼，然後瞭解下業務流程，什麼都好說哈哈哈

哦對了，最後囉嗦一句。 對於這些並集計算之後，需要排序 則語法爲：
select t.* from (語句1 union all 語句2)
t order by t.id;