mysql select from one or another table

Question

Thanks, for your help, I posted a simplified version of my problem but I really didn't understand how to apply the left join in the big one that is this:

SELECT d.type, 
       d.item , 
       if(d.type='I', a.name, b.name) as name, 
       if(d.type='I', c.price,0) as price, 
       if(d.type='I',if(d.taxes='yes', 
       (c.priceWithTax*d.weight), (c.price*d.weight)),0) as totalprice 
  FROM d 
inner join a on d.item=a.id 
inner join c on d.item=c.item
     where c.sede =1

The problem is that when d.type='I' I need the items from table a, but if d.type='S' I need the items from table B, the prices are on table c.

Thank you very much.

Answer 1

If you need something like this, that's clearly indicates that your database structure is wrong.
It should be one table, and your query become plain and easy.

Answer 2

select
  a.col1,
  b.col1,
  coalesce(c.col1,0)
from a inner join b on a.col0=b.col1
  left outer join c on b.col2='apple' and c.col1=b.col0

Things to learn:

• outer joins
• function COALESCE()
• use single-quotes for string literals in SQL, not double-quotes

---

I have an rawFood table, a cookedFood table and a Menu table and the menu table has things from both, rawFood and cookedFood, thats why I need to join that way

You need to have a single food table, and give it a column that notes the difference between raw and cooked food.

Answer 3

You can use a left join

select
    a.col1,
    b.col1,
    ifnull(c.col1,0)
from a 
    inner join b on a.col0=b.col1
    left join c on (c.col1 = b.col0 and b.col2="apple")
where
    b.col2 != "apple" or (b.col2 = "apple" and c.col1 is not null)