Index for Section 5

Alphabetical listing for F

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FETCH(5)
NAME
  FETCH - retrieve rows from a table using a cursor

SYNOPSIS
  FETCH [ direction ] [ count ] { IN | FROM } cursor
  FETCH [ FORWARD | BACKWARD | RELATIVE ] [ # | ALL | NEXT | PRIOR ] { IN | FROM } cursor

  INPUTS

  direction
       selector defines the fetch direction. It can be one of the following:

       FORWARD
	 fetch next row(s). This is the default if selector is omitted.

       BACKWARD
	 fetch previous row(s).

       RELATIVE
	 Noise word for SQL92 compatibility.

  count
       count determines how many rows to fetch. It can be one of the
       following:

       # A signed integer that specifies how many rows to fetch.  Note that a
	 negative integer is equivalent to changing the sense of FORWARD and
	 BACKWARD.

       ALL
	 Retrieve all remaining rows.

       NEXT
	 Equivalent to specifying a count of 1.

       PRIOR
	 Equivalent to specifying a count of -1.

  cursor
       An open cursor's name.

  OUTPUTS

  FETCH returns the results of the query defined by the specified cursor.
  The following messages will be returned if the query fails:

  NOTICE: PerformPortalFetch: portal "cursor" not found
       If cursor is not previously declared.  The cursor must be declared
       within a transaction block.

  NOTICE: FETCH/ABSOLUTE not supported, using RELATIVE
       PostgreSQL does not support absolute positioning of cursors.

  ERROR: FETCH/RELATIVE at current position is not supported
       SQL92 allows one to repetitively retrieve the cursor at its ``current
       position'' using the syntax

       FETCH RELATIVE 0 FROM cursor.

       PostgreSQL does not currently support this notion; in fact the value
       zero is reserved to indicate that all rows should be retrieved and is
       equivalent to specifying the ALL keyword.  If the RELATIVE keyword has
       been used, PostgreSQL assumes that the user intended SQL92 behavior
       and returns this error message.

DESCRIPTION
  FETCH allows a user to retrieve rows using a cursor.	The number of rows
  retrieved is specified by #.	If the number of rows remaining in the cursor
  is less than #, then only those available are fetched.  Substituting the
  keyword ALL in place of a number will cause all remaining rows in the
  cursor to be retrieved.  Instances may be fetched in both FORWARD and
  BACKWARD directions. The default direction is FORWARD.

       Tip: Negative numbers are allowed to be specified for the row count. A
       negative number is equivalent to reversing the sense of the FORWARD
       and BACKWARD keywords. For example, FORWARD -1 is the same as BACKWARD
       1.

  NOTES

  Note that the FORWARD and BACKWARD keywords are PostgreSQL extensions.  The
  SQL92 syntax is also supported, specified in the second form of the
  command. See below for details on compatibility issues.

  Updating data in a cursor is not supported by PostgreSQL, because mapping
  cursor updates back to base tables is not generally possible, as is also
  the case with VIEW updates.  Consequently, users must issue explicit UPDATE
  commands to replace data.

  Cursors may only be used inside of transactions because the data that they
  store spans multiple user queries.

  Use MOVE [move(5)] to change cursor position.	 DECLARE [declare(5)] will
  define a cursor.  Refer to BEGIN [begin(5)], COMMIT [commit(5)], and
  ROLLBACK [rollback(5)] for further information about transactions.

USAGE
  The following examples traverses a table using a cursor.

  -- Set up and use a cursor:

  BEGIN WORK;
  DECLARE liahona CURSOR FOR SELECT * FROM films;

  -- Fetch first 5 rows in the cursor liahona:
  FETCH FORWARD 5 IN liahona;

   code	 |	    title	   | did | date_prod  |	 kind	 | len
  -------+-------------------------+-----+------------+----------+-------
   BL101 | The Third Man	   | 101 | 1949-12-23 | Drama	 | 01:44
   BL102 | The African Queen	   | 101 | 1951-08-11 | Romantic | 01:43
   JL201 | Une Femme est une Femme | 102 | 1961-03-12 | Romantic | 01:25
   P_301 | Vertigo		   | 103 | 1958-11-14 | Action	 | 02:08
   P_302 | Becket		   | 103 | 1964-02-03 | Drama	 | 02:28

  -- Fetch previous row:
  FETCH BACKWARD 1 IN liahona;

   code	 | title   | did | date_prod  | kind   | len
  -------+---------+-----+------------+--------+-------
   P_301 | Vertigo | 103 | 1958-11-14 | Action | 02:08

  -- close the cursor and commit work:

  CLOSE liahona;
  COMMIT WORK;

COMPATIBILITY
  SQL92

       Note: The non-embedded use of cursors is a PostgreSQL extension. The
       syntax and usage of cursors is being compared against the embedded
       form of cursors defined in SQL92.

  SQL92 allows absolute positioning of the cursor for FETCH, and allows
  placing the results into explicit variables:

  FETCH ABSOLUTE #
      FROM cursor
      INTO :variable [, ...]

  ABSOLUTE
       The cursor should be positioned to the specified absolute row number.
       All row numbers in PostgreSQL are relative numbers so this capability
       is not supported.

  :variable
       Target host variable(s).

Index for Section 5

Alphabetical listing for F

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