> 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-set.md).
# SET
### SET
SET — change a run-time parameter
### Synopsis
```
SET [ SESSION | LOCAL ] configuration_parameter { TO | = } { value | 'value' | DEFAULT }
SET [ SESSION | LOCAL ] TIME ZONE { value | 'value' | LOCAL | DEFAULT }
```
### Description
The `SET` command changes run-time configuration parameters. Many of the run-time parameters listed in [Chapter 19](/server-administration/runtime-config.md) can be changed on-the-fly with `SET`. (Some parameters can only be changed by superusers and users who have been granted `SET` privilege on that parameter. There are also parameters that cannot be changed after server or session start.) `SET` only affects the value used by the current session.
If `SET` (or equivalently `SET SESSION`) is issued within a transaction that is later aborted, the effects of the `SET` command disappear when the transaction is rolled back. Once the surrounding transaction is committed, the effects will persist until the end of the session, unless overridden by another `SET`.
The effects of `SET LOCAL` last only till the end of the current transaction, whether committed or not. A special case is `SET` followed by `SET LOCAL` within a single transaction: the `SET LOCAL` value will be seen until the end of the transaction, but afterwards (if the transaction is committed) the `SET` value will take effect.
The effects of `SET` or `SET LOCAL` are also canceled by rolling back to a savepoint that is earlier than the command.
If `SET LOCAL` is used within a function that has a `SET` option for the same variable (see [CREATE FUNCTION](/reference/sql-commands/sql-createfunction.md)), the effects of the `SET LOCAL` command disappear at function exit; that is, the value in effect when the function was called is restored anyway. This allows `SET LOCAL` to be used for dynamic or repeated changes of a parameter within a function, while still having the convenience of using the `SET` option to save and restore the caller's value. However, a regular `SET` command overrides any surrounding function's `SET` option; its effects will persist unless rolled back.
#### Note
In PostgreSQL versions 8.0 through 8.2, the effects of a `SET LOCAL` would be canceled by releasing an earlier savepoint, or by successful exit from a PL/pgSQL exception block. This behavior has been changed because it was deemed unintuitive.
### Parameters
`SESSION` : Specifies that the command takes effect for the current session. (This is the default if neither `SESSION` nor `LOCAL` appears.)
`LOCAL` : Specifies that the command takes effect for only the current transaction. After `COMMIT` or `ROLLBACK`, the session-level setting takes effect again. Issuing this outside of a transaction block emits a warning and otherwise has no effect.
*`configuration_parameter`* : Name of a settable run-time parameter. Available parameters are documented in [Chapter 19](/server-administration/runtime-config.md) and below.
*`value`* : New value of parameter. Values can be specified as string constants, identifiers, numbers, or comma-separated lists of these, as appropriate for the particular parameter. `DEFAULT` can be written to specify resetting the parameter to its default value (that is, whatever value it would have had if no `SET` had been executed in the current session).
Besides the configuration parameters documented in [Chapter 19](/server-administration/runtime-config.md), there are a few that can only be adjusted using the `SET` command or that have a special syntax:
`SCHEMA` : `SET SCHEMA 'value'` is an alias for `SET search_path TO value`. Only one schema can be specified using this syntax.
`NAMES` : `SET NAMES 'value'` is an alias for `SET client_encoding TO value`.
`SEED` : Sets the internal seed for the random number generator (the function `random`). Allowed values are floating-point numbers between -1 and 1 inclusive.
````
The seed can also be set by invoking the function
`setseed`:
```
SELECT setseed(value);
```
````
`TIME ZONE` : `SET TIME ZONE 'value'` is an alias for `SET timezone TO 'value'`. The syntax `SET TIME ZONE` allows special syntax for the time zone specification. Here are examples of valid values:
```
`'America/Los_Angeles'`
: The time zone for Berkeley, California.
`'Europe/Rome'`
: The time zone for Italy.
`-7`
: The time zone 7 hours west from UTC (equivalent
to PDT). Positive values are east from UTC.
`INTERVAL '-08:00' HOUR TO MINUTE`
: The time zone 8 hours west from UTC (equivalent
to PST).
`LOCAL`
`DEFAULT`
: Set the time zone to your local time zone (that is, the
server's default value of `timezone`).
Timezone settings given as numbers or intervals are internally
translated to POSIX timezone syntax. For example, after
`SET TIME ZONE -7`, `SHOW TIME ZONE` would
report `<-07>+07`.
Time zone abbreviations are not supported by `SET`;
see [Section 8.5.3](../../the-sql-language/datatype/datatype-datetime.md#DATATYPE-TIMEZONES) for more information
about time zones.
```
### Notes
The function `set_config` provides equivalent functionality; see [Section 9.28.1](/the-sql-language/functions/functions-admin.md#FUNCTIONS-ADMIN-SET). Also, it is possible to UPDATE the [`pg_settings`](/internals/views/view-pg-settings.md) system view to perform the equivalent of `SET`.
### Examples
Set the schema search path:
```
SET search_path TO my_schema, public;
```
Set the style of date to traditional POSTGRES with “day before month” input convention:
```
SET datestyle TO postgres, dmy;
```
Set the time zone for Berkeley, California:
```
SET TIME ZONE 'America/Los_Angeles';
```
Set the time zone for Italy:
```
SET TIME ZONE 'Europe/Rome';
```
### Compatibility
`SET TIME ZONE` extends syntax defined in the SQL standard. The standard allows only numeric time zone offsets while PostgreSQL allows more flexible time-zone specifications. All other `SET` features are PostgreSQL extensions.
### See Also
[RESET](/reference/sql-commands/sql-reset.md), [SHOW](/reference/sql-commands/sql-show.md)
***
原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/sql-set.html)（英文原文，待翻譯）
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