Question

In my customer table, ref is the auto increment and ID is the customer identification number. Hence there are multiple ID for each customer (which form a history of each customer). I want to update the most recent record for each customer by setting the likelihood field to 1 in all cases – but without creating a new record.

I thought a query like this would do the job:

UPDATE customer SET likelihood = 1 WHERE customer.ref IN
(SELECT MAX(ref) FROM customer GROUP BY ID)

but I get the following error:

“#1093 – You can’t specify target table ‘customer’ for update in FROM clause”

Where am I going wrong?

Edit:
Some sample data (not the complete table)

ref | ID | likelihood | name
----+----+------------+-----
  1 |  1 |          0 | a
  2 |  2 |          0 | b
  3 |  1 |          0 | a
  4 |  2 |          0 | b
  5 |  1 |          0 | a
  6 |  1 |          0 | a

So I want to pick out:

  4 |  2 |          0 | b
  6 |  1 |          0 | a

and change them to:

  4 |  2 |          1 | b
  6 |  1 |          1 | a

Answer 1

I cannot remember whether it will allow a self join in an update. Give this a try –

UPDATE customer c1
LEFT JOIN customer c2
    ON c1.ID = c2.ID
    AND c1.ref < c2.ref
SET c1.likelihood = 1
WHERE c2.ID IS NULL

EDIT I have changed the column used in the second join condition from ID to ref.