mysql - Arithmetic operations between SQL select results -


hi need part of bigger script:

select group_concat(distinct concat('(sum(case when columna = "'  ,columna, ' "then 1 else 0 end))/(select total     hd_totals columna = "'  ,columna, ' ") "'  ,columna, ' "'))  table inner join.....

the problem can't / operation because gives error, if select output single value. don't know how use aliases or store in variable because it's rather complex (to me) environment i'm creating here...

what : use cast have decimal type, , use coalesce prevent null values? 

select group_concat(distinct concat('coalesce(cast((sum(case when columna = "'  ,columna, ' "then 1 else 0 end)) decimal(10,4)),0)/coalesce(cast((select total     hd_totals columna = "'  ,columna, ' ") decimal(10,4)),0.01) "'  ,columna, ' "'))  table inner join.....

note : there arbitrary constant 0.01 prevent dividing 0.

more important note : if add case when check don't divide 0.


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