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start_transaction(7) [opendarwin man page]

START 
TRANSACTION(7) SQL Commands START TRANSACTION(7) NAME
START TRANSACTION - start a transaction block SYNOPSIS
START TRANSACTION [ transaction_mode [, ...] ] where transaction_mode is one of: ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED } READ WRITE | READ ONLY DESCRIPTION
This command begins a new transaction block. If the isolation level or read/write mode is specified, the new transaction has those charac- teristics, as if SET TRANSACTION [set_transaction(7)] was executed. This is the same as the BEGIN [begin(7)] command. PARAMETERS
Refer to SET TRANSACTION [set_transaction(7)] for information on the meaning of the parameters to this statement. COMPATIBILITY
In the standard, it is not necessary to issue START TRANSACTION to start a transaction block: any SQL command implicitly begins a block. PostgreSQL's behavior can be seen as implicitly issuing a COMMIT after each command that does not follow START TRANSACTION (or BEGIN), and it is therefore often called ``autocommit''. Other relational database systems might offer an autocommit feature as a convenience. The SQL standard requires commas between successive transaction_modes, but for historical reasons PostgreSQL allows the commas to be omit- ted. See also the compatibility section of SET TRANSACTION [set_transaction(7)]. SEE ALSO
BEGIN [begin(7)], COMMIT [commit(7)], ROLLBACK [rollback(7)], SAVEPOINT [savepoint(7)], SET TRANSACTION [set_transaction(7)] SQL - Language Statements 2010-05-14 START TRANSACTION(7)

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BEGIN(7)							   SQL Commands 							  BEGIN(7)

NAME
BEGIN - start a transaction block SYNOPSIS
BEGIN [ WORK | TRANSACTION ] [ transaction_mode [, ...] ] where transaction_mode is one of: ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED } READ WRITE | READ ONLY DESCRIPTION
BEGIN initiates a transaction block, that is, all statements after a BEGIN command will be executed in a single transaction until an explicit COMMIT [commit(7)] or ROLLBACK [rollback(7)] is given. By default (without BEGIN), PostgreSQL executes transactions in ``autocom- mit'' mode, that is, each statement is executed in its own transaction and a commit is implicitly performed at the end of the statement (if execution was successful, otherwise a rollback is done). Statements are executed more quickly in a transaction block, because transaction start/commit requires significant CPU and disk activity. Execution of multiple statements inside a transaction is also useful to ensure consistency when making several related changes: other ses- sions will be unable to see the intermediate states wherein not all the related updates have been done. If the isolation level or read/write mode is specified, the new transaction has those characteristics, as if SET TRANSACTION [set_transac- tion(7)] was executed. PARAMETERS
WORK TRANSACTION Optional key words. They have no effect. Refer to SET TRANSACTION [set_transaction(7)] for information on the meaning of the other parameters to this statement. NOTES
START TRANSACTION [start_transaction(7)] has the same functionality as BEGIN. Use COMMIT [commit(7)] or ROLLBACK [rollback(7)] to terminate a transaction block. Issuing BEGIN when already inside a transaction block will provoke a warning message. The state of the transaction is not affected. To nest transactions within a transaction block, use savepoints (see SAVEPOINT [savepoint(7)]). For reasons of backwards compatibility, the commas between successive transaction_modes can be omitted. EXAMPLES
To begin a transaction block: BEGIN; COMPATIBILITY
BEGIN is a PostgreSQL language extension. It is equivalent to the SQL-standard command START TRANSACTION [start_transaction(7)], whose ref- erence page contains additional compatibility information. Incidentally, the BEGIN key word is used for a different purpose in embedded SQL. You are advised to be careful about the transaction semantics when porting database applications. SEE ALSO
COMMIT [commit(7)], ROLLBACK [rollback(7)], START TRANSACTION [start_transaction(7)], SAVEPOINT [savepoint(7)] SQL - Language Statements 2010-05-14 BEGIN(7)
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