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ALTER TABLE(7)				   SQL Commands 			   ALTER TABLE(7)

       ALTER TABLE - change the definition of a table

       ALTER TABLE [ ONLY ] table [ * ]
	   ADD [ COLUMN ] column type [ column_constraint [ ... ] ]
       ALTER TABLE [ ONLY ] table [ * ]
       ALTER TABLE [ ONLY ] table [ * ]
	   ALTER [ COLUMN ] column { SET DEFAULT value | DROP DEFAULT }
       ALTER TABLE [ ONLY ] table [ * ]
	   ALTER [ COLUMN ] column { SET | DROP } NOT NULL
       ALTER TABLE [ ONLY ] table [ * ]
	   ALTER [ COLUMN ] column SET STATISTICS integer
       ALTER TABLE [ ONLY ] table [ * ]
       ALTER TABLE [ ONLY ] table [ * ]
	   RENAME [ COLUMN ] column TO new_column
       ALTER TABLE table
	   RENAME TO new_table
       ALTER TABLE [ ONLY ] table [ * ]
	   ADD table_constraint
       ALTER TABLE [ ONLY ] table [ * ]
	   DROP CONSTRAINT constraint_name [ RESTRICT | CASCADE ]
       ALTER TABLE table
	   OWNER TO new_owner

       table  The  name  (possibly  schema-qualified)  of  an existing table to alter. If ONLY is
	      specified, only that table is altered. If ONLY is not specified, the table and  all
	      its  descendant tables (if any) are updated. * can be appended to the table name to
	      indicate that descendant tables are to be scanned, but in the current version, this
	      is  the  default behavior. (In releases before 7.1, ONLY was the default behavior.)
	      The default can be altered by changing the SQL_INHERITANCE configuration option.

       column Name of a new or existing column.

       type   Type of the new column.

	      New name for an existing column.

	      New name for the table.

	      New table constraint for the table.

	      Name of an existing constraint to drop.

	      The user name of the new owner of the table.

	      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 dependent objects. This is
	      the default behavior.

	      Message returned from column or table renaming.

       ERROR  Message returned if table or column is not available.

       ALTER TABLE changes the definition of an existing table.  There are several sub-forms:

	      This form adds a new column to the table using the  same	syntax	as  CREATE  TABLE

	      This  form  drops  a  column  from a table. Note that indexes and table constraints
	      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, for-
	      eign key references, views, etc.

	      These forms set or remove the default value for a column. Note that  defaults  only
	      apply to subsequent INSERT commands; they do not cause rows already in the table to
	      change.  Defaults may 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 values or to reject
	      NULL values. You may only SET NOT NULL when the table contains no  null  values  in
	      the column.

	      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  1000;  alterna-
	      tively, set it to -1 to revert to using the system default statistics target.

	      This  form sets the storage mode for a column. This controls whether this column is
	      held inline or in a supplementary table, 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 all data types that support it. The use of EXTERNAL will make substring
	      operations on a TEXT column faster, at the penalty of increased storage space.

       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 table. There is no effect on the stored data.

       ADD table_constraint
	      This form adds a new constraint to a table using the same syntax	as  CREATE  TABLE

	      This  form  drops constraints on a table.  Currently, constraints on tables are not
	      required to have unique names, so there may be more than	one  constraint  matching
	      the specified name. All such constraints will be dropped.

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

       You must own the table to use ALTER TABLE; except for ALTER TABLE OWNER, which may only be
       executed by a superuser.

       The keyword COLUMN is noise and can be omitted.

       In the current implementation of ADD COLUMN, default and NOT NULL clauses for the new col-
       umn are not supported.  The new column always comes into being with all values NULL.   You
       can  use the SET DEFAULT form of ALTER TABLE to set the default afterwards.  (You may also
       want to update  the  already  existing  rows  to  the  new  default  value,  using  UPDATE
       [update(7)].)   If  you	want to mark the column non-null, use the SET NOT NULL form after
       you've entered non-null values for the column in all rows.

       The DROP COLUMN command does not physically remove the column, but simply makes it invisi-
       ble  to	SQL operations. Subsequent inserts and updates of the table will store a NULL 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.	To reclaim the	space  at
       once, do a dummy UPDATE of all rows and then vacuum, as in:

       UPDATE table SET col = col;
       VACUUM FULL table;

       If a table has any descendant tables, it is not permitted to ADD or RENAME 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 matching the parent.

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

       Changing any part of the schema of a system catalog is not permitted.

       Refer to CREATE TABLE for a further description of valid arguments.  The PostgreSQL User's
       Guide has further information on inheritance.

       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 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:

       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 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);

       The  ADD COLUMN form is compliant with the exception that it does not support defaults and
       NOT NULL constraints, as explained above.  The ALTER COLUMN form is in full compliance.

       The clauses to rename tables, columns, indexes, and sequences  are  PostgreSQL  extensions
       from SQL92.

SQL - Language Statements		    2002-11-22				   ALTER TABLE(7)
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