Question

I’ve looked all over, but can’t figure out how to update a column in a table based on subquery data when matching on a customer ID. Here’s some syntax to give an idea of what I’m trying to do:

UPDATE TableName
   SET TableName.Revenue = Z.Revenue
FROM
(
   SELECT
      CustomerID,
      sum(Revenue) as Revenue
   FROM
   (
      SELECT
         CustomerID,
         Revenue
      FROM
         TableA
      WHERE
         CustomerID in TableF
      UNION ALL
         SELECT
            CustomerID,
            Revenue
         FROM
            TableB
         WHERE
            CustomerID in TableF
   )
   GROUP BY
      CustomerID
) Z
WHERE
   TableName.CustomerID = Z.CustomerID

In essence, I’m looking to update a table column if another ID column under the same table matches an ID from a subquery. My goal is to avoid creating a whole new table from the subquery. Any help would be appreciated. Thanks.

Answer 1

Oracle does not support a FROM clause for an UPDATE. This will work:

UPDATE TableName
   SET TableName.Revenue =
(
   SELECT
      sum(Revenue) as Revenue
   FROM
   (
      SELECT
         CustomerID,
         Revenue
      FROM
         TableA
      WHERE
         CustomerID in (select CustomerID from TableF)
      UNION ALL
         SELECT
            CustomerID,
            Revenue
         FROM
            TableB
         WHERE
            CustomerID in (select CustomerID from TableF)
   )
   WHERE
      CustomerID = TableName.CustomerID
   GROUP BY
      CustomerID
);

Another option is to use the dml_expression_table syntax, which basically looks something like update (select a.x, b.y from a join b on a.a = b.b) set x = y. But that’s kinda weird and requires unique constraints to work.

Or you could use MERGE with only an UPDATE section. It’s unusual to use a MERGE for only an UPDATE, but since Oracle supports the ANSI standard it may help you use familiar syntax.