SQL With... Update

Question

Is there any way to do some kind of "WITH...UPDATE" action on SQL?

For example:

WITH changes AS
  (...)
UPDATE table
SET id = changes.target
FROM table INNER JOIN changes ON table.id = changes.base
WHERE table.id = changes.base;

Some context information: What I'm trying to do is to generate a base/target list from a table and then use it to change values in another table (changing values equal to base into target)

Thanks!

Answer 1

You can use merge, with the equivalent of your with clause as the using clause, but because you're updating the field you're joining on you need to do a bit more work; this:

merge into t42
using (
  select 1 as base, 10 as target
  from dual
) changes
on (t42.id = changes.base)
when matched then
update set t42.id = changes.target;

.. gives error:

ORA-38104: Columns referenced in the ON Clause cannot be updated: "T42"."ID"

Of course, it depends a bit what you're doing in the CTE, but as long as you can join to your table withint that to get the rowid you can use that for the on clause instead:

merge into t42
using (
  select t42.id as base, t42.id * 10 as target, t42.rowid as r_id
  from t42
  where id in (1, 2)
) changes
on (t42.rowid = changes.r_id)
when matched then
update set t42.id = changes.target;

If I create my t42 table with an id column and have rows with values 1, 2 and 3, this will update the first two to 10 and 20, and leave the third one alone.

SQL Fiddle demo.

It doesn't have to be rowid, it can be a real column if it uniquely identifies the row; normally that would be an id, which would normally never change (as a primary key), you just can't use it and update it at the same time.