Mysql Archives - 7-Views

MySQL – UPDATE query with LIMIT

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July 24, 2019

Many a times there are certain conditions where ou want to update your records with certain limit attached to it. To update multiple rows using limit in MySQL can be implement by a query: UPDATE table_name SET field=’1′ WHERE id IN (SELECT id FROM (SELECT id FROM table_name LIMIT 0, 10) tmp);  

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Defragment to Recover Space in MYSQL

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August 24, 2018

If our application is performing a lot of update delete operations on a certain table then there is high possibility that it contains fragmented space. The OPTIMIZE TABLE statement allows MySQL DBAs to reorganize physical table storage in order to achieve three main goals: Shrinks the data pages Shrinks index pages Computes Fresh Index Statistics […]

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Row Level Locking in MySql

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August 22, 2018

We need row level locking to handle the concurrent or simultaneous requests in proper way. MyISAM does not supports row level locking. Why we need row level locking? Suppose two bank clerks attempting to update the same bank account for two different transactions. Clerks 1 and 2 both retrieve (i.e., copy) the account’s record. Clerk […]

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