表的截斷，刪除和刪除有什麼區別？何時選擇哪個？

Question

表格的truncate,drop和delete有什麼區別？何時選擇哪個？有沒有人有一個快速的比較？我已經看到了很多關於這方面的信息，但還沒有在清晰的概述中找到它。我希望這篇文章有助於理解。

我的意思是像在T-SQL這些語句中使用：

truncate table TableX 
drop table TableX 
delete table_name 

Answer 1

基於由@Michal here答案，多一些搜索我做了下面的語句下面的對比（在T-SQL ）：truncate table TableX，drop table TableX和delete table_name。

      Truncate   Drop     Delete 
Speed      [Fast]    Slow     Slowest 
Rolback possibility  No     No     [Yes] 
Specifiable conditions  No     No     [Yes] 
Scope      All records  All record+Headers Some records/All records 
               =whole table 
Cascading effects   No*    No*     [Yes]** 



**For example: in a Table_1 there is a PK, in Table_2 there is a FK that relates with 
the PK of Table_1, other words there is referential integrity. If the PK has `'ON DELETE CASCADE'` 
and `delete Table_1` is ordered, then the data in Table_2 will be deleted too, 
automatically. For more info about ON DELETE CASCADE and ON ALTER CASCADE, see: 
https://technet.microsoft.com/en-us/library/ms186973%28v=sql.105%29.aspx. 

Cascading does automatic alterations and deletes of depending objects such as foreign keys (FK), 
views, and triggers. Sometimes very useful, sometimes very dangerous.. 

*The drop and truncate statements of a Table_1 (with PK and FK in Table_2, as decribed 
in **) can't be executed, because the ssdms prohibits that. To accomplish the truncation 
or dropping of a Table_1: first get rid of the FK in Table_2, by altering the table design, or 
by dropping table2. 

看到比較基礎的決定時所使用的語句...

作爲一個拇指：

If you want to get rid of only records：當需要一個條件刪除 使用刪除，使用截斷當所有記錄可能會被刪除。當你想能夠回滾然後使用刪除。

If you want to get rid of the whole table，包括標題（帶有設置的列），然後選擇放置。

If you want to get rid of values and automatically the related objects（並且表中定義了級聯），使用delete。 （PS：在其他方言中，即使當表沒有設計級聯時，似乎也有辦法實現它，但據我所知t-sql/msss中沒有;但如果我錯了，請糾正我）

PS：如果你想alter or delete的preferences of a column，然後（在T-SQL方言）使用方法：

阿爾特：

alter table tableX 
alter columnX datatypeX 

刪除：

alter table tableX 
drop column columnX 

---

--And here's some code to play with 
--table to truncate, drop or delete 

create table TableX(
     [Name] [nchar](25) null, 
     [ID_Number] [int] not null) 


--tables with PK and FK 
create table Table_1(
     [Name] [nchar](25) null, 
     [ID_Number] [int] not null primary key) 

create table Table_2(
     [ID_Number] int not null foreign key references Table_1(ID_Number) on delete cascade, 
     [Buys] [int] null) 

--the on delete cascade make it happen that when a ID_Number is Table_1 is deleted, that row 
is automatically deleted in Table_2 too. But not the other way around, 
therefor alter the design of Table_1. 

insert into Table_1 (Name,ID_Number) values ('A',1),('B',2),('C',3); 
insert into Table_2 (ID_Number,Buys) values (1,10),(2,20),(3,30); 

select * from Table_1 
select * from Table_2 

truncate table table_2 
truncate table table_1 

drop table table_2 
drop table table_1 

delete Table_1 

delete from dbo.table_1 where name='A' 
delete from Table_1 where name like '%' 
delete from dbo.table_2 where ID_Number=2