dongqie5529 2015-11-25 21:15
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在MySQL中获取未提交的数据

In SQL Server we can write below SQL Queries to get Un-Committed data in database . This means the data that is still under transaction and Transaction is not complete.

SQL Server Query

Select * from TableName With(NoLock);

Is there any equivalence in MySQL database to get data even if table is locked ? I am trying this in PHP CodeIgnitor

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  • douheng8629 2015-11-25 21:40
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    Only the InnoDB storage engine fully supports transactions. It also implements Oracle/PostgreSQL-style MVCC that prevents implicit row locks from blocking reads. To get Read-Uncommitted in InnoDB, issue a SET TRANSACTION LEVEL READ UNCOMMITTED before issuing the query.

    The syntax for doing so in PHP would look something like this:

    $dbh->exec('SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED');
    $dbh->beginTransaction();
    

    This sets the isolation level until the next COMMIT or ROLLBACK. To make the level change persist for the duration of the session, use

    SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
    

    instead.

    As for overriding a non-sharing read lock on a table or row, I'm not sure that's possible, nor can I think of a situation where it would be desirable. Non-sharing locks are usually non-sharing for a reason.

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