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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  appropri-
       ately. 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-fetching  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 displayed, 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
       implementation  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 retriev-
       ing 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  FOR-
       WARD 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         2014-02-17                          FETCH(7)