32 lines
1.4 KiB
PHP
32 lines
1.4 KiB
PHP
<?php ?>
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A transaction isolation level sets the default transactional behaviour.
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As the name 'isolation level' suggests, the setting determines how isolated each transation is,
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or what kind of locks are associated with queries inside a transaction.
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The four availible levels are (in ascending order of strictness):
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<br \><br \>
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<i>READ UNCOMMITTED</i>: Barely transactional, this setting allows for so-called 'dirty reads',
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where queries inside one transaction are affected by uncommitted changes in another transaction.
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<br \><br \>
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<i>READ COMMITTED</i>: Committed updates are visible within another transaction.
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This means identical queries within a transaction can return differing results. This is the default in some DBMS's.
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<br \> <br \>
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<i>REPEATABLE READ</i>: Within a transaction, all reads are consistent. This is the default of Mysql INNODB engine.
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<br \><br \>
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<i>SERIALIZABLE</i>: Updates are not permitted in other transactions if a transaction has run an ordinary SELECT query.
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<br \><br \>
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<?php
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renderCode("<?php
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\$tx = \$conn->transaction; // get the transaction module
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// sets the isolation level to READ COMMITTED
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\$tx->setIsolation('READ COMMITTED');
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// sets the isolation level to SERIALIZABLE
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\$tx->setIsolation('SERIALIZABLE');
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// Some drivers (like Mysql) support the fetching of current transaction
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// isolation level. It can be done as follows:
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\$level = \$tx->getIsolation();
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?>");
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?>
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