在SQL Server中添加表列之前检查表列

我需要在工作中编写一个表修改脚本。他们不想做一个简单的if exists-then-drop-and-create，而是想让它检查我添加的新列，只有在它们不存在时才用它们修改表

有人能帮我写剧本吗？假设一个简单的表当前看起来如下所示：

CREATE TABLE myTable (

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

)

。。我想添加一个地址字段，比如说varchar50，但前提是它在模式中还不存在

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
)

或

像这样的

编辑：我的朋友认为这样更好

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

试试这个：

在这里使用它，您可以检查多个列并更改表

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

---

OP不想丢掉桌子。如果该列不存在，只需添加该列即可

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

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

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