---
title: "START TRANSACTION"
id: sql-start-transaction
pg_version: "20devel"
---

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# 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
    [ NOT ] DEFERRABLE
```

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## Description

This command begins a new transaction block. If the isolation level, read/write mode, or deferrable mode is specified, the new transaction has those characteristics, as if [`SET TRANSACTION`](sql-set-transaction.md) was executed. This is the same as the [`BEGIN`](sql-begin.md) command. 

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## Parameters

Refer to [SET TRANSACTION](sql-set-transaction.md) for information on the meaning of the parameters to this statement. 

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## 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 `DEFERRABLE` `transaction_mode` is a PostgreSQL language extension. 

The SQL standard requires commas between successive `transaction_modes`, but for historical reasons PostgreSQL allows the commas to be omitted. 

See also the compatibility section of [SET TRANSACTION](sql-set-transaction.md). 

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## See Also

[BEGIN](sql-begin.md), [COMMIT](sql-commit.md), [ROLLBACK](sql-rollback.md), [SAVEPOINT](sql-savepoint.md), [SET TRANSACTION](sql-set-transaction.md)