merge multiple rows having some identity to a new one that have the sum of a culumn thats is distinct between thems : i have table like this :
 id    name    qt
 0      mm     4
 1      mm     5
 2      xx     8

i want update it or get new table that will have

 id   name     qt
 0     mm      9 (sum of the two or multiple some identical )
 1     xx      8