> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/reference/sql-commands/sql-start-transaction.md).

# START TRANSACTION

### START TRANSACTION

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
```

### 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`](/reference/sql-commands/sql-set-transaction.md) was executed. This is the same as the [`BEGIN`](/reference/sql-commands/sql-begin.md) command.

### Parameters

Refer to [SET TRANSACTION](/reference/sql-commands/sql-set-transaction.md) 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 `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](/reference/sql-commands/sql-set-transaction.md).

### See Also

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

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/sql-start-transaction.html)（英文原文，待翻譯）


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