Writing an SQL query for a custom field extended to subiekt gt

I need to write a SQL query for an extended custom field (e.g., Selected Contractor extended custom field, or Selected Contractor regular field completion) that will return the number of pieces of goods on orders from customers (ZK) not fulfilled with reservation. (all warehouses) Ideally, the query should return one of 5 results: few, average, optimal, many, very many: < 2999 total units in ZK - little 3000 - 3999 - average 4000 - 4999 - optimally 5000 - 9999 - a lot > 10000 - very much We want to update this value with a trigger, for example, at midnight. Then by external integration we want to send the value of this custom field from the database table. Please send us a quote and possible implementation time.