SQL 在 If 和 Else 块中插入临时表

Question

我正在尝试根据 SQL 2005 中条件的结果填充临时表。无论哪种方式，临时表都将具有相同的结构，但将根据条件使用不同的查询来填充。下面的简化示例脚本在 ELSE 块 INSERT INTO 的语法检查中失败，错误为：

已经有一个对象名为 数据库中的“#MyTestTable”。

DECLARE @Id int
SET @Id = 1

IF OBJECT_ID('tempdb..#MyTestTable') IS NOT NULL DROP TABLE #MyTestTable

IF (@Id = 2) BEGIN 
    SELECT 'ABC' AS Letters
    INTO #MyTestTable;
END ELSE BEGIN
    SELECT 'XYZ' AS Letters
    INTO #MyTestTable;
END

我可以在IF/ELSE 语句之前创建临时表，然后在条件块中执行INSERT SELECT 语句，但是该表将有很多列，我试图提高效率。那是唯一的选择吗？或者有什么方法可以使这项工作？

谢谢， 马特

Answer 1

你可以试试这个代码。

IF (CONDITION HERE)
       begin
           select * into #MyTempTable from tablename ....
       end
       ELSE
           truncate table #MyTempTable 
           insert into #MyTempTable 
           select * from tablename ....
       end

谢谢！！！

Answer 2

我试过了：

SELECT S1.* INTO #MytestTable
FROM 
(   SELECT 'ABC' AS Letters WHERE 1 = CASE @Id=2 THEN 1 ELSE 2 END
    UNION
    SELECT 'XYZ' AS Letters WHERE 1 = CASE @Id=1 THEN 1 ELSE 2 END
) AS S1

如果稍后您需要向#MyTestTable 添加列，则此解决方案会更好，因为否则您必须在重新运行脚本之前物理删除它，这在测试条件下很烦人。

Answer 3

如果无法预先创建临时表并且不想将核心逻辑放入动态 SQL 中，我会使用此解决方案。

IF 1 = 1 -- Replace with actual condition
BEGIN
    SELECT * INTO #tmp1 FROM dbo.Table1
END
ELSE
BEGIN
    SELECT * INTO #tmp2 FROM dbo.Table2
END

-- Inserting data into global temp table so sql server can't complain on not recognizing in a context
DECLARE @Command VARCHAR(MAX)
IF OBJECT_ID('tempdb..#tmp1') IS NOT NULL
BEGIN
    SET @Command = 'SELECT * INTO ##tmp FROM #tmp1'
END
ELSE
BEGIN
    SET @Command = 'SELECT * INTO ##tmp FROM #tmp2'
END

EXECUTE(@Command)
SELECT * INTO #tmpFinal FROM ##tmp -- Again passing data back to local temp table from global temp table to avoid seeing red mark

IF OBJECT_ID('tempdb..##tmp') IS NOT NULL DROP TABLE ##tmp
IF OBJECT_ID('tempdb..#tmp1') IS NOT NULL DROP TABLE #tmp1
IF OBJECT_ID('tempdb..#tmp2') IS NOT NULL DROP TABLE #tmp2

SELECT * FROM #tmpFinal

IF OBJECT_ID('tempdb..#tmpFinal') IS NOT NULL DROP TABLE #tmpFinal

Answer 4

回答晚了 8 年，但我很惊讶没有人想到：

select * into #MyTempTable from...
where 1=2

IF -- CONDITION HERE
insert into #MyTempTable select...
ELSE
insert into #MyTempTable select...

简单、快速且有效。不需要动态sql

Answer 5

此代码可能对您有所帮助

--creating temptable using columns of two existing tables
--you can create your temp table Using other methods

select top 0 VI.*,VU.FullName
into #mytemptable
from dbo.Items VI inner join
     dbo.Users as VU 
     on VU.Id=VI.Id

--insert your data base on your condition
if(i<2) --First Condition
begin
INSERT INTO #mytemptable
SELECT VI.*,VU.FullName 
from dbo.Items VI inner join
     dbo.Users as VU 
     on VU.Id=VI.Id
end
Else if(2<i) --Second Condition
begin
INSERT INTO #mytemptable
SELECT VI.*,VU.FullName 
from dbo.Items VI inner join
     dbo.Users as VU 
     on VU.Id=VI.Id
end

select * from #mytemptable --show result

drop table #mytemptable --drop table if its needed

此代码适用于 sql server 2014 我不知道它是否适用于 sql 2005

Answer 6

这是一个老问题，但对于其他来到这里的人来说：

用户 Philip Kelley 给出的动态 SQL 答案不适用于本地临时表 (#Mytemp)。您可以做的是创建动态 SQL 以将其插入到全局临时表 (##MyTemp) 中，以后可以删除该表。

DECLARE @Command  varchar(500)

DECLARE @Id int 
SET @Id = 2

IF OBJECT_ID('tempdb..#MyTestTable') IS NOT NULL DROP TABLE ##MyTestTable 

IF (@Id = 2) BEGIN  
    SET @Command = 'SELECT ''ABC'' AS Letters INTO ##MyTestTable'
END ELSE BEGIN 
    SET @Command = 'SELECT ''XYZ'' AS Letters INTO ##MyTestTable'
END 

EXECUTE (@Command)

select * from ##MyTestTable

DROP ##MyTestTable

Answer 7

您遇到的问题不是您正在填充临时表，而是您正在尝试创建该表。 SQL 解析您的脚本并发现您正试图在两个不同的位置创建它，因此会引发错误。意识到“执行路径”不可能同时命中两个 create 语句是不够聪明的。使用动态 SQL 将不起作用；我试过了

DECLARE @Command  varchar(500)

DECLARE @Id int 
SET @Id = 2

IF OBJECT_ID('tempdb..#MyTestTable') IS NOT NULL DROP TABLE #MyTestTable 

IF (@Id = 2) BEGIN  
    SET @Command = 'SELECT ''ABC'' AS Letters INTO #MyTestTable'
END ELSE BEGIN 
    SET @Command = 'SELECT ''XYZ'' AS Letters INTO #MyTestTable'
END 

EXECUTE (@Command)

select * from #MyTestTable

但临时表只持续与动态会话一样长。所以，唉，看来您必须先声明该表，然后再填充它。编写和支持的代码可能很笨拙，但它会足够高效地执行。

Answer 8

在这两种情况下，您都可以在 SELECTing INTO 之前删除该表。例如：

DECLARE @Id int 
SET @Id = 1  

IF (@Id = 2) BEGIN  
    IF OBJECT_ID('tempdb..#MyTestTable') IS NOT NULL DROP TABLE #MyTestTable
    SELECT 'ABC' AS Letters 
    INTO #MyTestTable; 
END ELSE BEGIN 
    IF OBJECT_ID('tempdb..#MyTestTable') IS NOT NULL DROP TABLE #MyTestTable 
    SELECT 'XYZ' AS Letters 
    INTO #MyTestTable; 
END 

评论后更新：

这很烦人。

两个单独的临时表怎么样？然后在 If/Else 登录后，检查每个是否存在，如果存在，则选择第三个临时表？这可能效果不佳，但这是否重要取决于您需要它的用途。

Answer 9

在您提供的场景中，您可以这样做

DECLARE @Id int
SET @Id = 1

IF OBJECT_ID('tempdb..#MyTestTable') IS NOT NULL DROP TABLE #MyTestTable

SELECT 
  CASE WHEN (@Id = 2) 
    THEN 'ABC' 
    ELSE 'XYZ' 
  END AS Letters
INTO #MyTestTable;

但否则您需要像这样在if statement 之前创建表

Create Table #MyTestTable (
  MyValue varchar(3)
)
IF (@Id = 2) BEGIN 
  Insert Into (MyValue)
  SELECT 'ABC' AS Letters;
END ELSE BEGIN
  Insert Into (MyValue)
  SELECT 'XYZ' AS Letters;
END