use XTS --步驟一=============創建測試表=================================================== --測試表1 if(exists(select 1 from sysobjects where id=OBJECT_ID('testa')))drop table testa CREATE TABLE testa (id int primary key,--Id,并標記為主建name varchar(10),--姓名age decimal(26,4),--年齡city varchar(10),--所在城市address varchar(10),--家庭地址remark text --備注 ) --創建非聚集索引 create unique nonclustered index testa_idx1 on testa(name,age) --測試表2 if(exists(select 1 from sysobjects where id=OBJECT_ID('testb')))drop table testb CREATE TABLE testb (id int primary key,--Id,并標記為主建name varchar(10),--姓名age decimal(26,4),--年齡city varchar(10),--所在城市address varchar(10),--家庭地址remark text --備注 )--創建非聚集索引 create unique nonclustered index testb_idx1 on testb(name,age) --步驟二===================添加測試數據================================================ insert into testa(id,name,age,city,address) select 1,'joe',20,'hz','zjwz'insert into testa(id,name,age,city,address) select 2,'jill',25,'hz','zjhz'insert into testa(id,name,age,city,address) select 3,'Bob',27,'hz','zjhz'insert into testb(id,name,age,city,address) select 1,'joe',20,'hz','zjwz'insert into testb(id,name,age,city,address) select 2,'jill',25,'hz','zjhz'insert into testb(id,name,age,city,address) select 3,'Bob',27,'hz','zjhz'--添加多一點,是為了查詢效率降低，以便快速得到驗證結果 declare @i int=4 while (@i<1000) begininsert into testa(id,name,age,city,address) select @i,@i,27,'xxxx','xxxx' set @i=@i+1 end--步驟三===================創建測試存儲過程及備用表================================================ IF OBJECT_ID ('p1') IS NOT NULL DROP PROC p1 IF OBJECT_ID ('p2') IS NOT NULL DROP PROC p2 --創建備份表，用于查詢存儲過程的結果存儲 if(exists(select 1 from sysobjects where id=OBJECT_ID('testback')))drop table testback CREATE TABLE testback (id int primary key,--Id,并標記為主建name varchar(10),--姓名age decimal(26,4),--年齡city varchar(10),--所在城市address varchar(10)--家庭地址 )if(exists(select 1 from sysobjects where id=OBJECT_ID('testback1')))drop table testback1 CREATE TABLE testback1 (id int primary key,--Id,并標記為主建name varchar(10),--姓名age decimal(26,4),--年齡city varchar(10),--所在城市address varchar(10)--家庭地址 )if(exists(select 1 from sysobjects where id=OBJECT_ID('testback2')))drop table testback2 CREATE TABLE testback2 (id int primary key,--Id,并標記為主建name varchar(10),--姓名age decimal(26,4),--年齡city varchar(10),--所在城市address varchar(10)--家庭地址 )--創建存儲過程p1,更新存儲過程 CREATE PROC p1 ASUPDATE testa SET age = age+1 WHERE id = 1UPDATE testa SET age = age-1 WHERE id = 1 GO--創建存儲過程p2,查詢存儲過程 CREATE PROC p2 AS truncate table testback insert into testback(id,name,age,address) select id,name,age,address from testa where name='joe' GO---死鎖案例一============兩個事物各占有自己的資源，同時又需要對方的資源================== --查詢一 begin transaction update a set address='TT' from testa a where id=1 waitfor delay '00:00:10' select * from testb where id=1 commit transaction --查詢二 begin transaction update a set address='TT' from testb a where id=1 waitfor delay '00:00:10' select * from testa where id=1 commit transaction--死鎖案例二============書簽查詢引起的死鎖============================================= --高頻率update while (1=1) exec p1--高頻率select while (1=1) exec p2Set statistics profile off UPDATE testa SET age = age+1 WHERE id = 1 select id,name,age,address from testa where name='joe'--死鎖三================在較高隔離級別的事務中,兩個事務同時執行查詢及更新語句============ --查詢事務一 --需要設置事務隔離級別可重復瀆或加事務保持鎖 SET TRANSACTION ISOLATION LEVEL Repeatable read while(1=1) begin begin transaction truncate table testback1 insert into testback1(id,name,age,address) select id,name,age,address from testa where id=1 waitfor delay '00:00:10' update testa set age=age+1 where id=1 update testa set age=age-1 where id=1 commit transaction end--查詢事務二 SET TRANSACTION ISOLATION LEVEL Repeatable read while(1=1) begin begin transaction truncate table testback2 insert into testback2(id,name,age,address) select id,name,age,address from testa where id=1 waitfor delay '00:00:10' update testa set age=age+1 where id=1 update testa set age=age-1 where id=1 commit transaction end--死鎖四===========同一個表當兩個事務都在更新不同的記錄時,即使沒有更新索上的字段， --也會引起死鎖,因為查詢的字段沒有全部在所建的普通索引上面,所以同樣需要通過聚集索引做全表查詢 --但是聚集索引上的行在同一時間點上被不同事務在擁有,這樣就造成了兩個事務查詢的時候都無法獲取 --全部的資源，即造成了死鎖 --測試數據如下 drop table testx create table testx(id int primary key,name varchar(10),age int) create index testx_ind1 on testx(name) insert into testx(id,name,age) select '1','袁*','22' insert into testx(id,name,age) select '2','程*','20'create table testx1(id int primary key,name varchar(10),age int) create table testx2(id int primary key,name varchar(10),age int)--查詢一 while(1=1) begin begin transaction update testx set age=age+1 where name='程*' truncate table testx1 insert into testx1(id,name,age) select id,name,age from testx where name='程*' commit transaction end--查詢二 while(1=1) begin begin transaction update testx set age=age+1 where name='袁*' truncate table testx2 insert into testx2(id,name,age) select id,name,age from testx where name='袁*' commit transaction end--那你們可能就會有疑問,那我是不是單純更新,不做查詢的時候也會死鎖？因為更新如果也是通過非主鍵字段更新時，也是全表掃描。 --答案：不會，至于為什么不會，我們只能理解數據庫本身在更新和查詢時上鎖的原理不一樣，這個我們也可以做個測試例子。 --查詢一=====事務A更新20秒后結束 begin transaction update testx set age=40 where name='程*' waitfor delay '00:00:20' commit transaction--查詢二======事務B在5秒后結束 begin transaction update testx set age=40 where name='袁*' waitfor delay '00:00:05' commit transaction--查詢三====再分開執行下面兩個查詢 select * from testx where name='袁*' select * from testx where name='程*'--測試結果: --當我們依次執行查詢一,再執行查詢二，最后執行查詢三: --結果就是查詢二5秒后(不需要等待查詢一完成)就執行完成了，而查詢三無論執行那個查詢語句都需要等待20秒后（即必須要等待查詢一完成）才能出來查詢查詢結果 --結論就是更新和查詢時上鎖原理不一樣。--=================隔離級別的演示============================= DBCC USEROPTIONS --未提交讀（Read uncommitted）演示 --查詢一 SET TRANSACTION ISOLATION LEVEL Read uncommitted select * from testa where id=100 begin transaction update testa set city='newxx' where id=100 waitfor delay '00:00:10' rollback transaction --查詢二 SET TRANSACTION ISOLATION LEVEL Read uncommitted select * from testa where id=100--已提交讀（Read committed）也叫不可重復瀆 --查詢一 SET TRANSACTION ISOLATION LEVEL Read committed select * from testa where id=100 begin transaction update testa set city='newx' where id=100 waitfor delay '00:00:10' rollback transaction --查詢二 SET TRANSACTION ISOLATION LEVEL Read committed select * from testa where id=100--可重復讀（Repeatable read）演示(保證在同一個事務中，瀆取數據不會被其他事務更改) --查詢一 SET TRANSACTION ISOLATION LEVEL Repeatable read begin transaction select * from testa where id=100 waitfor delay '00:00:10' commit transaction--查詢二 SET TRANSACTION ISOLATION LEVEL Repeatable read update testa set city='new' where id=100--可序列化演示(事務的最高級別，保證事務的串行執行) --查詢一 SET TRANSACTION ISOLATION LEVEL Serializable begin transaction select * from testa update testa set city='new' where id=100 waitfor delay '00:00:10' select * from testa commit transaction --查詢二 SET TRANSACTION ISOLATION LEVEL Serializable insert into testa(id,name,age,city,address) select 4000,'Bobx',27,'hz','zjhz'--創建覆蓋索引 drop index testa_idx1 on testa create index testa_idx1 on testa(name,age) include(id,address)--設置隔離級別為可重復瀆 SET TRANSACTION ISOLATION LEVEL Repeatable read DBCC USEROPTIONS --開啟事務隔離的方法 declare @sql varchar(8000) select @sql = ' ALTER DATABASE ' + DB_NAME() + ' SET SINGLE_USER WITH ROLLBACK IMMEDIATE ; ALTER DATABASE ' + DB_NAME() + ' SET TRANSACTION ISOLATION LEVEL read committed; ALTER DATABASE ' + DB_NAME() + ' SET MULTI_USER;' Exec(@sql) --查詢事務隔離 DBCC Useroptions --清除緩存 DBCC DROPCLEANBUFFERS DBCC FREEPROCCACHE DBCC FREESYSTEMCACHE('ALL') --開啟SQL性能分析 Set statistics profile on--開啟SQL執行時間統計 set statistics time ON --開啟磁盤的讀寫統計 set statistics io on--鎖查詢相關 SELECT request_session_id, resource_type, resource_associated_entity_id, request_status, request_mode, resource_description FROM sys.dm_tran_locksselect request_session_id spid,OBJECT_NAME(resource_associated_entity_id) tableName from sys.dm_tran_locks where resource_type='OBJECT'sp_lock sp_who select * from sys.sysprocesses dbcc inputbuffer(spid)

總結

以上是生活随笔為你收集整理的SQL常见死锁例子及分析的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。