# UPDATE **Applies to:** ❌ Data 360 SQL ✅ Tableau Hyper API Update rows in a table. ## Syntax ```sql [ WITH [RECURSIVE] [, ...] ] UPDATE [ [ AS ] alias ] SET { = { | DEFAULT } | ( [, ...] ) = [ ROW ] ( { | DEFAULT } [, ...] ) | ( [, ...] ) = ( ) } [, ...] [ FROM ] [ WHERE ] [ RETURNING { * | } [ [ AS ] ] [, ...] ] ``` ## Description `UPDATE` changes the values of the specified columns in all rows that satisfy the condition. Only the columns to be modified need be mentioned in the `SET` clause; columns not explicitly modified retain their previous values. 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. The `ROW` keyword is optional and does not add any semantics in this case. It is required according to the SQL standard, and for compatibility with the standard, we recommend using the `ROW` keyword. 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`. ## Parameters - `` - : The `WITH` clause allows you to specify one or more subqueries that can be referenced by name in the `UPDATE` query. See [SELECT](/docs/data/data-cloud-query-guide/references/dc-sql-reference/select.md) for details. - `` - : The name (optionally schema-qualified) of the table to update. - `` - : 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`. - `` - : The name of a column in the table named by ``. 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. - `` - : 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). - `` - : 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. - `` - : A list of table expressions, allowing columns from other tables to appear in the `WHERE` condition and the update expressions. This is similar to the list of tables that can be specified in the [FROM](/docs/data/data-cloud-query-guide/references/dc-sql-reference/select.md) clause of a `SELECT` statement. Note that the target table must not appear in the ``, unless you intend a self-join (in which case it must appear with an alias in the ``). - `` - : An expression that returns a value of type `boolean`. Only rows for which this expression returns `true` will be updated. - `` - : 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 `` or table(s) listed in `FROM`. Write `*` to return all columns. - `` - : A name to use for a returned column. ## Outputs 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. ## Referring to other tables When a `FROM` clause is present, what essentially happens is that the target table is joined to the tables mentioned in the ``, 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. ## Examples Change the word `Drama` to `Dramatic` in the column kind of the table films: ```sql UPDATE films SET kind = 'Dramatic' WHERE kind = 'Drama'; ``` Adjust temperature entries and reset precipitation to its default value in one row of the table weather: ```sql UPDATE weather SET temp_lo = temp_lo+1, temp_hi = temp_lo+15, prcp = DEFAULT WHERE city = 'San Francisco' AND date = '2003-07-03'; ``` Perform the same operation and return the updated entries: ```sql 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; ``` Use the alternative column-list syntax to do the same update: ```sql UPDATE weather SET (temp_lo, temp_hi, prcp) = (temp_lo+1, temp_lo+15, DEFAULT) WHERE city = 'San Francisco' AND date = '2003-07-03'; ``` Increment the sales count of the salesperson who manages the account for Acme Corporation, using the `FROM` clause syntax: ```sql UPDATE employees SET sales_count = sales_count + 1 FROM accounts WHERE accounts.name = 'Acme Corporation' AND employees.id = accounts.sales_person; ``` Perform the same operation, using a sub-select in the `WHERE` clause: ```sql UPDATE employees SET sales_count = sales_count + 1 WHERE id = (SELECT sales_person FROM accounts WHERE name = 'Acme Corporation'); ``` Update contact names in an accounts table to match the currently assigned salesperson: ```sql UPDATE accounts SET (contact_first_name, contact_last_name) = (SELECT first_name, last_name FROM employees WHERE employees.id = accounts.sales_person); ``` A similar result could be accomplished with a join: ```sql UPDATE account SET contact_first_name = first_name, contact_last_name = last_name FROM employees WHERE employees.id = accounts.sales_person; ``` However, the second query may give unexpected results if employees.id is not a unique key, whereas the first query is guaranteed to raise an error if there are multiple id matches. Also, if there is 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. Update statistics in a summary table to match the current data: ```sql 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); ``` ## Compatibility This command conforms to the SQL standard, except that the `FROM` and `RETURNING` clauses are Hyper extensions (also available in PostgreSQL), as is the ability to use `WITH` with `UPDATE`. 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 Hyper interprets `FROM`. Be careful when porting applications that use this extension.