Question

相当简单的sql过程，当记录落在两个日期之间时，查看表中的字段是否等于true。目的是计算tue的实例，如果计数在输出参数中返回多个，则返回true。

    CREATE PROCEDURE dbo.CheckIfLandingsForPeriodHaveBeenPosted @startDate DATE,
@endDate DATE,
@LandingsPosted BIT OUTPUT

AS
BEGIN
  SET NOCOUNT ON


  IF (SELECT 
        COUNT (
        lh.Posted
      FROM LandingHeaders lh
      WHERE lh.LandingDate1 BETWEEN @startDate AND @endDate
      AND lh.Posted = 1)
    > 0
    SET @LandingsPosted = 1
  ELSE
    SET  @LandingsPosted = 0

END
GO

我尝试在lh.Posted = 1之后添加一个额外的括号并在ELSE之后立即删除SET语句但是没有帮助。

首先，我想知道为什么会在else语句中失败，但我也想知道是否有更优雅/有效的方法来创建这样的查询;在伪代码方面的内容如下：

检查这两个日期之间记录中的已过帐字段，如果发现任何一个为真，则返回true

Answer 1

一种紧凑且高效的解决方案，完全避免使用IF ... ELSE和COUNT：

CREATE PROCEDURE dbo.CheckIfLandingsForPeriodHaveBeenPosted
    @startDate DATE, @endDate DATE,
    @LandingsPosted BIT = 0 OUTPUT   --<- Set default to FALSE
AS
BEGIN
    SELECT TOP 1 @LandingsPosted = 1 --<- Change to TRUE if at least one match is found
    FROM LandingHeaders lh
    WHERE lh.LandingDate1 BETWEEN @startDate AND @endDate
      AND lh.Posted = 1
END
GO

Answer 2

您忘了关注COUNT并)尝试关注：

    CREATE PROCEDURE dbo.CheckIfLandingsForPeriodHaveBeenPosted @startDate DATE,
@endDate DATE,
@LandingsPosted BIT OUTPUT

AS
BEGIN
  SET NOCOUNT ON


  IF (SELECT 
        COUNT(lh.Posted)
      FROM LandingHeaders lh
      WHERE lh.LandingDate1 BETWEEN @startDate AND @endDate
      AND lh.Posted = 1)
    > 0
    SET @LandingsPosted = 1
  ELSE
    SET  @LandingsPosted = 0

END
GO

Answer 3

这是一个简单的语法问题，因为您可以看到我所做的唯一更改是计数，您错过了一个＆＃39;）＆＃39;所以你查询无法编译。

该过程抛出一个错误，并不总是告诉你问题出在哪里，你可以随时认为问题就在它所说的位置。

CREATE PROCEDURE dbo.CheckIfLandingsForPeriodHaveBeenPosted @startDate DATE,
 @endDate DATE,
 @LandingsPosted BIT OUTPUT

AS
BEGIN
  SET NOCOUNT ON


 IF (SELECT 
    COUNT (lh.Posted)
  FROM LandingHeaders lh
  WHERE lh.LandingDate1 BETWEEN @startDate AND @endDate
  AND lh.Posted = 1)
> 0
SET @LandingsPosted = 1
ELSE
SET  @LandingsPosted = 0

END
GO

为什么此过程在编译时会在Else处抛出错误

3 个答案: