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  • sql With(NoLock),With(ReadPast)

    ---------------
    create table tmp1
    ( 
        id int primary key,
        name nvarchar(20)
    )
    
    -----------
    insert into tmp1(id,name) values(1,'zhsan1');
    insert into tmp1(id,name) values(2,'lisi1');
    
    -------------------------------
    select * from tmp1


    更新(Update)语句对数据库加锁

    -----------------------------
    begin tran tran1
        update tmp1 set name='zhsan' where id=1
    -------------------------------
    select * from tmp1

    查询一直在进行,此时表已经被锁住了

    -------------------------------
    update tmp1 set name='lisi' where id=2
    -------------------------------
    select * from tmp1 where id>1

    -------------------------------
    delete from tmp1 where id=2
    -------------------------------
    select * from tmp1 where id>1

    查询,更新,删除除被锁定的那行数据都能成功,说明被锁住的只有id=1的那一行,对其他行的查询,更新及删除无影响

    插入语句

    -------------------------------
    insert into tmp1(id,name) values(3,'lisi')
    -------------------------------
    select * from tmp1 where id>1

    结果执行成功,说明插入不受影响


     先将数据库还原为

    -----------------------------
    begin tran tran1
        update tmp1 set name='zhsan' where id=1

    with(readpast)与with(nolock)

    -------------------------------
    select * from tmp1 with(readpast)

    -------------------------------
    select * from tmp1 with(nolock)

    with(readpast)会忽略被锁住的那一行,with(nolock)不会

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  • 原文地址:https://www.cnblogs.com/zhyue93/p/sql_nolock_readpast.html
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