Is your feature request related to a problem? Please describe.
Example of schema:

"sales":{
   "sql":"sum(${CUBE}."Sales")"
},
"wholesaleCost":{
   "sql":"sum(${CUBE}."WholesaleCost")"
},
"profit":{
   "sql":"${sales} - ${wholesaleCost}"
},
"someCoef":{
   "sql":"${profit} / ${sales}"
}

This schema is not working. someCoef generates wrong formula${sales} - ${wholesaleCost}/${sales} while correct is (${sales} - ${wholesaleCost})/${sales}
It can be fixed in 2 ways:

1. someCoef sql should be (${profit}) / ${sales} (profit inside brackets)
2. profit sql should be (${sales} - ${wholesaleCost}) (whole formula inside brackets)

Describe the solution you'd like
Cube should check and automatically add brackets if needed