VALUES¶
Function¶
VALUES computes a row or a set of rows based on given values. It is most commonly used to generate a constant table within a large command.
Precautions¶
VALUES lists with 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. In this case, VALUE can handle larger lists than are practical in other contexts.
If more than one row is specified, all the rows must have the same number of elements.
Syntax¶
VALUES {( expression [, ...] )} [, ...]
[ ORDER BY { sort_expression [ ASC | DESC | USING operator ] } [, ...] ]
[ { [ LIMIT { count | ALL } ] [ OFFSET start [ ROW | ROWS ] ] } | { LIMIT start, { count | ALL } } ]
[ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ];
Parameter Description¶
expression
Specifies a constant or expression to compute and insert at the indicated place in the resulting table or set of rows.
In a VALUES list appearing at the top level of an INSERT, an expression can be replaced by DEFAULT to indicate that the destination column's default value should be inserted. DEFAULT cannot be used when VALUES appears in other contexts.
sort_expression
Specifies an expression or integer constant indicating how to sort the result rows.
ASC
Indicates ascending sort order.
DESC
Indicates descending sort order.
operator
Specifies a sorting operator.
count
Specifies the maximum number of rows to return.
start
Specifies the number of rows to skip before starting to return rows.
FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY
The FETCH clause restricts the total number of rows starting from the first row of the return query result, and the default value of count is 1.
Examples¶
Create the reason_t1 table.
CREATE TABLE reason_t1
(
TABLE_SK INTEGER ,
TABLE_ID VARCHAR(20) ,
TABLE_NA VARCHAR(20)
);
Insert a record into a table.
INSERT INTO reason_t1(TABLE_SK, TABLE_ID, TABLE_NA) VALUES (1, 'S01', 'StudentA');
Insert a record into a table. This command is equivalent to the last one.
INSERT INTO reason_t1 VALUES (1, 'S01', 'StudentA');
Insert records whose TABLE_SK is less than 1 into the table.
INSERT INTO reason_t1 SELECT * FROM reason_t1 WHERE TABLE_SK < 1;
Insert multiple records into a table.
INSERT INTO reason_t1 VALUES (1, 'S01', 'StudentA'),(2, 'T01', 'TeacherA'),(3, 'T02', 'TeacherB');
SELECT * FROM reason_t1 ORDER BY 1;
TABLE_SK | TABLE_ID | TABLE_NAME
----------+----------+------------
1 | S01 | StudentA
2 | T01 | TeacherA
3 | T02 | TeacherB
(3 rows)
Use INSERT OVERWRITE to update data in a table, that is, insert data to overwrite the old data.
INSERT OVERWRITE INTO reason_t1 values (4, 'S02', 'StudentB');
SELECT * FROM reason_t1 ORDER BY 1;
TABLE_SK | TABLE_ID | TABLE_NAME
----------+----------+------------
4 | S02 | StudentB
(1 rows)
Insert data back into the reason_t1 table.
INSERT INTO reason_t1 SELECT * FROM reason_t1;
Specify default values for independent columns.
INSERT INTO reason_t1 VALUES (5, 'S03', DEFAULT);
Insert some data in a table to another table: Use the WITH subquery to obtain a temporary table temp_t, and then insert all data in temp_t to another table reason_t1.
WITH temp_t AS (SELECT * FROM reason_t1) INSERT INTO reason_t1 SELECT * FROM temp_t ORDER BY 1;