Question

首先它应该对DB'es来说很容易，但它真的让我痛苦，我不知道为什么，

我有两个表，[Table1]名为Applicationforms，[Table2]名为WFInstance 我需要使用表2中的startedDate值更新Table1中的FormSubmitDate FormSubmitDate为null。我写了以下查询

UPDATE    ApplicationForm
SET              FormSubmitDate = wfi.StartDate
FROM         ApplicationForm app ,
                      WorkFlowInstances wfi

WHERE     app.FormSubmitDate is null and wfi.applicationID = app.ID

当我运行查询时，SQL会将查询重新生成到这个查询，

UPDATE    ApplicationForm
SET              FormSubmitDate = wfi.StartDate
FROM         ApplicationForm AS app INNER JOIN
                      WorkFlowInstances AS wfi ON app.ID = wfi.ApplicationID CROSS JOIN
                      ApplicationForm
WHERE     (app.FormSubmitDate IS NULL)

我尝试使用join，

写另一个语句

UPDATE ApplicationForm
SET FormSubmitDate = wfi.StartDate
FROM ApplicationForm 
JOIN WorkFlowInstances wfi ON ApplicationForm.ID = wfi.ApplicationID 
WHERE  FormSubmitDate is null

并且SQL生成相同的新语法，

现在当我运行代码时，[所有记录] formSubmitDate字段填充第二个表startDate的第一个值。即使我有一个记录在table1中包含空值

我在这里缺少什么！？

Answer 1

我认为这可以满足您的需求。试一试，告诉我们。

UPDATE tabl3
SET formsubmitdate=(SELECT startdate
  FROM table4
  WHERE table4.id=tabl3.id AND tabl3.formsubmitdate is null);

编写相同内容的另一种方法是

UPDATE tabl3
SET formsubmitdate= startdate
FROM table4 where tabl3.id = table4.id and formsubmitdate is null

从另一个连接列更新列，

1 个答案: