Question

SQL 2008

您好，

我在SQL中必须完成一项相当不同的任务。它比这更复杂，但我会试着让它变得简单。

我需要以某种方式动态地选择列。像这样：

declare @ColName varchar(50)

select @ColName = 'Column1' --This is an actual column name in a real table called 'MyTable'

select @ColName from MyTable where Column2 = 123

有没有办法做这样的事情？任何帮助或方向将不胜感激！

谢谢，杰森

Answer 1

您需要动态SQL，但请先阅读The Curse and Blessings of Dynamic SQL以确保您不会为SQL Injection打开自己

Answer 2

DECLARE @colNameIn AS varchar(50) = 'Column1'

DECLARE @template AS varchar(MAX) = 'select {@ColName} from MyTable where Column2 = 123' -- This template can be expanded

-- Protect yourself from injection or invalid columns:
DECLARE @ColName AS varchar(50)
SELECT @ColName = COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'MyTable' 
    AND COLUMN_NAME = @ColNameIn

IF @ColName IS NOT NULL
BEGIN
    DECLARE @sql AS varchar(MAX)
    SET @sql = REPLACE(@template, '{@ColName}', QUOTENAME(@ColName))
    EXEC (@sql)
END

Answer 3

阅读@SQLMenace答案中的链接！

declare @ColName varchar(50)
select @ColName = 'Column1'

declare @sql varchar(MAX)
select @sql = 'select ' + @ColName + ' MyTable where Column2 = 123'

exec (@sql)

Answer 4

如果已在过程中预定义了所有可接受的列名，则可以使用CASE语句执行此操作。

DECLARE @ColName varchar(50)

SET @ColName = 'Column1'

SELECT CASE @ColName
         WHEN 'Column1' THEN Column1
         WHEN 'Column2' THEN Column2
       END
FROM MyTable
WHERE Column2 = 123

在SP中动态引用SQL Server列

4 个答案: