SET — change a run-time parameter
SET [ SESSION | LOCAL ]configuration_parameter{ TO | = } {value| 'value' | DEFAULT } SET [ SESSION | LOCAL ] TIME ZONE {value| 'value' | LOCAL | DEFAULT }
   The SET command changes run-time configuration
   parameters.  Many of the run-time parameters listed in
   Chapter 20 can be changed on-the-fly with
   SET.
   (But some require superuser privileges to change, and others 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),
   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.
  
    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.
   
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_parameterName of a settable run-time parameter. Available parameters are documented in Chapter 20 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 20, there are a few that can only be
   adjusted using the SET command or that have a
   special syntax:
   
SCHEMASET SCHEMA ' is an alias for
       value'SET search_path TO .  Only one
       schema can be specified using this syntax.
      value
NAMESSET NAMES  is an alias for
       valueSET 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 ZONESET TIME ZONE ' is an alias
       for value'SET timezone TO '.  The
       syntax value'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.
-7The time zone 7 hours west from UTC (equivalent to PDT). Positive values are east from UTC.
INTERVAL '-08:00' HOUR TO MINUTEThe time zone 8 hours west from UTC (equivalent to PST).
LOCALDEFAULT
           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 for more information
       about time zones.
      
   The function set_config provides equivalent
   functionality; see Section 9.27.1.
   Also, it is possible to UPDATE the
   pg_settings
   system view to perform the equivalent of SET.
  
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';
   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.