MYSQL LEFT JOIN add condition on other table

Question

select principalTable.X, secondTable.ART, secondTable.DETT
from 
(principalTable

left join thirdTable
on on principalTable.X = thirdTable.X

left join secondTable
on principalTable.ART = secondTable.ART and thirdTable.ID = secondTable.ID
)

I've got 3 tables that show some cross data from this query, I need a condition to select only the data from the secondtable that had a common index with the thirdtable , else without the and condition there can be many incorrect results. I've tried the same query with the and applied to principalTable and with that,this work. With the condition applied on the thirdTable it won't work.

Every advice is really appreciated.

Answer 1

try the following query.

select principalTable.X, secondTable.ART, secondTable.DETT 
form principalTable pt,secondTable st,thirdTable tt
where pt.X = tt.X AND pt.ART = st.ART AND st.ID = tt.ID