1UPDATE(7) SQL Commands UPDATE(7)
2
6 UPDATE - update rows of a table
7
10 UPDATE [ ONLY ] table [ [ AS ] alias ]
11 SET { column = { expression | DEFAULT } |
12 ( column [, ...] ) = ( { expression | DEFAULT } [, ...] ) } [, ...]
13 [ FROM fromlist ]
14 [ WHERE condition | WHERE CURRENT OF cursor_name ]
15 [ RETURNING * | output_expression [ [ AS ] output_name ] [, ...] ]
16
19 UPDATE changes the values of the specified columns in all rows that
20 satisfy the condition. Only the columns to be modified need be men‐
21 tioned in the SET clause; columns not explicitly modified retain their
22 previous values.
23 By default, UPDATE will update rows in the specified table and all its
25 subtables. If you wish to only update the specific table mentioned, you
26 must use the ONLY clause.
27 There are two ways to modify a table using information contained in
29 other tables in the database: using sub-selects, or specifying addi‐
30 tional tables in the FROM clause. Which technique is more appropriate
31 depends on the specific circumstances.
32 The optional RETURNING clause causes UPDATE to compute and return
34 value(s) based on each row actually updated. Any expression using the
35 table's columns, and/or columns of other tables mentioned in FROM, can
36 be computed. The new (post-update) values of the table's columns are
37 used. The syntax of the RETURNING list is identical to that of the
38 output list of SELECT.
39 You must have the UPDATE privilege on the table, or at least on the
41 column(s) that are listed to be updated. You must also have the SELECT
42 privilege on any column whose values are read in the expressions or
43 condition.
44
46 table The name (optionally schema-qualified) of the table to update.
47 alias A substitute name for the target table. When an alias is pro‐
49 vided, it completely hides the actual name of the table. For
50 example, given UPDATE foo AS f, the remainder of the UPDATE
51 statement must refer to this table as f not foo.
52 column The name of a column in table. The column name can be qualified
54 with a subfield name or array subscript, if needed. Do not
55 include the table's name in the specification of a target column
56 — for example, UPDATE tab SET tab.col = 1 is invalid.
57 expression
59 An expression to assign to the column. The expression can use
60 the old values of this and other columns in the table.
61 DEFAULT
63 Set the column to its default value (which will be NULL if no
64 specific default expression has been assigned to it).
65 fromlist
67 A list of table expressions, allowing columns from other tables
68 to appear in the WHERE condition and the update expressions.
69 This is similar to the list of tables that can be specified in
70 the FROM Clause [select(7)] of a SELECT statement. Note that the
71 target table must not appear in the fromlist, unless you intend
72 a self-join (in which case it must appear with an alias in the
73 fromlist).
74 condition
76 An expression that returns a value of type boolean. Only rows
77 for which this expression returns true will be updated.
78 cursor_name
80 The name of the cursor to use in a WHERE CURRENT OF condition.
81 The row to be updated is the one most recently fetched from this
82 cursor. The cursor must be a non-grouping query on the UPDATE's
83 target table. Note that WHERE CURRENT OF cannot be specified
84 together with a Boolean condition. See DECLARE [declare(7)] for
85 more information about using cursors with WHERE CURRENT OF.
86 output_expression
88 An expression to be computed and returned by the UPDATE command
89 after each row is updated. The expression can use any column
90 names of the table or table(s) listed in FROM. Write * to
91 return all columns.
92 output_name
94 A name to use for a returned column.
95
97 On successful completion, an UPDATE command returns a command tag of
98 the form
99 UPDATE count
101 The count is the number of rows updated. If count is 0, no rows matched
103 the condition (this is not considered an error).
104 If the UPDATE command contains a RETURNING clause, the result will be
106 similar to that of a SELECT statement containing the columns and values
107 defined in the RETURNING list, computed over the row(s) updated by the
108 command.
109
111 When a FROM clause is present, what essentially happens is that the
112 target table is joined to the tables mentioned in the fromlist, and
113 each output row of the join represents an update operation for the tar‐
114 get table. When using FROM you should ensure that the join produces at
115 most one output row for each row to be modified. In other words, a tar‐
116 get row shouldn't join to more than one row from the other table(s). If
117 it does, then only one of the join rows will be used to update the tar‐
118 get row, but which one will be used is not readily predictable.
119 Because of this indeterminacy, referencing other tables only within
121 sub-selects is safer, though often harder to read and slower than using
122 a join.
123
125 Change the word Drama to Dramatic in the column kind of the table
126 films:
127 UPDATE films SET kind = 'Dramatic' WHERE kind = 'Drama';
129 Adjust temperature entries and reset precipitation to its default value
132 in one row of the table weather:
133 UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
135 WHERE city = 'San Francisco' AND date = '2003-07-03';
136 Perform the same operation and return the updated entries:
139 UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
141 WHERE city = 'San Francisco' AND date = '2003-07-03'
142 RETURNING temp_lo, temp_hi, prcp;
143 Use the alternative column-list syntax to do the same update:
146 UPDATE weather SET (temp_lo, temp_hi, prcp) = (temp_lo+1, temp_lo+15, DEFAULT)
148 WHERE city = 'San Francisco' AND date = '2003-07-03';
149 Increment the sales count of the salesperson who manages the account
152 for Acme Corporation, using the FROM clause syntax:
153 UPDATE employees SET sales_count = sales_count + 1 FROM accounts
155 WHERE accounts.name = 'Acme Corporation'
156 AND employees.id = accounts.sales_person;
157 Perform the same operation, using a sub-select in the WHERE clause:
160 UPDATE employees SET sales_count = sales_count + 1 WHERE id =
162 (SELECT sales_person FROM accounts WHERE name = 'Acme Corporation');
163 Attempt to insert a new stock item along with the quantity of stock. If
166 the item already exists, instead update the stock count of the existing
167 item. To do this without failing the entire transaction, use save‐
168 points:
169 BEGIN;
171 -- other operations
172 SAVEPOINT sp1;
173 INSERT INTO wines VALUES('Chateau Lafite 2003', '24');
174 -- Assume the above fails because of a unique key violation,
175 -- so now we issue these commands:
176 ROLLBACK TO sp1;
177 UPDATE wines SET stock = stock + 24 WHERE winename = 'Chateau Lafite 2003';
178 -- continue with other operations, and eventually
179 COMMIT;
180 Change the kind column of the table films in the row on which the cur‐
183 sor c_films is currently positioned:
184 UPDATE films SET kind = 'Dramatic' WHERE CURRENT OF c_films;
186
189 This command conforms to the SQL standard, except that the FROM and
190 RETURNING clauses are PostgreSQL extensions.
191 According to the standard, the column-list syntax should allow a list
193 of columns to be assigned from a single row-valued expression, such as
194 a sub-select:
195 UPDATE accounts SET (contact_last_name, contact_first_name) =
197 (SELECT last_name, first_name FROM salesmen
198 WHERE salesmen.id = accounts.sales_id);
199 This is not currently implemented — the source must be a list of inde‐
201 pendent expressions.
202 Some other database systems offer a FROM option in which the target ta‐
204 ble is supposed to be listed again within FROM. That is not how Post‐
205 greSQL interprets FROM. Be careful when porting applications that use
206 this extension.
207SQL - Language Statements 2011-09-22 UPDATE(7)