1FETCH(7) PostgreSQL 9.2.24 Documentation FETCH(7)
2
6 FETCH - retrieve rows from a query using a cursor
7
9 FETCH [ direction [ FROM | IN ] ] cursor_name
10 where direction can be empty or one of:
12 NEXT
14 PRIOR
15 FIRST
16 LAST
17 ABSOLUTE count
18 RELATIVE count
19 count
20 ALL
21 FORWARD
22 FORWARD count
23 FORWARD ALL
24 BACKWARD
25 BACKWARD count
26 BACKWARD ALL
27
29 FETCH retrieves rows using a previously-created cursor.
30 A cursor has an associated position, which is used by FETCH. The cursor
32 position can be before the first row of the query result, on any
33 particular row of the result, or after the last row of the result. When
34 created, a cursor is positioned before the first row. After fetching
35 some rows, the cursor is positioned on the row most recently retrieved.
36 If FETCH runs off the end of the available rows then the cursor is left
37 positioned after the last row, or before the first row if fetching
38 backward. FETCH ALL or FETCH BACKWARD ALL will always leave the cursor
39 positioned after the last row or before the first row.
40 The forms NEXT, PRIOR, FIRST, LAST, ABSOLUTE, RELATIVE fetch a single
42 row after moving the cursor appropriately. If there is no such row, an
43 empty result is returned, and the cursor is left positioned before the
44 first row or after the last row as appropriate.
45 The forms using FORWARD and BACKWARD retrieve the indicated number of
47 rows moving in the forward or backward direction, leaving the cursor
48 positioned on the last-returned row (or after/before all rows, if the
49 count exceeds the number of rows available).
50 RELATIVE 0, FORWARD 0, and BACKWARD 0 all request fetching the current
52 row without moving the cursor, that is, re-fetching the most recently
53 fetched row. This will succeed unless the cursor is positioned before
54 the first row or after the last row; in which case, no row is returned.
55 Note
57 This page describes usage of cursors at the SQL command level. If
58 you are trying to use cursors inside a PL/pgSQL function, the rules
59 are different — see Section 39.7, “Cursors”, in the documentation.
60
62 direction
63 direction defines the fetch direction and number of rows to fetch.
64 It can be one of the following:
65 NEXT
67 Fetch the next row. This is the default if direction is
68 omitted.
69 PRIOR
71 Fetch the prior row.
72 FIRST
74 Fetch the first row of the query (same as ABSOLUTE 1).
75 LAST
77 Fetch the last row of the query (same as ABSOLUTE -1).
78 ABSOLUTE count
80 Fetch the count'th row of the query, or the abs(count)'th row
81 from the end if count is negative. Position before first row or
82 after last row if count is out of range; in particular,
83 ABSOLUTE 0 positions before the first row.
84 RELATIVE count
86 Fetch the count'th succeeding row, or the abs(count)'th prior
87 row if count is negative. RELATIVE 0 re-fetches the current
88 row, if any.
89 count
91 Fetch the next count rows (same as FORWARD count).
92 ALL
94 Fetch all remaining rows (same as FORWARD ALL).
95 FORWARD
97 Fetch the next row (same as NEXT).
98 FORWARD count
100 Fetch the next count rows. FORWARD 0 re-fetches the current
101 row.
102 FORWARD ALL
104 Fetch all remaining rows.
105 BACKWARD
107 Fetch the prior row (same as PRIOR).
108 BACKWARD count
110 Fetch the prior count rows (scanning backwards). BACKWARD 0
111 re-fetches the current row.
112 BACKWARD ALL
114 Fetch all prior rows (scanning backwards).
115 count
117 count is a possibly-signed integer constant, determining the
118 location or number of rows to fetch. For FORWARD and BACKWARD
119 cases, specifying a negative count is equivalent to changing the
120 sense of FORWARD and BACKWARD.
121 cursor_name
123 An open cursor's name.
124
126 On successful completion, a FETCH command returns a command tag of the
127 form
128 FETCH count
130 The count is the number of rows fetched (possibly zero). Note that in
132 psql, the command tag will not actually be displayed, since psql
133 displays the fetched rows instead.
134
136 The cursor should be declared with the SCROLL option if one intends to
137 use any variants of FETCH other than FETCH NEXT or FETCH FORWARD with a
138 positive count. For simple queries PostgreSQL will allow backwards
139 fetch from cursors not declared with SCROLL, but this behavior is best
140 not relied on. If the cursor is declared with NO SCROLL, no backward
141 fetches are allowed.
142 ABSOLUTE fetches are not any faster than navigating to the desired row
144 with a relative move: the underlying implementation must traverse all
145 the intermediate rows anyway. Negative absolute fetches are even worse:
146 the query must be read to the end to find the last row, and then
147 traversed backward from there. However, rewinding to the start of the
148 query (as with FETCH ABSOLUTE 0) is fast.
149 DECLARE(7) is used to define a cursor. Use MOVE(7) to change cursor
151 position without retrieving data.
152
154 The following example traverses a table using a cursor:
155 BEGIN WORK;
157 -- Set up a cursor:
159 DECLARE liahona SCROLL CURSOR FOR SELECT * FROM films;
160 -- Fetch the first 5 rows in the cursor liahona:
162 FETCH FORWARD 5 FROM liahona;
163 code | title | did | date_prod | kind | len
165 -------+-------------------------+-----+------------+----------+-------
166 BL101 | The Third Man | 101 | 1949-12-23 | Drama | 01:44
167 BL102 | The African Queen | 101 | 1951-08-11 | Romantic | 01:43
168 JL201 | Une Femme est une Femme | 102 | 1961-03-12 | Romantic | 01:25
169 P_301 | Vertigo | 103 | 1958-11-14 | Action | 02:08
170 P_302 | Becket | 103 | 1964-02-03 | Drama | 02:28
171 -- Fetch the previous row:
173 FETCH PRIOR FROM liahona;
174 code | title | did | date_prod | kind | len
176 -------+---------+-----+------------+--------+-------
177 P_301 | Vertigo | 103 | 1958-11-14 | Action | 02:08
178 -- Close the cursor and end the transaction:
180 CLOSE liahona;
181 COMMIT WORK;
182
184 The SQL standard defines FETCH for use in embedded SQL only. The
185 variant of FETCH described here returns the data as if it were a SELECT
186 result rather than placing it in host variables. Other than this point,
187 FETCH is fully upward-compatible with the SQL standard.
188 The FETCH forms involving FORWARD and BACKWARD, as well as the forms
190 FETCH count and FETCH ALL, in which FORWARD is implicit, are PostgreSQL
191 extensions.
192 The SQL standard allows only FROM preceding the cursor name; the option
194 to use IN, or to leave them out altogether, is an extension.
195
197 CLOSE(7), DECLARE(7), MOVE(7)
198PostgreSQL 9.2.24 2017-11-06 FETCH(7)