FETCH — retrieve rows from a query using a cursor
direction[ FROM | IN ] ]
directioncan be empty or one of: NEXT PRIOR FIRST LAST ABSOLUTE
countALL FORWARD FORWARD
countFORWARD ALL BACKWARD BACKWARD
FETCH retrieves rows using a
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.
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
ALL will always leave the cursor positioned after the last
row or before the first row.
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
The forms using
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
exceeds the number of rows available).
FORWARD 0, and
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.
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 Section 42.7.3.
direction defines the
fetch direction and number of rows to fetch. It can be one of the
Fetch the next row. This is the default if
direction is omitted.
Fetch the prior row.
Fetch the first row of the query (same as
Fetch the last row of the query (same as
of the query, or the
abs('th row from the end
count is negative.
Position before first row or after last row if
count is out of range; in
ABSOLUTE 0 positions
before the first row.
succeeding row, or the
abs('th prior row if
count is negative.
RELATIVE 0 re-fetches the current row,
Fetch the next
rows (same as
Fetch all remaining rows (same as
Fetch the next row (same as
Fetch the next
FORWARD 0 re-fetches the current
Fetch all remaining rows.
Fetch the prior row (same as
Fetch the prior
rows (scanning backwards).
re-fetches the current row.
Fetch all prior rows (scanning backwards).
count is a
possibly-signed integer constant, determining the location or
number of rows to fetch. For
BACKWARD cases, specifying a
equivalent to changing the sense of
An open cursor's name.
On successful completion, a
command returns a command tag of the form
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.
The cursor should be declared with the
SCROLL option if one intends to use any variants
FETCH other than
FETCH NEXT or
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
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.
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;
The SQL standard defines
use in embedded SQL only. The variant of
FETCH described here returns the data as if it
SELECT result rather than
placing it in host variables. Other than this point,
FETCH is fully upward-compatible with the SQL
FETCH forms involving
BACKWARD, as well as the forms
FETCH ALL, in which
FORWARD is implicit, are PostgreSQL extensions.
The SQL standard allows only
preceding the cursor name; the option to use
IN, or to leave them out altogether, is an
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