Demaestro - 4:08 pm on Jul 12, 2010 (gmt 0)
Depending on your data there are a few ways to do this.
If the image field is null then you can use coalesce.
select coalesce(img_field, '/images/placeholder') as img_field from table
If the image field is an empty string then you may want to use a case/switch statement or an if.
when (img_field == '') then '/images/placeholder'
if (img_field=='','/images/placeholder', img_field)
My syntax might be a little off, I am going from memory. but if you search for "sql case" or "sql coalesce" or "sql if else" you will find lots of good examples.