Question

I’m trying to write quite strange query and i’m having problem with if statement, so i have 2 fields deleted_1 and deleted_2 in my table which i wanna update, so this how i think it should be:

Update `messages`
  if(`deleted_1` == null) SET `deleted_1` = 1
  else
  if(`deleted_2` == null) SET `deleted_2 = 1
  ---and here goes some simple WHERE statements

but this doesn’t work so basicly i wanna check if a field is empty then update it if not check b field and if it’s empty update b field now i’m not sure maybe it’s possible to do it in more simple way, i’m quite lost here 🙂

Answer 1

UPDATE MyTable
SET deleted_2 = CASE WHEN ISNULL(deleted_1, '') == '' OR ISNULL(deleted_2, '') != '' THEN deleted_2 ELSE 1 END,
    deleted_1 = CASE WHEN ISNULL(deleted_1, '') != '' THEN deleted_1 ELSE 1 END

this is saying:

deleted_1: will be update if (deleted_1 == null)
deleted_2: will be updated if (deleted_1 != null && deleted_2 == null), 
           This is to match your if else condition