在將表添加到SQL Server之前檢查表列

Question

我需要在工作中編寫表修改腳本。而不是做一個簡單的「if exists then drop and create」，他們希望它檢查我添加的新列，然後只有在它們不存在的情況下才更改表。

有人可以幫我的腳本？假設一個簡單的表格，看起來像這樣目前：

CREATE TABLE myTable (

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

) 

..我想補充一個Address場，VARCHAR（50）假設，但只有當它沒有在架構已經存在。

Answer 1

試試這個

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 2

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 3

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

這樣的事情？

編輯：我的朋友認爲這是更好的

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

試試這個：

這裏使用它，你可以檢查多個欄目，讓你改變表...

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