Add a table-level PRIMARY KEY constraint to the EMPLOYEE table using the ID column.  The constraint should be named at creation. (Which means you'll need to drop the table, then recreate.) Create a PRIMARY KEY constraint on the DEPARTMENT table using the ID column.  The constraint should be named at creation. (Which means you'll need to drop the table, then recreate.) Add a foreign key reference on the EMPLOYEE table that will ensure that the employee is not assigned to a nonexistent department. Confirm that the constraints were added by querying USER_CONSTRAINTS.  Note the types and names of the constraints and include them in your statement comments. Display the object names and types from the USER_OBJECTS data dictionary view for EMPLOYEE and DEPARTMENT tables.  You will want to format the columns for readability.  Provide comments that include the new tables and indexes created. Modify the EMPLOYEE table by adding a SALARY column of NUMBER data type, precision 7.  Confirm your modifications by checking the description of the table.

SQL: 

1. Add a table-level PRIMARY KEY constraint to the EMPLOYEE table using the ID column.  The constraint should be named at creation. (Which means you'll need to drop the table, then recreate.)
2. Create a PRIMARY KEY constraint on the DEPARTMENT table using the ID column.  The constraint should be named at creation. (Which means you'll need to drop the table, then recreate.)
3. Add a foreign key reference on the EMPLOYEE table that will ensure that the employee is not assigned to a nonexistent department.
4. Confirm that the constraints were added by querying USER_CONSTRAINTS.  Note the types and names of the constraints and include them in your statement comments.
5. Display the object names and types from the USER_OBJECTS data dictionary view for EMPLOYEE and DEPARTMENT tables.  You will want to format the columns for readability.  Provide comments that include the new tables and indexes created.
6. Modify the EMPLOYEE table by adding a SALARY column of NUMBER data type, precision 7.  Confirm your modifications by checking the description of the table.