FETCH(7)                                                  SQL Commands                                                  FETCH(7)



NAME
       FETCH - retrieve rows from a query using a cursor


SYNOPSIS
       FETCH [ direction { FROM | IN } ] cursorname

       where direction can be empty or one of:

           NEXT
           PRIOR
           FIRST
           LAST
           ABSOLUTE count
           RELATIVE count
           count
           ALL
           FORWARD
           FORWARD count
           FORWARD ALL
           BACKWARD
           BACKWARD count
           BACKWARD ALL


DESCRIPTION
       FETCH retrieves rows using a previously-created cursor.

       A cursor has an associated position, which is used by FETCH. The cursor position can be before the first row of the query
       result, on any particular row of the result, or after the last row of the result. When created, a  cursor  is  positioned
       before  the  first  row.  After fetching some rows, the cursor is positioned on the row most recently retrieved. If FETCH
       runs off the end of the available rows then the cursor is left positioned after the last row, or before the first row  if
       fetching  backward.  FETCH ALL or FETCH BACKWARD ALL will always leave the cursor positioned after the last row or before
       the first row.

       The forms NEXT, PRIOR, FIRST, LAST, ABSOLUTE, RELATIVE fetch a single row after moving the cursor appropriately. If there
       is no such row, an empty result is returned, and the cursor is left positioned before the first row or after the last row
       as appropriate.

       The forms using FORWARD and BACKWARD retrieve the indicated number of rows moving in the forward or  backward  direction,
       leaving the cursor positioned on the last-returned row (or after/before all rows, if the count exceeds the number of rows
       available).

       RELATIVE 0, FORWARD 0, and BACKWARD 0 all request fetching the current row without moving the cursor, that is,  re-fetch-
       ing  the  most  recently fetched row. This will succeed unless the cursor is positioned before the first row or after the
       last row; in which case, no row is returned.

              Note: This page describes usage of cursors at the SQL command level.  If you are trying to use  cursors  inside  a
              PL/pgSQL function, the rules are different -- see in the documentation.


PARAMETERS
       direction
              direction defines the fetch direction and number of rows to fetch. It can be one of the following:

              NEXT   Fetch the next row. This is the default if direction is omitted.

              PRIOR  Fetch the prior row.

              FIRST  Fetch the first row of the query (same as ABSOLUTE 1).

              LAST   Fetch the last row of the query (same as ABSOLUTE -1).

              ABSOLUTE count
                     Fetch  the  count'th row of the query, or the abs(count)'th row from the end if count is negative. Position
                     before first row or after last row if count is out of range; in particular, ABSOLUTE 0 positions before the
                     first row.

              RELATIVE count
                     Fetch  the  count'th  succeeding  row,  or the abs(count)'th prior row if count is negative. RELATIVE 0 re-
                     fetches the current row, if any.

              count  Fetch the next count rows (same as FORWARD count).

              ALL    Fetch all remaining rows (same as FORWARD ALL).

              FORWARD
                     Fetch the next row (same as NEXT).

              FORWARD count
                     Fetch the next count rows.  FORWARD 0 re-fetches the current row.

              FORWARD ALL
                     Fetch all remaining rows.

              BACKWARD
                     Fetch the prior row (same as PRIOR).

              BACKWARD count
                     Fetch the prior count rows (scanning backwards). BACKWARD 0 re-fetches the current row.

              BACKWARD ALL
                     Fetch all prior rows (scanning backwards).

       count  count is a possibly-signed integer constant, determining the location or number of rows to fetch. For FORWARD  and
              BACKWARD cases, specifying a negative count is equivalent to changing the sense of FORWARD and BACKWARD.

       cursorname
              An open cursor's name.

OUTPUTS
       On successful completion, a FETCH command returns a command tag of the form

       FETCH count

       The  count  is  the  number of rows fetched (possibly zero). Note that in psql, the command tag will not actually be dis-
       played, since psql displays the fetched rows instead.

NOTES
       The cursor should be declared with the SCROLL option if one intends to use any variants of FETCH other than FETCH NEXT or
       FETCH  FORWARD  with a positive count. For simple queries PostgreSQL will allow backwards fetch from cursors not declared
       with SCROLL, but this behavior is best not relied on. If the cursor is declared with NO SCROLL, no backward  fetches  are
       allowed.

       ABSOLUTE  fetches  are not any faster than navigating to the desired row with a relative move: the underlying implementa-
       tion must traverse all the intermediate rows anyway.  Negative absolute fetches are even worse: the query must be read to
       the  end  to  find the last row, and then traversed backward from there. However, rewinding to the start of the query (as
       with FETCH ABSOLUTE 0) is fast.

       DECLARE [declare(7)] is used to define a cursor. Use MOVE [move(7)] to change cursor position without retrieving data.

EXAMPLES
       The following example traverses a table using a cursor:

       BEGIN WORK;

       -- Set up a cursor:
       DECLARE liahona SCROLL CURSOR FOR SELECT * FROM films;

       -- Fetch the first 5 rows in the cursor liahona:
       FETCH FORWARD 5 FROM 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 the previous row:
       FETCH PRIOR FROM liahona;

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

       -- Close the cursor and end the transaction:
       CLOSE liahona;
       COMMIT WORK;


COMPATIBILITY
       The SQL standard defines FETCH for use in embedded SQL only. The variant of FETCH described here returns the data  as  if
       it were a SELECT result rather than placing it in host variables. Other than this point, FETCH is fully upward-compatible
       with the SQL standard.

       The FETCH forms involving FORWARD and BACKWARD, as well as the forms FETCH count and  FETCH  ALL,  in  which  FORWARD  is
       implicit, are PostgreSQL extensions.

       The SQL standard allows only FROM preceding the cursor name; the option to use IN is an extension.

SEE ALSO
       CLOSE [close(7)], DECLARE [declare(7)], MOVE [move(7)]



SQL - Language Statements                                  2011-09-22                                                   FETCH(7)