A) CREATE TABLE toplevelcust (number INTEGER PRIMARY KEY, <span> name TEXT, address TEXT, balance DOUBLE, credit DOUBLE</span>);
b) select number, name, credit - balance from toplevelcust
c) This I cannot answer
Answer:
The database can detect only system-defined events.
Explanation:
A trigger is like a stored procedure that Oracle Database invokes automatically whenever a specified event occurs.trigger is like a stored procedure that Oracle Database invokes automatically whenever a specified event occurs.
Both triggers and constraints can constrain data input, but they differ significantly.
A constraint applies to both existing and new data. For example, if a database column has a NOT NULL constraint, then its existing data is NOT NULL and no DML statement can violate the NOT NULL constraint.
A trigger applies only to new data. For example, a trigger can prevent a DML statement from inserting a NULL value into a database column, but the column might contain NULL values that were inserted into the column before the trigger was defined or while the trigger was disabled
Answer:
He meant that you a USB drive in case your computer broke
