Name
VALUES -- compute a set of rowsSynopsis
VALUES ( expression [, ...] ) [, ...] [ ORDER BY sort_expression [ ASC | DESC | USING operator ] [, ...] ] [ LIMIT { count | ALL } ] [ OFFSET start [ ROW | ROWS ] ] [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ]
Description
VALUES
computes a row value or set of row values specified by value expressions. It is most commonly used to generate a "constant table" within a larger command, but it can be used on its own.
When more than one row is specified, all the rows must have the same number of elements. The data types of the resulting table's columns are determined by combining the explicit or inferred types of the expressions appearing in that column, using the same rules as for UNION
(see Section 10.5).
Within larger commands, VALUES
is syntactically allowed anywhere that SELECT
is. Because it is treated like a SELECT
by the grammar, it is possible to use the ORDER BY
, LIMIT
(or equivalently FETCH FIRST
), and OFFSET
clauses with a VALUES
command.
Parameters
expression
-
A constant or expression to compute and insert at the indicated place in the resulting table (set of rows). In a
VALUES
list appearing at the top level of anINSERT
, anexpression
can be replaced byDEFAULT
to indicate that the destination column's default value should be inserted.DEFAULT
cannot be used whenVALUES
appears in other contexts. sort_expression
-
An expression or integer constant indicating how to sort the result rows. This expression can refer to the columns of the
VALUES
result ascolumn1
,column2
, etc. For more details see ORDER BY Clause. operator
-
A sorting operator. For details see ORDER BY Clause.
count
-
The maximum number of rows to return. For details see LIMIT Clause.
start
-
The number of rows to skip before starting to return rows. For details see LIMIT Clause.
Notes
VALUES
lists with very large numbers of rows should be avoided, as you might encounter out-of-memory failures or poor performance. VALUES
appearing within INSERT
is a special case (because the desired column types are known from the INSERT
's target table, and need not be inferred by scanning the VALUES
list), so it can handle larger lists than are practical in other contexts.
Examples
A bare VALUES
command:
VALUES (1, 'one'), (2, 'two'), (3, 'three');
This will return a table of two columns and three rows. It's effectively equivalent to:
SELECT 1 AS column1, 'one' AS column2 UNION ALL SELECT 2, 'two' UNION ALL SELECT 3, 'three';
More usually, VALUES
is used within a larger SQL command. The most common use is in INSERT
:
INSERT INTO films (code, title, did, date_prod, kind) VALUES ('T_601', 'Yojimbo', 106, '1961-06-16', 'Drama');
In the context of INSERT
, entries of a VALUES
list can be DEFAULT
to indicate that the column default should be used here instead of specifying a value:
INSERT INTO films VALUES ('UA502', 'Bananas', 105, DEFAULT, 'Comedy', '82 minutes'), ('T_601', 'Yojimbo', 106, DEFAULT, 'Drama', DEFAULT);
VALUES
can also be used where a sub-SELECT
might be written, for example in a FROM
clause:
SELECT f.* FROM films f, (VALUES('MGM', 'Horror'), ('UA', 'Sci-Fi')) AS t (studio, kind) WHERE f.studio = t.studio AND f.kind = t.kind; UPDATE employees SET salary = salary * v.increase FROM (VALUES(1, 200000, 1.2), (2, 400000, 1.4)) AS v (depno, target, increase) WHERE employees.depno = v.depno AND employees.sales >= v.target;
Note that an AS
clause is required when VALUES
is used in a FROM
clause, just as is true for SELECT
. It is not required that the AS
clause specify names for all the columns, but it's good practice to do so. (The default column names for VALUES
are column1
, column2
, etc in PostgreSQL, but these names might be different in other database systems.)
When VALUES
is used in INSERT
, the values are all automatically coerced to the data type of the corresponding destination column. When it's used in other contexts, it might be necessary to specify the correct data type. If the entries are all quoted literal constants, coercing the first is sufficient to determine the assumed type for all:
SELECT * FROM machines WHERE ip_address IN (VALUES('192.168.0.1'::inet), ('192.168.0.10'), ('192.168.1.43'));
Tip: For simple
IN
tests, it's better to rely on the list-of-scalars form ofIN
than to write aVALUES
query as shown above. The list of scalars method requires less writing and is often more efficient.
Compatibility
VALUES
conforms to the SQL standard. LIMIT
and OFFSET
are PostgreSQL extensions; see also under SELECT.
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