UPDATE(7)

📦 version 16.15, in opensuse-leap 16.0

👑 UPDATE 👑

okay so this is UPDATE(7) from the PostgreSQL 16.15 Documentation, and it is literally the main-character command for changing rows in a table. bestie, this one is iconic. 💅

🎀 NAME 🎀

UPDATE — update rows of a table

✨ SYNOPSIS ✨

[ WITH [ RECURSIVE ] with_query [, ...] ]
UPDATE [ ONLY ] table_name [ * ] [ [ AS ] alias ]
    SET { column_name = { expression | DEFAULT } |
          ( column_name [, ...] ) = [ ROW ] ( { expression | DEFAULT } [, ...] ) |
          ( column_name [, ...] ) = ( sub-SELECT )
        } [, ...]
    [ FROM from_item [, ...] ]
    [ WHERE condition | WHERE CURRENT OF cursor_name ]
    [ RETURNING { * | output_expression [ [ AS ] output_name ] } [, ...] ]

💖 DESCRIPTION 💖

UPDATE changes the values of the specified columns in all rows that satisfy the condition. Only the columns to be modified need to be mentioned in the SET clause; columns not explicitly modified retain their previous values. no cap, that part is lowkey important.

There are two ways to modify a table using information contained in other tables in the database: using sub-selects, or specifying additional tables in the FROM clause. Which technique is more appropriate depends on the specific circumstances. it's giving “depends on the vibes and the query plan,” honestly.

The optional RETURNING clause causes UPDATE to compute and return value(s) based on each row actually updated. Any expression using the table's columns, and/or columns of other tables mentioned in FROM, can be computed. The new (post-update) values of the table's columns are used. The syntax of the RETURNING list is identical to that of the output list of SELECT.

You must have the UPDATE privilege on the table, or at least on the column(s) that are listed to be updated. You must also have the SELECT privilege on any column whose values are read in the expressions or condition. permissions check: slay responsibly. 🫶

🌸 PARAMETERS 🌸

  • with_query — The WITH clause lets you specify one or more subqueries that can be referenced by name in the UPDATE query. See Section 7.8 and SELECT(7) for details. very “name it and use it later” energy.
  • table_name — The name (optionally schema-qualified) of the table to update. If ONLY is specified before the table name, matching rows are updated in the named table only. If ONLY is not specified, matching rows are also updated in any tables inheriting from the named table. Optionally, * can be specified after the table name to explicitly indicate that descendant tables are included.
  • alias — A substitute name for the target table. When an alias is provided, it completely hides the actual name of the table. For example, given UPDATE foo AS f, the remainder of the UPDATE statement must refer to this table as f not foo. she said “new name, new me.” 💅
  • column_name — The name of a column in the table named by table_name. The column name can be qualified with a subfield name or array subscript, if needed. Do not include the table's name in the specification of a target column — for example, UPDATE table_name SET table_name.col = 1 is invalid.
  • expression — An expression to assign to the column. The expression can use the old values of this and other columns in the table.
  • DEFAULT — Set the column to its default value (which will be NULL if no specific default expression has been assigned to it). An identity column will be set to a new value generated by the associated sequence. For a generated column, specifying this is permitted but merely specifies the normal behavior of computing the column from its generation expression.
  • sub-SELECT — A SELECT sub-query that produces as many output columns as are listed in the parenthesized column list preceding it. The sub-query must yield no more than one row when executed. If it yields one row, its column values are assigned to the target columns; if it yields no rows, NULL values are assigned to the target columns. The sub-query can refer to old values of the current row of the table being updated. one row max, bestie — do not push it. 😭
  • from_item — A table expression allowing columns from other tables to appear in the WHERE condition and update expressions. This uses the same syntax as the FROM clause of a SELECT statement; for example, an alias for the table name can be specified. Do not repeat the target table as a from_item unless you intend a self-join (in which case it must appear with an alias in the from_item).
  • condition — An expression that returns a value of type boolean. Only rows for which this expression returns true will be updated.
  • cursor_name — The name of the cursor to use in a WHERE CURRENT OF condition. The row to be updated is the one most recently fetched from this cursor. The cursor must be a non-grouping query on the UPDATE's target table. Note that WHERE CURRENT OF cannot be specified together with a Boolean condition. See DECLARE(7) for more information about using cursors with WHERE CURRENT OF.
  • output_expression — An expression to be computed and returned by the UPDATE command after each row is updated. The expression can use any column names of the table named by table_name or table(s) listed in FROM. Write * to return all columns.
  • output_name — A name to use for a returned column.

🦋 OUTPUTS 🦋

On successful completion, an UPDATE command returns a command tag of the form

UPDATE count

The count is the number of rows updated, including matched rows whose values did not change. Note that the number may be less than the number of rows that matched the condition when updates were suppressed by a BEFORE UPDATE trigger. If count is 0, no rows were updated by the query (this is not considered an error). zero rows is not a flop, it's just facts. 💀

If the UPDATE command contains a RETURNING clause, the result will be similar to that of a SELECT statement containing the columns and values defined in the RETURNING list, computed over the row(s) updated by the command.

🔥 NOTES 🔥

When a FROM clause is present, what essentially happens is that the target table is joined to the tables mentioned in the from_item list, and each output row of the join represents an update operation for the target table. When using FROM you should ensure that the join produces at most one output row for each row to be modified. In other words, a target row shouldn't join to more than one row from the other table(s). If it does, then only one of the join rows will be used to update the target row, but which one will be used is not readily predictable. that is highkey a “do not leave this to fate” situation. 🙈

Because of this indeterminacy, referencing other tables only within sub-selects is safer, though often harder to read and slower than using a join.

In the case of a partitioned table, updating a row might cause it to no longer satisfy the partition constraint of the containing partition. In that case, if there is some other partition in the partition tree for which this row satisfies its partition constraint, then the row is moved to that partition. If there is no such partition, an error will occur. Behind the scenes, the row movement is actually a DELETE and INSERT operation. plot twist: the row literally moves out and moves back in. 💅

There is a possibility that a concurrent UPDATE or DELETE on the row being moved will get a serialization failure error. Suppose session 1 is performing an UPDATE on a partition key, and meanwhile a concurrent session 2 for which this row is visible performs an UPDATE or DELETE operation on this row. In such case, session 2's UPDATE or DELETE will detect the row movement and raise a serialization failure error (which always returns with an SQLSTATE code '40001'). Applications may wish to retry the transaction if this occurs. In the usual case where the table is not partitioned, or where there is no row movement, session 2 would have identified the newly updated row and carried out the UPDATE/DELETE on this new row version. so yeah, '40001' is the “bestie, retry the transaction” code. 🔁

Note that while rows can be moved from local partitions to a foreign-table partition (provided the foreign data wrapper supports tuple routing), they cannot be moved from a foreign-table partition to another partition.

An attempt of moving a row from one partition to another will fail if a foreign key is found to directly reference an ancestor of the source partition that is not the same as the ancestor that's mentioned in the UPDATE query.

✨ EXAMPLES ✨

Okay bestie, this is the part where it all comes together. Real queries, real vibes, copy-paste ready 💅

Scenario one: you wanna change the word Drama to Dramatic in the kind column of the table films:

UPDATE films SET kind = 'Dramatic' WHERE kind = 'Drama';

Glow-up complete, no notes ✨

Scenario two: adjust the temperature entries and reset precipitation back to its default value, all in one single row of the table weather:

UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
  WHERE city = 'San Francisco' AND date = '2003-07-03';

One row, three changes, zero drama. Efficiency icon 🎀

Scenario three: same operation as above, but this time you want the updated entries handed back to you:

UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT
  WHERE city = 'San Francisco' AND date = '2003-07-03'
  RETURNING temp_lo, temp_hi, prcp;

Like, why guess when the database will literally show you 👑

Scenario four: same update again, but using the alternative column-list syntax this time:

UPDATE weather SET (temp_lo, temp_hi, prcp) = (temp_lo+1, temp_lo+15, DEFAULT)
  WHERE city = 'San Francisco' AND date = '2003-07-03';

Grouping the columns on the left and the values on the right — it's giving organized, it's giving put-together 🦋

Scenario five: bump the sales count of the salesperson who manages the account for Acme Corporation, using the FROM clause syntax:

UPDATE employees SET sales_count = sales_count + 1 FROM accounts
  WHERE accounts.name = 'Acme Corporation'
  AND employees.id = accounts.sales_person;

Salesperson said "new year new me" and the database said "say less" 🔥

Scenario six: same operation, but with a sub-select in the WHERE clause instead:

UPDATE employees SET sales_count = sales_count + 1 WHERE id =
  (SELECT sales_person FROM accounts WHERE name = 'Acme Corporation');

Two roads, same destination, both slay 🫶

Scenario seven: update the contact names in an accounts table so they match whoever is currently the assigned salesperson:

UPDATE accounts SET (contact_first_name, contact_last_name) =
    (SELECT first_name, last_name FROM employees
     WHERE employees.id = accounts.sales_person);

Keeping the contact list from being all stale and awkward 😭

Scenario eight: a similar result could be accomplished with a join:

UPDATE accounts SET contact_first_name = first_name,
                    contact_last_name = last_name
  FROM employees WHERE employees.id = accounts.sales_person;

Cute, but hear me out — read the next bit 👀

Careful, bestie. The second query (the join one) may give unexpected results if employees.id is not a unique key. The first query (the sub-select one) is guaranteed to raise an error if there are multiple id matches. Also: if there's no match for a particular accounts.sales_person entry, the first query will set the corresponding name fields to NULL, whereas the second query will not update that row at all. Two different behaviours — pick accordingly, fr fr 💀

Scenario nine: refresh the statistics in a summary table so they match the current data:

UPDATE summary s SET (sum_x, sum_y, avg_x, avg_y) =
    (SELECT sum(x), sum(y), avg(x), avg(y) FROM data d
     WHERE d.group_id = s.group_id);

Summary table said "keep me updated" and we delivered 📊

Scenario ten: this one's the drama. Attempt to insert a new stock item along with the quantity of stock — but if the item already exists, update the stock count of the existing item instead. To do this without failing the entire transaction, you use savepoints:

BEGIN;
-- other operations
SAVEPOINT sp1;
INSERT INTO wines VALUES('Chateau Lafite 2003', '24');
-- Assume the above fails because of a unique key violation,
-- so now we issue these commands:
ROLLBACK TO sp1;
UPDATE wines SET stock = stock + 24 WHERE winename = 'Chateau Lafite 2003';
-- continue with other operations, and eventually
COMMIT;

The savepoint is the safety net, the rollback is the recovery, the commit is the happy ending. Character development 🧚

Scenario eleven: change the kind column of the table films in whichever row the cursor c_films is currently sitting on:

UPDATE films SET kind = 'Dramatic' WHERE CURRENT OF c_films;

Cursor-based updates, very main character energy ⭐

💜 COMPATIBILITY 💜

Okay so the compatibility tea ☕

This command conforms to the SQL standard, except that the FROM and RETURNING clauses are PostgreSQL extensions — and so is the ability to use WITH with UPDATE. So like, standard-adjacent, but with extra sparkle ✨

Some other database systems offer a FROM option in which the target table is supposed to be listed again within FROM. That is not how PostgreSQL interprets FROM. Be careful when porting applications that use this extension, bestie — this is a real gotcha, not a drill 🙈

According to the standard, the source value for a parenthesized sub-list of target column names can be any row-valued expression yielding the correct number of columns. PostgreSQL only allows the source value to be a row constructor or a sub-SELECT. And an individual column's updated value can be specified as DEFAULT in the row-constructor case, but not inside a sub-SELECT. That's just how it is, no cap 💀

And that's the whole page done, bestie! You officially know UPDATE inside and out 🌈

This lil masterpiece is from PostgreSQL 16.15, dated 2026, and lives in section 7 as UPDATE(7) — go forth and update responsibly 💖✨🎀

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