Re: Time performance in query Inner Join

[Rick James]

In addition to Peter's toned down request, ...

Let's see the EXPLAIN for that SELECT.

SHOW TABLE STATUS LIKE '_tbl1';
SHOW TABLE STATUS LIKE '_tbl2';
might also help.

WHERE ... C.MCR_Cod ='DNO'
begs for
INDEX(MCR_Cod)

GROUP BY MCR_Cod, MCR_Clt, MCR_Den
Would probably benefit
INDEX(MCR_Cod, MCR_Clt, MCR_Den)

Don't add both indexes, only the longer one.

ALTER TABLE _tbl2
ADD INDEX(MCR_Cod, MCR_Clt, MCR_Den);