Sql Oracle更新查询-游标

我想从SecondTable更新FirstTable，但是有很多复杂的地方。 这是主要查询：

UPDATE x.FirstTable Table1
set Table1.UpdatedColumn = (
  SELECT Table2.V_PROD_CODE
  FROM y.SecondTable Table2
  WHERE Table2.XX_V_ACCOUNT_ID1 = Table1.XX_V_ACCOUNT_ID1
  AND Table2.XX_V_ACCOUNT_ID2 = Table1.XX_V_ACCOUNT_ID2
  AND Table2.XX_V_ACCOUNT_ID3 = Table1.XX_V_ACCOUNT_ID3
  AND  Table2.c_Date between '17-Apr-2018' and '27-Apr-2018'
  AND Table2.c_DATE = Table1.c_date)
WHERE Table1.c_date between '17-Apr-2018' and '27-Apr-2018'
AND length(Table1.xx_v_account_id1) = 12;

时间太长了，所以我考虑创建一个光标：

create or replace procedure wco as
  cursor UpdateCursor is 
    SELECT Table2.V_PROD_CODE
    FROM y.SecondTable Table2
    INNER JOIN x.FirstTable Table1 on SUBSTR(Table1.V_CAST_REF_CODE, 6, 8) = SUBSTR(Table2.V_CAST_REF_CODE, 6, 8)
    WHERE Table2.XX_PRODUCT_CODECCOUNT_ID1 = Table1.XX_PRODUCT_CODECCOUNT_ID1
    AND Table2.XX_PRODUCT_CODECCOUNT_ID2 = Table1.XX_PRODUCT_CODECCOUNT_ID2
    AND Table2.XX_PRODUCT_CODECCOUNT_ID3 = Table1.XX_PRODUCT_CODECCOUNT_ID3
    AND  Table2.fic_mis_date between '17-Apr-2018' and '27-Apr-2018'
    AND Table2.c_DATE = Table1.c_date
for update;
    v_PRODUCT_CODE Table2.V_PROD_CODE%type;

begin
  open UpdateCursor;
  loop
    fetch UpdateCursor into v_PRODUCT_CODE;
    exit when UpdateCursor%notfound;

    update XXBADWH.xxba_dwh_instrument_master INST
    set INST.v_product_code = v_PRODUCT_CODE 
    WHERE current of UpdateCursor
    AND INST.fic_mis_date between '17-Apr-2018' and '27-Apr-2018'
    AND length (INST.xx_v_account_id1) = 12;
  end loop;

  close UpdateCursor;
end;


exec wco;

drop procedure wco;

这个查询有什么问题？还有更好的做法吗？

对于此查询：

UPDATE x.FirstTable Table1
    SET Table1.UpdatedColumn = (
            SELECT Table2.V_PROD_CODE
           FROM y.SecondTable Table2
           WHERE Table2.XX_V_ACCOUNT_ID1 = Table1.XX_V_ACCOUNT_ID1 AND
                 Table2.XX_V_ACCOUNT_ID2 = Table1.XX_V_ACCOUNT_ID2 AND
                 Table2.XX_V_ACCOUNT_ID3 = Table1.XX_V_ACCOUNT_ID3 AND
                 Table2.c_Date between DATE '2018-04-17'  and DATE '2018-04-27' AND
                 Table2.c_DATE = Table1.c_date
          )
WHERE Table1.c_date between DATE '2018-04-17' and DATE '2018-04-27' AND
      length(Table1.xx_v_account_id1) = 12;

您需要在

表1（长度（xx_v_账户id1）、c_日期）

和

表2（xx_v_账户id1、xx_v_账户ID2、xx_v_账户ID3、c_日期）

---

我将从索引开始（在

select

select语句中测试）。游标很少是获得更好性能的途径。

解释计划是什么？为什么您希望逐行更新比单个更新语句更快？那么我如何优化它？是什么让您认为查询有问题？错误消息？结果不正确？？？第一个查询花费的时间太长，第二个查询有错误，但显然第二个查询没有解决我们的主要问题，即性能，因为我使用的是游标