CREATE TABLE Assets (maintenance_contract_id VARCHAR)
CREATE TABLE Maintenance_Contracts (maintenance_contract_id VARCHAR)

How many assets does each maintenance contract contain? List the number and the contract id.
SELECT COUNT(*), T1.maintenance_contract_id FROM Maintenance_Contracts AS T1 JOIN Assets AS T2 ON T1.maintenance_contract_id = T2.maintenance_contract_id GROUP BY T1.maintenance_contract_id
SELECT COUNT(*), "T1"."maintenance_contract_id" FROM "Maintenance_Contracts" AS "T1" JOIN "Assets" AS "T2" ON "T1"."maintenance_contract_id" = "T2"."maintenance_contract_id" GROUP BY "T1"."maintenance_contract_id"