# Update (SQL)

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{{short description|SQL statement}}
{{redirect|UPDATE|other uses|Update (disambiguation)}}
An [SQL](/source/SQL) '''UPDATE''' statement changes the data of one or more records in a [table](/source/Table_(database)).  Either all the rows can be updated, or a subset may be chosen using a <code>WHERE</code> [condition](/source/Condition_(SQL)). If a condition is not used, then every row of the value is updated.<ref name="phpandmysqlbook">{{cite book |author1=Jon Duckett |author2=Emme Stone |author3=Chris Ullman |url=https://phpandmysql.com/buy/ |title=PHP & MySQL: server-side web development |publisher=John Wiley & Sons, Inc. |publication-place=[Hoboken, New Jersey](/source/Hoboken%2C_New_Jersey) |lang=en-US |isbn=978-1-119-14921-7 |lccn=2021951353 |year=2022 |access-date=28 April 2026 |archive-url=https://web.archive.org/web/20250430043459/https://phpandmysql.com/buy/ |archive-date=30 April 2025 |url-status=live}}</ref>{{rp|p=426}}

The <code>UPDATE</code> statement has the following form:<ref name="mysql-doc">{{cite web |url=https://dev.mysql.com/doc/refman/8.4/en/update.html |title=15.2.17 UPDATE Statement |publisher=Oracle |access-date=March 28, 2026}}</ref><ref name="phpandmysqlbook"/>{{rp|p=426}}

:<code>'''UPDATE''' ''table_name'' SET ''column_name'' = ''value'' [, ''column_name'' = ''value ...''] [WHERE ''condition'']</code>

For the <code>UPDATE</code> to be successful, the user must have data manipulation privileges (<code>UPDATE</code> privilege) on the table or [column](/source/Column_(database)) and the updated value must not conflict with all the applicable constraints (such as [primary key](/source/primary_key)s, unique indexes, [<code>CHECK</code> constraints](/source/Check_Constraint), and [<code>NOT NULL</code>](/source/Null_(SQL)) constraints).

In some databases, such as [PostgreSQL](/source/PostgreSQL), when a [FROM clause](/source/From_(SQL)) is present, the target table is joined to the tables mentioned in the fromlist, and each output row of the join represents an update operation for the target table. When using FROM, one 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.<ref>{{Cite web|url=http://www.postgresql.org/docs/8.1/static/sql-update.html|title=UPDATE|date=January 2012|publisher=PostgreSQL}}</ref>

Because of this indeterminacy, referencing other tables only within sub-selects is safer, though often harder to read and slower than using a join.{{cn|date=March 2026}}

MySQL does not conform to the ANSI standard.{{cn|date=March 2026|reason=Removed unreliable StackOverflow citation}}

==Examples==
Set the value of column ''C1'' in table ''T''  to 1, only in those rows where the value of column ''C2'' is "a".

<syntaxhighlight lang="sql">
UPDATE T
   SET C1 = 1
 WHERE C2 = 'a'
</syntaxhighlight>

In table ''T'', set the value of column ''C1'' to 9 and the value of ''C3'' to 4 for all rows for which the value of column ''C2'' is "a".

<syntaxhighlight lang="sql">
UPDATE T
   SET C1 = 9,
       C3 = 4
 WHERE C2 = 'a'</syntaxhighlight>

Increase value of column ''C1'' by 1 if the value in column ''C2'' is "a".

<syntaxhighlight lang="sql">
UPDATE T
   SET C1 = C1 + 1
 WHERE C2 = 'a'</syntaxhighlight>

Prepend the value in column ''C1'' with the string "text" if the value in column ''C2'' is "a".

<syntaxhighlight lang="sql">
UPDATE T
   SET C1 = 'text' || C1
 WHERE C2 = 'a'</syntaxhighlight>

Set the value of column ''C1'' in table ''T1'' to 2, only if the value of column ''C2'' is found in the sublist of values in column ''C3'' in table ''T2'' having the column ''C4'' equal to 0.
<syntaxhighlight lang="sql">
UPDATE T1
   SET C1 = 2
 WHERE C2 IN ( SELECT C3
                 FROM T2
                WHERE C4 = 0)
</syntaxhighlight>
One may also update multiple columns in a single update statement:

<syntaxhighlight lang="sql">
UPDATE T
   SET C1 = 1,
       C2 = 2</syntaxhighlight>

Complex conditions and JOINs are also possible:

<syntaxhighlight lang="sql">
UPDATE T
   SET A = 1
 WHERE C1 = 1
   AND C2 = 2</syntaxhighlight>

Some databases allow the non-standard use of the FROM clause:
<syntaxhighlight lang="sql">
UPDATE a
   SET a.[updated_column] = updatevalue
  FROM articles a
       JOIN classification c
         ON a.articleID = c.articleID
 WHERE c.classID = 1
</syntaxhighlight>

Or on Oracle systems (assuming there is an index on classification.articleID):
<syntaxhighlight lang="sql">
UPDATE
(
  SELECT *
    FROM articles
    JOIN classification
      ON articles.articleID = classification.articleID
   WHERE classification.classID = 1
)
SET [updated_column] = updatevalue
</syntaxhighlight>
With long name of table:
<syntaxhighlight lang="sql">
UPDATE MyMainTable AS a
SET a.LName = Smith
WHERE a.PeopleID = 1235
</syntaxhighlight>

==Potential issues==
* See [Halloween Problem](/source/Halloween_Problem).  It is possible for certain kinds of <code>UPDATE</code> statements to become an [infinite loop](/source/infinite_loop) when the <code>WHERE</code> clause and one or more <code>SET</code> clauses may utilize an intertwined [index](/source/Index_(database)).

==References==
{{Reflist}}
{{SQL}}

{{DEFAULTSORT:Update (Sql)}}
Category:SQL keywords
Category:Articles with example SQL code

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Adapted from the Wikipedia article [Update (SQL)](https://en.wikipedia.org/wiki/Update_(SQL)) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Update_(SQL)?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.