# mysql.begin

## Function

Opens a MySQL transaction and returns the `MysqlTransaction` transaction handle.

## Syntax

```bt
tx = mysql(dsn).begin()
```

## Parameters

No parameters. DSN provided by `mysql(dsn)`.

## Return value

| Type | Description |
| ------ | ------ |
| MysqlTransaction | Transaction handle. Query, bind, all, one, exec, commit, rollback, close and status can continue to be called within the transaction. |

## Code Example

```bt
db = mysql('mysql://user:pass@127.0.0.1/test')
tx = db.begin()
ret = tx.query('insert into user(name) values (?)').bind('BT').exec()
tx.commit()
result = ret.rows_affected

// Example output: 1
echo(result)
```

## Notes

- begin will exclusively occupy a connection, do not hold it for a long time until the transaction ends.
- Commit, rollback, or close must be explicitly called after the transaction is completed.
- begin, intra-transaction SQL and commit/rollback/close are all subject to `BT_MYSQL_QUERY_TIMEOUT_MS`.
- When the transaction slow call exceeds `BT_MYSQL_SLOW_MS`, only the time consumption, method name and binding number are recorded, but the binding value is not recorded.