Some of you would be so kind to explain to me how this SQL query is working, I understand it in part but not in its entirety. I clarify that it only affects two tables. Thank you
UPDATE PRODUCTO SET Cantidad = T2.stock
FROM PRODUCTO T1
INNER JOIN (
SELECT T3.id, T3.Cantidad - T4.Cantidad Stock
FROM PRODUCTO T3
INNER JOIN compra T4 ON T3.id = T4.id
) T2 ON T1.id = T2.id WHERE t2.id = 2
what I understand is: UPDATE to table PRODUCT SET column QUANTITY = ??? from the PRODUCT table t1, I understand it is a reference to PRODUCT?? INNER JOIN who is T3? what I understand is table3.id, it refers to T3 - T4 ????
FROM product and now refers to it as T3?? INNER JOIN column BUY t4?? can you refer columns too??
So better explain it to me. :)