Question

我想从SecondTable更新FirstTable，但是有很多麻烦。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;

花费的时间太长，所以我考虑创建一个游标：

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;

查询出了什么问题？以及其他更好的做法？

Answer 1

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;

您要在Table1(length(xx_v_account_id1), c_date)和Table2(XX_V_ACCOUNT_ID1, XX_V_ACCOUNT_ID2, XX_V_ACCOUNT_ID3, c_DATE)上建立索引。

我将从索引开始（在select select语句上进行测试）。游标很少是获得更好性能的途径。

Oracle Update查询-游标

1 个答案: