带有WHERE EXISTS的SQL UPDATE语句

Question

我试图写一个更新日期的查询,只有当我更新组的LINE_CD为50.我会这样做吗？

UPDATE EMPLOYER_ADDL  
SET EMPLOYER_ADDL.GTL_UW_APPRV_DT = EMPLOYER_ADDL.DNTL_UW_APPRV_DT 
WHERE EXISTS
    ( 
      SELECT EMP_PLAN_LINE_INFO.LINE_CD
      FROM EMP_PLAN_LINE_INFO
      Where EMP_PLAN_LINE_INFO.GR_NBR = EMPLOYER_ADDL.GR_NBR and
       EMP_PLAN_LINE_INFO.LINE_CD = 50
     )

Answer 1

UPDATE ea
  SET GTL_UW_APPRV_DT = DNTL_UW_APPRV_DT
  FROM EMPLOYER_ADDL AS ea
  WHERE EXISTS
  (
    SELECT 1
      FROM EMP_PLAN_LINE_INFO AS ep
      WHERE ep.GR_NBR = ea.GR_NBR
      AND ep.LINE_CD = 50
  );

但是,如果您可以从查询中获取此信息,为什么要更新表？似乎这样必须经常运行,否则风险就会过时.

Answer 2

那这个呢？

UPDATE ea  
SET ea.GTL_UW_APPRV_DT = ea.DNTL_UW_APPRV_DT 
FROM EMPLOYER_ADDL ea
    INNER JOIN EMP_PLAN_LINE_INFO ei ON(ei.GR_NBR = ea.GR_NBR)
WHERE 
ei.LINE_CD = 50

Answer 3

我相信这会给你相同的结果.

UPDATE ea
  SET GTL_UW_APPRV_DT = DNTL_UW_APPRV_DT
  FROM EMPLOYER_ADDL AS ea
  INNER JOIN EMP_PLAN_LINE_INFO AS ep
      ON ep.GR_NBR = ea.GR_NBR
      AND ep.LINE_CD = 50