alter_table man page on Scientific

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       ALTER TABLE - change the definition of a table

       ALTER TABLE [ ONLY ] name [ * ]
	   action [, ... ]
       ALTER TABLE [ ONLY ] name [ * ]
	   RENAME [ COLUMN ] column TO new_column
       ALTER TABLE name
	   RENAME TO new_name
       ALTER TABLE name
	   SET SCHEMA new_schema

       where action is one of:

	   ADD [ COLUMN ] column type [ column_constraint [ ... ] ]
	   ALTER [ COLUMN ] column [ SET DATA ] TYPE type [ USING expression ]
	   ALTER [ COLUMN ] column SET DEFAULT expression
	   ALTER [ COLUMN ] column { SET | DROP } NOT NULL
	   ALTER [ COLUMN ] column SET STATISTICS integer
	   ADD table_constraint
	   DROP CONSTRAINT constraint_name [ RESTRICT | CASCADE ]
	   DISABLE TRIGGER [ trigger_name | ALL | USER ]
	   ENABLE TRIGGER [ trigger_name | ALL | USER ]
	   ENABLE ALWAYS TRIGGER trigger_name
	   DISABLE RULE rewrite_rule_name
	   ENABLE RULE rewrite_rule_name
	   ENABLE REPLICA RULE rewrite_rule_name
	   ENABLE ALWAYS RULE rewrite_rule_name
	   CLUSTER ON index_name
	   SET ( storage_parameter = value [, ... ] )
	   RESET ( storage_parameter [, ... ] )
	   INHERIT parent_table
	   NO INHERIT parent_table
	   OWNER TO new_owner
	   SET TABLESPACE new_tablespace

       ALTER  TABLE  changes  the  definition of an existing table.  There are
       several subforms:

	      This form adds a new column to the table, using the same	syntax
	      as CREATE TABLE [create_table(7)].

	      This  form  drops	 a column from a table. Indexes and table con‐
	      straints involving the column will be automatically  dropped  as
	      well. You will need to say CASCADE if anything outside the table
	      depends on the column, for example, foreign  key	references  or

	      This  form  changes the type of a column of a table. Indexes and
	      simple table constraints involving the column will be  automati‐
	      cally  converted	to  use	 the  new column type by reparsing the
	      originally supplied expression. The optional USING clause speci‐
	      fies  how to compute the new column value from the old; if omit‐
	      ted, the default conversion is the same as  an  assignment  cast
	      from  old	 data  type to new. A USING clause must be provided if
	      there is no implicit or assignment cast from old to new type.

	      These forms set or remove the default value for a	 column.   The
	      default values only apply to subsequent INSERT commands; they do
	      not cause rows already in the table  to  change.	 Defaults  can
	      also  be created for views, in which case they are inserted into
	      INSERT statements on the view before the view's ON  INSERT  rule
	      is applied.

	      These forms change whether a column is marked to allow null val‐
	      ues or to reject null values. You can only use SET NOT NULL when
	      the column contains no null values.

	      This  form  sets	the per-column statistics-gathering target for
	      subsequent ANALYZE [analyze(7)] operations.  The target  can  be
	      set  in  the  range  0  to 10000; alternatively, set it to -1 to
	      revert  to  using	  the	system	 default   statistics	target
	      (default_statistics_target).  For more information on the use of
	      statistics by the PostgreSQL query planner, refer to in the doc‐

	      This  form  sets	the  storage  mode for a column. This controls
	      whether this column is held inline or in a secondary  TOAST  ta‐
	      ble,  and	 whether  the  data should be compressed or not. PLAIN
	      must be used for fixed-length values  such  as  integer  and  is
	      inline,  uncompressed.  MAIN  is	for inline, compressible data.
	      EXTERNAL is for external, uncompressed data, and EXTENDED is for
	      external, compressed data. EXTENDED is the default for most data
	      types that support non-PLAIN storage.  Use of EXTERNAL will make
	      substring	 operations  on	 very  large text and bytea values run
	      faster, at the penalty of increased storage space. Note that SET
	      STORAGE  doesn't	itself	change	anything in the table, it just
	      sets the strategy to be pursued  during  future  table  updates.
	      See in the documentation for more information.

       ADD table_constraint
	      This form adds a new constraint to a table using the same syntax
	      as CREATE TABLE [create_table(7)].

	      This form drops the specified constraint on a table.

	      These forms configure the firing of trigger(s) belonging to  the
	      table.   A disabled trigger is still known to the system, but is
	      not executed when its triggering event occurs.  For  a  deferred
	      trigger, the enable status is checked when the event occurs, not
	      when the trigger function is actually executed. One can  disable
	      or enable a single trigger specified by name, or all triggers on
	      the table, or only user triggers (this option excludes  triggers
	      that  are	 used to implement foreign key constraints). Disabling
	      or enabling constraint triggers requires	superuser  privileges;
	      it  should be done with caution since of course the integrity of
	      the constraint cannot be guaranteed if the triggers are not exe‐
	      cuted.   The  trigger  firing  mechanism is also affected by the
	      configuration variable session_replication_role. Simply  enabled
	      triggers	will fire when the replication role is ``origin'' (the
	      default) or ``local''. Triggers  configured  as  ENABLE  REPLICA
	      will  only fire if the session is in ``replica'' mode, and trig‐
	      gers configured as ENABLE ALWAYS will  fire  regardless  of  the
	      current replication mode.

	      These  forms  configure the firing of rewrite rules belonging to
	      the table.  A disabled rule is still known to the system, but is
	      not  applied  during  query  rewriting. The semantics are as for
	      disabled/enabled triggers. This configuration is ignored for  ON
	      SELECT  rules,  which  are always applied in order to keep views
	      working even if the current session is in a non-default replica‐
	      tion role.

	      This  form  selects  the default index for future CLUSTER [clus‐
	      ter(7)] operations. It does not actually re-cluster the table.

	      This form removes the most recently  used	 CLUSTER  [cluster(7)]
	      index  specification from the table. This affects future cluster
	      operations that don't specify an index.

	      This form adds an oid system column to the  table	 (see  in  the
	      documentation).  It does nothing if the table already has OIDs.

	      Note  that  this	is  not equivalent to ADD COLUMN oid oid; that
	      would add a normal column that happened to be named oid,	not  a
	      system column.

	      This  form removes the oid system column from the table. This is
	      exactly equivalent to DROP COLUMN oid RESTRICT, except  that  it
	      will not complain if there is already no oid column.

       SET ( storage_parameter = value [, ... ] )
	      This  form changes one or more storage parameters for the table.
	      See Storage Parameters  [create_table(7)]	 for  details  on  the
	      available	 parameters.  Note that the table contents will not be
	      modified immediately by this command; depending on the parameter
	      you  might need to rewrite the table to get the desired effects.
	      That can be done with CLUSTER [cluster(7)] or one of  the	 forms
	      of ALTER TABLE that forces a table rewrite.

	      Note: While CREATE TABLE allows OIDS to be specified in the WITH
	      (storage_parameter) syntax, ALTER TABLE does not treat OIDS as a
	      storage parameter. Instead use the SET WITH OIDS and SET WITHOUT
	      OIDS forms to change OID status.

       RESET ( storage_parameter [, ... ] )
	      This form	 resets	 one  or  more	storage	 parameters  to	 their
	      defaults. As with SET, a table rewrite might be needed to update
	      the table entirely.

       INHERIT parent_table
	      This form adds the target table as a new child of the  specified
	      parent  table.  Subsequently,  queries  against  the parent will
	      include records of the target table. To be added as a child, the
	      target  table  must  already contain all the same columns as the
	      parent (it could have additional columns, too). The columns must
	      have  matching data types, and if they have NOT NULL constraints
	      in the parent then they must also have NOT NULL  constraints  in
	      the child.

	      There  must  also	 be  matching  child-table constraints for all
	      CHECK constraints of the parent. Currently UNIQUE, PRIMARY  KEY,
	      and  FOREIGN  KEY constraints are not considered, but this might
	      change in the future.

       NO INHERIT parent_table
	      This form removes the target table from the list of children  of
	      the  specified  parent  table.  Queries against the parent table
	      will no longer include records drawn from the target table.

       OWNER  This form changes the owner of the table, sequence, or  view  to
	      the specified user.

	      This  form  changes  the	table's	 tablespace  to	 the specified
	      tablespace and moves the data file(s) associated with the	 table
	      to  the  new  tablespace.	 Indexes on the table, if any, are not
	      moved; but they can be  moved  separately	 with  additional  SET
	      TABLESPACE   commands.	See   also   CREATE  TABLESPACE	 [cre‐

       RENAME The RENAME forms change the  name	 of  a	table  (or  an	index,
	      sequence,	 or view) or the name of an individual column in a ta‐
	      ble. There is no effect on the stored data.

	      This form	 moves	the  table  into  another  schema.  Associated
	      indexes,	constraints,  and sequences owned by table columns are
	      moved as well.

       All the actions except RENAME and SET SCHEMA can	 be  combined  into  a
       list  of	 multiple alterations to apply in parallel. For example, it is
       possible to add several columns and/or alter the type of	 several  col‐
       umns  in	 a  single  command.  This  is	particularly useful with large
       tables, since only one pass over the table need be made.

       You must own the table to use ALTER TABLE.  To change the schema	 of  a
       table,  you  must also have CREATE privilege on the new schema.	To add
       the table as a new child of a parent table, you must own the parent ta‐
       ble as well.  To alter the owner, you must also be a direct or indirect
       member of the new owning role, and that role must have CREATE privilege
       on  the	table's	 schema. (These restrictions enforce that altering the
       owner doesn't do anything you couldn't do by  dropping  and  recreating
       the  table.  However, a superuser can alter ownership of any table any‐

       name   The name (optionally schema-qualified) of an existing  table  to
	      alter. If ONLY is specified before the table name, only that ta‐
	      ble is altered. If ONLY is not specified, the table and all  its
	      descendant  tables  (if  any)  are altered. Optionally, * can be
	      specified after the  table  name	to  explicitly	indicate  that
	      descendant tables are included.

       column Name of a new or existing column.

	      New name for an existing column.

	      New name for the table.

       type   Data  type  of  the new column, or new data type for an existing

	      New table constraint for the table.

	      Name of an existing constraint to drop.

	      Automatically drop objects that depend on the dropped column  or
	      constraint (for example, views referencing the column).

	      Refuse  to drop the column or constraint if there are any depen‐
	      dent objects. This is the default behavior.

	      Name of a single trigger to disable or enable.

       ALL    Disable or enable all triggers belonging to  the	table.	 (This
	      requires superuser privilege if any of the triggers are for for‐
	      eign key constraints.)

       USER   Disable or enable all triggers belonging to the table except for
	      foreign key constraint triggers.

	      The  index name on which the table should be marked for cluster‐

	      The name of a table storage parameter.

       value  The new value for a table storage parameter.  This  might	 be  a
	      number or a word depending on the parameter.

	      A parent table to associate or de-associate with this table.

	      The user name of the new owner of the table.

	      The name of the tablespace to which the table will be moved.

	      The name of the schema to which the table will be moved.

       The key word COLUMN is noise and can be omitted.

       When  a column is added with ADD COLUMN, all existing rows in the table
       are initialized with the column's default value	(NULL  if  no  DEFAULT
       clause is specified).

       Adding  a  column  with	a  non-null default or changing the type of an
       existing column will require the entire table  to  be  rewritten.  This
       might  take a significant amount of time for a large table; and it will
       temporarily require double the disk space. Adding or removing a	system
       oid column likewise requires rewriting the entire table.

       Adding  a  CHECK	 or NOT NULL constraint requires scanning the table to
       verify that existing rows meet the constraint.

       The main reason for providing the option to specify multiple changes in
       a  single  ALTER	 TABLE	is  that  multiple table scans or rewrites can
       thereby be combined into a single pass over the table.

       The DROP COLUMN form does not physically remove the column, but	simply
       makes  it  invisible  to	 SQL  operations. Subsequent insert and update
       operations in the table will store a null value for the	column.	 Thus,
       dropping	 a  column is quick but it will not immediately reduce the on-
       disk size of your table, as the space occupied by the dropped column is
       not  reclaimed.	The space will be reclaimed over time as existing rows
       are updated. (These statements do not apply when	 dropping  the	system
       oid column; that is done with an immediate rewrite.)

       The  fact  that	ALTER TYPE requires rewriting the whole table is some‐
       times an advantage, because the rewriting process eliminates  any  dead
       space  in  the  table.  For example, to reclaim the space occupied by a
       dropped column immediately, the fastest way is:

       ALTER TABLE table ALTER COLUMN anycol TYPE anytype;

       where anycol is any remaining table column and anytype is the same type
       that  column  already  has.   This  results  in no semantically-visible
       change in the table, but the command forces rewriting, which  gets  rid
       of no-longer-useful data.

       The  USING  option  of  ALTER  TYPE can actually specify any expression
       involving the old values of the row; that is, it	 can  refer  to	 other
       columns	as  well  as the one being converted. This allows very general
       conversions to be done with the ALTER  TYPE  syntax.  Because  of  this
       flexibility,  the  USING	 expression  is	 not  applied  to the column's
       default value (if any); the result might not be a  constant  expression
       as  required  for a default.  This means that when there is no implicit
       or assignment cast from old to new type, ALTER TYPE might fail to  con‐
       vert the default even though a USING clause is supplied. In such cases,
       drop the default with DROP DEFAULT, perform the ALTER  TYPE,  and  then
       use  SET	 DEFAULT to add a suitable new default. Similar considerations
       apply to indexes and constraints involving the column.

       If a table has any descendant tables,  it  is  not  permitted  to  add,
       rename,	or  change  the	 type  of a column in the parent table without
       doing the same to the descendants. That is, ALTER TABLE	ONLY  will  be
       rejected.  This ensures that the descendants always have columns match‐
       ing the parent.

       A recursive DROP COLUMN operation will remove a descendant table's col‐
       umn  only if the descendant does not inherit that column from any other
       parents and never had an independent definition of the column. A nonre‐
       cursive	DROP  COLUMN  (i.e.,  ALTER  TABLE ONLY ... DROP COLUMN) never
       removes any descendant columns, but instead marks them as independently
       defined rather than inherited.

       The  TRIGGER,  CLUSTER,	OWNER, and TABLESPACE actions never recurse to
       descendant tables; that is, they always act as though ONLY were	speci‐
       fied.   Adding a constraint can recurse only for CHECK constraints, and
       is required to do so for such constraints.

       Changing any part of a system catalog table is not permitted.

       Refer to CREATE TABLE [create_table(7)] for a  further  description  of
       valid  parameters.  in  the  documentation  has	further information on

       To add a column of type varchar to a table:

       ALTER TABLE distributors ADD COLUMN address varchar(30);

       To drop a column from a table:

       ALTER TABLE distributors DROP COLUMN address RESTRICT;

       To change the types of two existing columns in one operation:

       ALTER TABLE distributors
	   ALTER COLUMN address TYPE varchar(80),
	   ALTER COLUMN name TYPE varchar(100);

       To change an integer column containing  UNIX  timestamps	 to  timestamp
       with time zone via a USING clause:

       ALTER TABLE foo
	   ALTER COLUMN foo_timestamp SET DATA TYPE timestamp with time zone
	       timestamp with time zone 'epoch' + foo_timestamp * interval '1 second';

       The same, when the column has a default expression that won't automati‐
       cally cast to the new data type:

       ALTER TABLE foo
	   ALTER COLUMN foo_timestamp DROP DEFAULT,
	   ALTER COLUMN foo_timestamp TYPE timestamp with time zone
	       timestamp with time zone 'epoch' + foo_timestamp * interval '1 second',
	   ALTER COLUMN foo_timestamp SET DEFAULT now();

       To rename an existing column:

       ALTER TABLE distributors RENAME COLUMN address TO city;

       To rename an existing table:

       ALTER TABLE distributors RENAME TO suppliers;

       To add a not-null constraint to a column:

       ALTER TABLE distributors ALTER COLUMN street SET NOT NULL;

       To remove a not-null constraint from a column:

       ALTER TABLE distributors ALTER COLUMN street DROP NOT NULL;

       To add a check constraint to a table and all its children:

       ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5);

       To remove a check constraint from a table and all its children:

       ALTER TABLE distributors DROP CONSTRAINT zipchk;

       To remove a check constraint from one table only:

       ALTER TABLE ONLY distributors DROP CONSTRAINT zipchk;

       (The check constraint remains in place for any child tables.)

       To add a foreign key constraint to a table:

       ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses (address) MATCH FULL;

       To add a (multicolumn) unique constraint to a table:

       ALTER TABLE distributors ADD CONSTRAINT dist_id_zipcode_key UNIQUE (dist_id, zipcode);

       To add an automatically named primary key constraint to a table, noting
       that a table can only ever have one primary key:

       ALTER TABLE distributors ADD PRIMARY KEY (dist_id);

       To move a table to a different tablespace:

       ALTER TABLE distributors SET TABLESPACE fasttablespace;

       To move a table to a different schema:

       ALTER TABLE myschema.distributors SET SCHEMA yourschema;

       The  forms  ADD,	 DROP,	SET DEFAULT, and SET DATA TYPE (without USING)
       conform with the SQL standard. The other forms  are  PostgreSQL	exten‐
       sions  of the SQL standard.  Also, the ability to specify more than one
       manipulation in a single ALTER TABLE command is an extension.

       ALTER TABLE DROP COLUMN can be used to drop the only column of a table,
       leaving	a zero-column table. This is an extension of SQL, which disal‐
       lows zero-column tables.

SQL - Language Statements	  2013-10-08			ALTER TABLE(7)

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