如何使用SQL

Question

表分割成多個表

您好我有這個表汽車：

MODEL nvarchar(20) 
STYLE nvarchar(20) 
ENGINE nvarchar(5) 
CAPACITY smallint 
MAX_SPEED smallint 
PRICE smallmoney 
MARKET nvarchar(20) 
COMPETITOR nvarchar(20) 

而且我想通過SQL查詢到它拆分成3個表：

汽車：

MODEL nvarchar(20) 
STYLE nvarchar(20) 
MAX_SPEED smallint 
PRICE smallmoney 

引擎：

ENGINE nvarchar(5) 
CAPACITY smallint 

市場：

MARKET nvarchar(20) 
COMPETITOR nvarchar(20) 

所以徘徊這將如何使用SQL命令來完成，由於

Answer 1

最簡單的方法。選擇...進入將創建新表格：

SELECT DISTINCT 
    ENGINE, 
    CAPACITY 
INTO Engine 
FROM CARS 


SELECT DISTINCT 
    MARKET, 
    COMPETITOR 
INTO Market 
FROM CARS 

然後，只需從原始表中刪除已停用的列。例如：

ALTER TABLE Cars DROP COLUMN ENGINE 
ALTER TABLE Cars DROP COLUMN CAPACITY 
ALTER TABLE Cars DROP COLUMN MARKET 
ALTER TABLE Cars DROP COLUMN COMPETITOR 

這將會明確地提出你在問什麼。然而，我不確定那是否是你想要的 - 那麼汽車沒有提及引擎或市場細節 - 所以信息就會丟失。

如果「ENGINE」和「MARKET」定義了新表的鍵，我建議將這些列作爲外鍵留在車臺上。例如只有DROP能力和競爭對手。

您也可能希望在新表上創建主鍵。例如： ALTER TABLE ENGINE ADD CONSTRAINT [PK_Engine] PRIMARY KEY CLUSTERED ENGINE ASC

Answer 2

是的，它是可能的，它被稱爲「歸化」。

Answer 3

要正常化這些表，您首先需要create新表，寫入SQL到insert將數據寫入新表，然後alter原表中。

見http://technet.microsoft.com/en-us/library/ms174979.aspx 和http://technet.microsoft.com/en-us/library/dd776381(v=sql.105).aspx和http://msdn.microsoft.com/en-us/library/ms190273.aspx

Answer 4

運行此....

create table Engine 
(
    EngineId int identity(1,1) not null primary key, 
    Engine nvarchar(5) not null, 
    Capacity smallint not null 
) 
go 

insert into Engine 
(Engine, Capacity) 
(select distinct Engine,Capacity from Cars) 
go 

alter table Cars 
add EngineId int null 
go 

update Cars 
set Cars.EngineId = e.EngineId 
from Engine e where e.Engine = Cars.Engine 
go 


create table Market 
(
    Id int identity(1,1) not null primary key, 
    Market nvarchar(20) not null, 
    Competitor nvarchar(20) not null 
) 
go 

insert into Market 
(Market, Competitor) 
(select distinct Market,Competitor from Cars) 
go 

alter table Cars 
add MarketId int null 
go 

update Cars 
set Cars.MarketId = m.MarketId 
from Market m where m.Market = Cars.Market 
go 


alter table Cars 
drop column Market; 


alter table Cars 
drop column Competitor; 


alter table Cars 
drop column Engine; 


alter table Cars 
drop column Capacity;