Question

I’d like do something like this:

1. In table TAGS find a row with name=’someName’, and remeber it’s id
2. In the same table find another row with someCondition and set in this row col refference=the id from above

Tried to do this using a subquery, but mysql refused saying I can’t subquery a table that I’m updating in the main query.

How can I otherwise implement the above idea?

Thank you

Answer 1

you can do this

    update TAGS set 
    reference = 
        (select my_id from 
            (select id as my_id from TAGS where name='someName') 
         as SUB_TAGS) 
    where someCondition;

Not advisable though.

---

Edit#1 You can avoid the sub-queries altogether — as taspeotis rightly mentioned, by joining the same table with the criteria. Here goes the code for that:

  UPDATE 
    TAGS t1, TAGS t2 
  SET 
    t1.reference = t2.id
  WHERE
        t2.name = 'someName' 
    AND
        t1.someField = someCondition;

This is a better approach.