Question

我需要在工作时编写表格修改脚本。他们希望它检查我正在添加的新列，而不是做一个简单的“如果存在然后删除并创建”，只有在它们不存在的情况下才用它们来改变它。

有人可以帮我写剧本吗？假设一个当前看起来像这样的简单表：

CREATE TABLE myTable (

[ID] [int] NOT NULL,
[FirstName] [varchar] (20) NOT NULL,
[LastName] [varchar] (20) NOT NULL

)

..我想添加一个Address字段，varchar（50），但只有在架构中不存在时才会这样。

Answer 1

IF NOT EXISTS(SELECT * FROM INFORMATION_SCHEMA.COLUMNS
    WHERE TABLE_NAME = 'myTable' AND COLUMN_NAME = 'Address')
BEGIN

    ALTER TABLE [dbo].[myTable] ADD 
        [Address] varchar(50) NOT NULL 
END

Answer 2

试试这个

IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[myTable ]') AND type in (N'U'))
BEGIN
 DROP TABLE [dbo].[myTable ]
END

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE myTable (

[ID] [int] NOT NULL,
[FirstName] [varchar] (20) NOT NULL,
[LastName] [varchar] (20) NOT NULL,
[Address] [varchar] (50) NOT NULL
)

OR

if not exists(select * from sys.columns 
            where Name = N'Address' and Object_ID = Object_ID(N'myTable'))    
begin
    alter table myTable
    add Address varchar(50) NOT NULL
end
GO

Answer 3

IF 'col_name' 
NOT IN 
   SELECT Name
   FROM table_name.columns 
ALTER TABLE table_name 
ADD 'col_name' VARCHAR(65) NOT NULL

这样的事情？

编辑：我的朋友认为这好多了

IF NOT EXISTS 
   (SELECT Name
    FROM table_name.columns
    Where Name='target_column_name')
ALTER TABLE table_name
ADD 'target_column_name' VARCHAR(65) NOTNULL

Answer 4

试试这个：

在这里使用它你可以检查多个列并让你改变表...

DECLARE @query VARCHAR(MAX)

IF EXISTS(SELECT * FROM sys.columns
WHERE Name = N'Address' AND OBJECT_ID = OBJECT_ID(N'<TableName>'))
BEGIN
SET   
    @query = 'ALTER TABLE <TableName> ADD Address varchar(50) GO'
END 

--You can give multiple If conditions, example:
--IF EXISTS(SELECT * FROM sys.columns
--WHERE Name = N'<SomeOtherColumn>' AND OBJECT_ID = OBJECT_ID(N'<TableName>'))
--BEGIN
--SET   
    --@query = @query + 'ALTER TABLE <TableName> ADD <SomeOtherColumn> varchar(50) GO'
--END 

EXEC sp_Executesql @query

在SQL Server中添加表列之前检查它们

4 个答案: