为什么SQL在没有检测到更改时更新某些行？

Question

我有一个声明，我用来添加或更新一行数据。我在观察SQL更新行时没有明显的变化。我试图弄清楚SQL为什么要阻止它更新的原因。

我以这种方式更新约1,000行（一个接一个），只有2行似乎更新时，我创建的掩码建议他们不应该。

下面是相关的SQL代码片段：

... 
ELSE IF NOT EXISTS (
    SELECT PERMIT_STATUS, PERMIT_LOCATION, PERMIT_COMMODITY, PERMIT_TYPE_CODE, PERMIT_TYPE_DESCRIPTION, PERMIT_ALLOCATION_METHOD, PERMIT_OPERATION_NAME, OWNERS, SHARE_PERCENTAGE, OPERATOR, MINERALS, PERMIT_DURATION_YEARS, PERMIT_DURATION_MONTHS, PERMIT_AREA, PERMIT_AREA_UNIT, PERMIT_OFFSHORE_ONSHORE, PERMIT_STATUS_DATE, PERMIT_MINERAL_GROUP, PERMIT_MP, SUBSEQUENT_TO_PERMIT, PERMIT_COMMENCEMENT_DATE, PERMIT_EXPIRY_DATE, PERMIT_GRANT_DATE, PERMIT_NONEXCLUSIVE_YN, ShapeGeoJson, Removed 
    FROM MyTable 
    WHERE PERMIT_NUMBER = @PERMIT_NUMBER 
    INTERSECT 
    SELECT @PERMIT_STATUS, @PERMIT_LOCATION, @PERMIT_COMMODITY, @PERMIT_TYPE_CODE, @PERMIT_TYPE_DESCRIPTION, @PERMIT_ALLOCATION_METHOD, @PERMIT_OPERATION_NAME, @OWNERS, @SHARE_PERCENTAGE, @OPERATOR, @MINERALS, @PERMIT_DURATION_YEARS, @PERMIT_DURATION_MONTHS, @PERMIT_AREA, @PERMIT_AREA_UNIT, @PERMIT_OFFSHORE_ONSHORE, @PERMIT_STATUS_DATE, @PERMIT_MINERAL_GROUP, @PERMIT_MP, @SUBSEQUENT_TO_PERMIT, @PERMIT_COMMENCEMENT_DATE, @PERMIT_EXPIRY_DATE, @PERMIT_GRANT_DATE, @PERMIT_NONEXCLUSIVE_YN, @ShapeGeoJson, @Removed 
) 
BEGIN 
    UPDATE MyTable 
    SET PERMIT_STATUS = @PERMIT_STATUS 
     ,PERMIT_LOCATION = @PERMIT_LOCATION 
     ,PERMIT_COMMODITY = @PERMIT_COMMODITY 
     ,PERMIT_TYPE_CODE = @PERMIT_TYPE_CODE 
     ,PERMIT_TYPE_DESCRIPTION = @PERMIT_TYPE_DESCRIPTION 
     ,PERMIT_ALLOCATION_METHOD = @PERMIT_ALLOCATION_METHOD 
     ,PERMIT_OPERATION_NAME = @PERMIT_OPERATION_NAME 
     ,OWNERS = @OWNERS 
     ,SHARE_PERCENTAGE = @SHARE_PERCENTAGE 
     ,OPERATOR = @OPERATOR 
     ,MINERALS = @MINERALS 
     ,PERMIT_DURATION_YEARS = @PERMIT_DURATION_YEARS 
     ,PERMIT_DURATION_MONTHS = @PERMIT_DURATION_MONTHS 
     ,PERMIT_AREA = @PERMIT_AREA 
     ,PERMIT_AREA_UNIT = @PERMIT_AREA_UNIT 
     ,PERMIT_OFFSHORE_ONSHORE = @PERMIT_OFFSHORE_ONSHORE 
     ,PERMIT_STATUS_DATE = @PERMIT_STATUS_DATE 
     ,PERMIT_MINERAL_GROUP = @PERMIT_MINERAL_GROUP 
     ,PERMIT_MP = @PERMIT_MP 
     ,SUBSEQUENT_TO_PERMIT = @SUBSEQUENT_TO_PERMIT 
     ,PERMIT_COMMENCEMENT_DATE = @PERMIT_COMMENCEMENT_DATE 
     ,PERMIT_EXPIRY_DATE = @PERMIT_EXPIRY_DATE 
     ,PERMIT_GRANT_DATE = @PERMIT_GRANT_DATE 
     ,PERMIT_NONEXCLUSIVE_YN = @PERMIT_NONEXCLUSIVE_YN 
     ,ShapeGeoJson = @ShapeGeoJson 
     ,UpdatedUtc = GETUTCDATE() 
     ,Removed = @Removed 
     ,UpdatedMask = (
      IIF (PERMIT_STATUS != @PERMIT_STATUS, 4096, 0) + 
      IIF (PERMIT_LOCATION != @PERMIT_LOCATION, 256, 0) + 
      IIF (PERMIT_COMMODITY != @PERMIT_COMMODITY, 512, 0) + 
      IIF (PERMIT_TYPE_CODE != @PERMIT_TYPE_CODE, 64, 0) + 
      IIF (PERMIT_TYPE_DESCRIPTION != @PERMIT_TYPE_DESCRIPTION, 128, 0) + 
      IIF (PERMIT_ALLOCATION_METHOD != @PERMIT_ALLOCATION_METHOD, 1024, 0) + 
      IIF (PERMIT_OPERATION_NAME != @PERMIT_OPERATION_NAME, 2048, 0) + 
      IIF (OWNERS != @OWNERS, 1048576, 0) + 
      IIF (SHARE_PERCENTAGE != @SHARE_PERCENTAGE, 2097152, 0) + 
      IIF (OPERATOR != @OPERATOR, 4194304, 0) + 
      IIF (MINERALS != @MINERALS, 8388608, 0) + 
      IIF (PERMIT_DURATION_YEARS != @PERMIT_DURATION_YEARS, 32768, 0) + 
      IIF (PERMIT_DURATION_MONTHS != @PERMIT_DURATION_MONTHS, 65536, 0) + 
      IIF (PERMIT_AREA != @PERMIT_AREA, 67108864, 0) + 
      IIF (PERMIT_AREA_UNIT != @PERMIT_AREA_UNIT, 134217728, 0) + 
      IIF (PERMIT_OFFSHORE_ONSHORE != @PERMIT_OFFSHORE_ONSHORE, 262144, 0) + 
      IIF (PERMIT_STATUS_DATE != @PERMIT_STATUS_DATE, 8192, 0) + 
      IIF (PERMIT_MINERAL_GROUP != @PERMIT_MINERAL_GROUP, 131072, 0) + 
      IIF (PERMIT_MP != @PERMIT_MP, 524288, 0) + 
      IIF (SUBSEQUENT_TO_PERMIT != @SUBSEQUENT_TO_PERMIT, 33554432, 0) + 
      IIF (PERMIT_COMMENCEMENT_DATE != @PERMIT_COMMENCEMENT_DATE, 16, 0) + 
      IIF (PERMIT_EXPIRY_DATE != @PERMIT_EXPIRY_DATE, 32, 0) + 
      IIF (PERMIT_GRANT_DATE != @PERMIT_GRANT_DATE, 8, 0) + 
      IIF (PERMIT_NONEXCLUSIVE_YN != @PERMIT_NONEXCLUSIVE_YN, 16384, 0) + 
      IIF (ShapeGeoJson != @ShapeGeoJson, 137438953472, 0) + 
      IIF (Removed != @Removed, 274877906944, 0) 
     ) 
    WHERE PERMIT_NUMBER = @PERMIT_NUMBER; 
END 
... 

我使用顶部的INTERSECT方法来检测任何行的数据列的变化。这是因为比较列中的NULL值更容易。

而且您可以看到UpdatedMask正在更新一个值，以指示哪些列已更新。发生问题时，将其设置为0（并且按预期工作时，我会看到正确的UpdatedMask）。

我看不到任何拼写错误或明显的逻辑错误。所以我想知道是否可能是由于SQL Azure负载不知何故，通过大量的ShapeGeoJson列逐个更新这么多的记录？

这里的表定义的情况下，它是非常有用的：

CREATE TABLE [dbo].[MyTable](
    [PERMIT_NUMBER] [varchar](30) NOT NULL, 
    [PERMIT_STATUS] [varchar](30) NULL, 
    [PERMIT_LOCATION] [varchar](4000) NULL, 
    [PERMIT_COMMODITY] [varchar](8) NULL, 
    [PERMIT_TYPE_CODE] [varchar](4000) NULL, 
    [PERMIT_TYPE_DESCRIPTION] [varchar](255) NULL, 
    [PERMIT_ALLOCATION_METHOD] [varchar](4000) NULL, 
    [PERMIT_OPERATION_NAME] [varchar](4000) NULL, 
    [OWNERS] [varchar](4000) NULL, 
    [SHARE_PERCENTAGE] [varchar](4000) NULL, 
    [OPERATOR] [varchar](220) NULL, 
    [MINERALS] [varchar](4000) NULL, 
    [PERMIT_DURATION_YEARS] [varchar](4000) NULL, 
    [PERMIT_DURATION_MONTHS] [varchar](4000) NULL, 
    [PERMIT_AREA] [varchar](4000) NULL, 
    [PERMIT_AREA_UNIT] [varchar](4) NULL, 
    [PERMIT_OFFSHORE_ONSHORE] [varchar](4000) NULL, 
    [PERMIT_STATUS_DATE] [date] NULL, 
    [PERMIT_MINERAL_GROUP] [varchar](4000) NULL, 
    [PERMIT_MP] [varchar](4000) NULL, 
    [SUBSEQUENT_TO_PERMIT] [varchar](4000) NULL, 
    [PERMIT_COMMENCEMENT_DATE] [date] NULL, 
    [PERMIT_EXPIRY_DATE] [date] NULL, 
    [PERMIT_GRANT_DATE] [date] NULL, 
    [PERMIT_NONEXCLUSIVE_YN] [char](1) NULL, 
    [ShapeGeoJson] [varchar](max) NOT NULL, 
    [CreatedUtc] [datetime] NOT NULL, 
    [UpdatedUtc] [datetime] NOT NULL, 
    [Removed] [bit] NOT NULL, 
    [UpdatedMask] [bigint] NULL, 
CONSTRAINT [PK_MyTable_1] PRIMARY KEY CLUSTERED 
(
    [PERMIT_NUMBER] ASC 
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] 
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY] 

任何想法？

更新过程每晚都会运行，因此我会密切关注那些似乎违反规则的行，以查看是否存在某种模式。我现在已经看过几次了，但忽略了保留之前调查的数据。

Answer 1

我设法深入了解问题。计算UpdatedMask值的逻辑在比较时没有考虑NULL值。

所以更新是有效的。这是计算的UpdatedMask，它是无效的。

所以，现在我已经变丑我的SQL更进一步：

UpdatedMask = (
    IIF (ISNULL(PERMIT_STATUS, '') != ISNULL(@PERMIT_STATUS, ''), 4096, 0) + 
    IIF (ISNULL(PERMIT_LOCATION, '') != ISNULL(@PERMIT_LOCATION, ''), 256, 0) + 
    ... 
) 

Answer 2

在你的代码中你有代码重复。您有INTERSECT/EXISTS部分，您可以检查是否更新了某些内容，然后您将代码计算出UpdatedMask，然后重复逻辑。

我会建议先删除重复的逻辑。那么发现问题并将其修复到一个地方会容易得多。

下面的代码显示了更新记录的另一种方法，只依靠代码来计算UpdatedMask。

-- We will update MyTable from data in the NewData alias that contains 
-- all of the new values and UpdatedMask 
UPDATE U 
SET U.PERMIT_STATUS = NewData.PERMIT_STATUS 
    ,U.PERMIT_LOCATION = NewData.PERMIT_LOCATION 
    .... all other columns .... 
    ,U.UpdatedMask = NewData.UpdatedMask 
FROM MyTable U 
    INNER JOIN (
     SELECT T.PERMIT_STATUS = @PERMIT_STATUS 
      ,T.PERMIT_LOCATION = @PERMIT_LOCATION 
      ... all other columns ... 
      ,UpdatedMask = (
       IIF (T.PERMIT_STATUS != @PERMIT_STATUS, 4096, 0) + 
       IIF (T.PERMIT_LOCATION != @PERMIT_LOCATION, 256, 0) + 
       ... all other columns .... 
      ) 
     FROM MyTable T 
     WHERE T.PERMIT_NUMBER = @PERMIT_NUMBER 
    -- In the join clause we only take rows that are actually updated 
    ) AS NewData ON NewData.UpdatedMask<>0 
WHERE U.PERMIT_NUMBER = @PERMIT_NUMBER;