MySQL notes

Notes for working with MySQL

Basic table join for update from one table to another with where clause

UPDATE tableA a
  JOIN tableB b
    ON a.a_id = b.a_id
  JOIN tableC c
    ON b.b_id = c.b_id
   SET b.val = a.val+c.val
 WHERE a.val > 10
   AND c.val > 10;

Another way

UPDATE T1, T2,
[INNER JOIN | LEFT JOIN] T1 ON T1.C1 = T2.C1
SET T1.C2 = T2.C2, 
    T2.C3 = expr
WHERE condition