僅當條件為真時才進行SQL JOIN

Question

我的SQL存儲過程中有3個變量，並且僅在第3個變量不為null時才想添加聯接。

這就是我正在嘗試執行的操作，但是它不起作用。 它在指出的行上給出以下錯誤：

'{'附近的語法不正確

ALTER PROCEDURE [dbo].[Search] 
@one NVARCHAR(50), @two NVARCHAR(50), @three NVARCHAR(50)

SELECT  cinfo.ID,
    cinfo.Nam,
    cinfo.INAM,
    cinfo.CA,
    cinfo.Form,
    cinfo.Std,
    cval.Prop,
    cval.Cons,
    sc.Accep

From dbo.Info AS cinfo
Inner JOIN dbo.values AS cval
    ON cinfo.ID = cval.ID
INNER JOIN dbo.Sources AS sc
    ON (cval.sID = sc.sID AND sc.Accept = 'A')
IF @three IS NOT NULL{               **<---------------------**
LEFT JOIN dbo.Synonym AS synm
    ON cinfo.ID = synm.ID}

where (cinfo.NAM LIKE '%'+@one+'%' OR cinfo.CAS LIKE '%'+@two+'%' OR 
  synm.SynonymID LIKE '%'+@three+'%') AND
    (cval.PropID = '1' OR
    cval.PropID = '2' OR
    cval.PropID = '3' OR
    cval.PropID = '4' OR)

Answer 1

您不能只在聯接上使用and嗎？ 將嘗試進行連接，但是如果@three為null，則不會發生對同義詞的連接....還是出於性能原因您真的需要忽略該連接嗎？ 如果是這樣的話，動態SQL是我可以看到的唯一使它工作的方法...

ALTER PROCEDURE [dbo].[Search] 
@one NVARCHAR(50), @two NVARCHAR(50), @three NVARCHAR(50)

SELECT  cinfo.ID,
    cinfo.Nam,
    cinfo.INAM,
    cinfo.CA,
    cinfo.Form,
    cinfo.Std,
    cval.Prop,
    cval.Cons,
    sc.Accep

From dbo.Info AS cinfo
Inner JOIN dbo.values AS cval
    ON cinfo.ID = cval.ID
INNER JOIN dbo.Sources AS sc
    ON (cval.sID = sc.sID AND sc.Accept = 'A')
LEFT JOIN dbo.Synonym AS synm
    ON cinfo.ID = synm.ID
   and @three IS NOT NULL               **<---------------------**

where (cinfo.NAM LIKE '%'+@one+'%' OR cinfo.CAS LIKE '%'+@two+'%' OR 
  synm.SynonymID LIKE '%'+@three+'%') AND
    (cval.PropID = '1' OR
    cval.PropID = '2' OR
    cval.PropID = '3' OR
    cval.PropID = '4' OR)

Answer 2

這不是正確的語法，但是您可以通過幾種方法來實現，最愚蠢的方法是在頂部添加布爾檢查。

IF @three IS NOT NULL
BEGIN
--FULL QUERY that JOIN dbo.Synonym 
END 

IF @Three IS NULL
BEGIN
--FULL QUERY that does not JOIN dbo.Synonym 
END

或者，您可以使用case..when進行控制時， if

Answer 3

您需要在加入自己時提供該條件。

ALTER PROCEDURE [dbo].[Search] 
@one NVARCHAR(50), @two NVARCHAR(50), @three NVARCHAR(50)

SELECT  cinfo.ID,
    cinfo.Nam,
    cinfo.INAM,
    cinfo.CA,
    cinfo.Form,
    cinfo.Std,
    cval.Prop,
    cval.Cons,
    sc.Accep

From dbo.Info AS cinfo
Inner JOIN dbo.values AS cval
    ON cinfo.ID = cval.ID
INNER JOIN dbo.Sources AS sc
    ON (cval.sID = sc.sID AND sc.Accept = 'A')
       LEFT JOIN dbo.Synonym AS synm
    ON (cinfo.ID = synm.ID and @three is not null) **<---------------------**

where (cinfo.NAM LIKE '%'+@one+'%' OR cinfo.CAS LIKE '%'+@two+'%' OR 
  synm.SynonymID LIKE '%'+@three+'%') AND
    (cval.PropID = '1' OR
    cval.PropID = '2' OR
    cval.PropID = '3' OR
    cval.PropID = '4' OR)

Answer 4

您可以通過構建動態查詢來實現此目標，如下所示

ALTER PROCEDURE [dbo].[Search] 
@one NVARCHAR(50), @two NVARCHAR(50), @three NVARCHAR(50)

DECLARE @query varchar(2000)=' SELECT  cinfo.ID,
    cinfo.Nam,
    cinfo.INAM,
    cinfo.CA,
    cinfo.Form,
    cinfo.Std,
    cval.Prop,
    cval.Cons,
    sc.Accep

From dbo.Info AS cinfo Inner JOIN dbo.values AS cval ON cinfo.ID = cval.ID
INNER JOIN dbo.Sources AS sc ON (cval.sID = sc.sID AND sc.Accept = ''A'')'

IF @three IS NOT NULL
BEGIN
   SET @query = @query + ' LEFT JOIN dbo.Synonym AS synm ON cinfo.ID = synm.ID '
END

SET @query = @query + 'where (cinfo.NAM LIKE ''%' + @one + '%'' OR cinfo.CAS LIKE ''%' + @two + '%'' OR 
  synm.SynonymID LIKE ''%' + @three + '%'') AND
    (cval.PropID = ''1'' OR
    cval.PropID = ''2'' OR
    cval.PropID = ''3'' OR
    cval.PropID = ''4'')'

EXEC(@query)

Answer 5

關於什么：

ALTER PROCEDURE [dbo].[Search] 
@one NVARCHAR(50), @two NVARCHAR(50), @three NVARCHAR(50)

SELECT  cinfo.ID,
    cinfo.Nam,
    cinfo.INAM,
    cinfo.CA,
    cinfo.Form,
    cinfo.Std,
    cval.Prop,
    cval.Cons,
    sc.Accep

From dbo.Info AS cinfo
Inner JOIN dbo.values AS cval
    ON cinfo.ID = cval.ID
INNER JOIN dbo.Sources AS sc
    ON (cval.sID = sc.sID AND sc.Accept = 'A')
LEFT JOIN dbo.Synonym AS synm
    ON (cinfo.ID = synm.ID AND @three IS NOT NULL)

where (cinfo.NAM LIKE '%'+@one+'%' OR cinfo.CAS LIKE '%'+@two+'%' OR 
  synm.SynonymID LIKE '%'+@three+'%') AND
    (cval.PropID = '1' OR
    cval.PropID = '2' OR
    cval.PropID = '3' OR
    cval.PropID = '4' OR)

Answer 6

將IF @three替換為：

 LEFT JOIN (select * from dbo.Synonym  where @three IS NOT NULL) as synm ON cinfo.ID = synm.ID

並驗證ALTER過程語法和LIKE語法。

Answer 7

You cannot use { for if condition just remove '{'

ALTER PROCEDURE [dbo].[Search] 
@one NVARCHAR(50), @two NVARCHAR(50), @three NVARCHAR(50)

SELECT  cinfo.ID,
    cinfo.Nam,
    cinfo.INAM,
    cinfo.CA,
    cinfo.Form,
    cinfo.Std,
    cval.Prop,
    cval.Cons,
    sc.Accep

From dbo.Info AS cinfo
Inner JOIN dbo.values AS cval
    ON cinfo.ID = cval.ID
INNER JOIN dbo.Sources AS sc
    ON (cval.sID = sc.sID AND sc.Accept = 'A')
**IF @three IS NOT NULL**           Remove this line
LEFT JOIN dbo.Synonym AS synm
    ON cinfo.ID = synm.ID}

where (cinfo.NAM LIKE '%'+@one+'%' OR cinfo.CAS LIKE '%'+@two+'%' OR 
  synm.SynonymID LIKE '%'+@three+'%') AND
    (cval.PropID = '1' OR
    cval.PropID = '2' OR
    cval.PropID = '3' OR
    cval.PropID = '4' OR)

嘗試寫類似IF @@ three is not NULL ALTER PROCEDURE [dbo]。[搜索] @one NVARCHAR（50），@ two NVARCHAR（50），@ three NVARCHAR（50）

SELECT  cinfo.ID,
    cinfo.Nam,
    cinfo.INAM,
    cinfo.CA,
    cinfo.Form,
    cinfo.Std,
    cval.Prop,
    cval.Cons,
    sc.Accep

From dbo.Info AS cinfo
Inner JOIN dbo.values AS cval
    ON cinfo.ID = cval.ID
INNER JOIN dbo.Sources AS sc
    ON (cval.sID = sc.sID AND sc.Accept = 'A')

where (cinfo.NAM LIKE '%'+@one+'%' OR cinfo.CAS LIKE '%'+@two+'%' OR 
  synm.SynonymID LIKE '%'+@three+'%') AND
    (cval.PropID = '1' OR
    cval.PropID = '2' OR
    cval.PropID = '3' OR
    cval.PropID = '4' OR)

結束其他程序[dbo]。[搜索] @one NVARCHAR（50），@ two NVARCHAR（50），@ three NVARCHAR（50）

SELECT  cinfo.ID,
    cinfo.Nam,
    cinfo.INAM,
    cinfo.CA,
    cinfo.Form,
    cinfo.Std,
    cval.Prop,
    cval.Cons,
    sc.Accep

From dbo.Info AS cinfo
Inner JOIN dbo.values AS cval
    ON cinfo.ID = cval.ID
INNER JOIN dbo.Sources AS sc
    ON (cval.sID = sc.sID AND sc.Accept = 'A')
LEFT JOIN dbo.Synonym AS synm
    ON cinfo.ID = synm.ID}

where (cinfo.NAM LIKE '%'+@one+'%' OR cinfo.CAS LIKE '%'+@two+'%' OR 
  synm.SynonymID LIKE '%'+@three+'%') AND
    (cval.PropID = '1' OR
    cval.PropID = '2' OR
    cval.PropID = '3' OR
    cval.PropID = '4' OR).. rest code

結束