Acumuladores, MySQL

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#MySQL 5.7.12
#please drop objects you've created at the end of the script 
#or check for their existance before creating
#'\\' is a delimiter
# drop table Errores \\

create table Errores (
    Titulo varchar(100), 
    Cantidad INT
) \\

insert into Errores (Titulo, Cantidad)
VALUES  ('Error A', 15), 
        ('Error B', 85), 
        ('Error C', 25), 
        ('Error D', 64), 
        ('Error E', 10) \\

SELECT *,
    C.ACUMULADO/Total
    FROM (SELECT   t.Titulo,
                   t.Cantidad,
                   @acum := @acum + t.Cantidad AS ACUMULADO,
                   tot.Total   
                   FROM Errores t
                   JOIN (SELECT @acum := 0) r
                   JOIN (SELECT SUM(Cantidad) as 'Total' FROM Errores) tot
                   ORDER BY t.Cantidad desc
          ) C
          WHERE C.ACUMULADO/Total <= 0.8
          ORDER BY Cantidad desc \\

SELECT *    
    FROM (SELECT   t.Titulo,
                   t.Cantidad,
                   (CASE WHEN @acum/tot.Total < 0.8 THEN 0 ELSE 1 END) as 'Mayor80',
                   (@acum := @acum + t.Cantidad)/tot.Total as 'Porcentaje'
                   FROM Errores t
                   JOIN (SELECT @acum := 0) r
                   JOIN (SELECT SUM(Cantidad) as 'Total' FROM Errores) tot
                   ORDER BY t.Cantidad desc
          ) C
          WHERE Mayor80 = 0
          ORDER BY Cantidad desc
          \\

drop table Errores \\


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