You administer a Microsoft SQL Server 2012 database. The database contains a table named
Employee. Part of the Employee table is shown in the exhibit. (Click the Exhibit button.)
Confidential information about the employees is stored in a separate table named EmployeeData.
One record exists within EmployeeData for each record in the Employee table. You need to assign
the appropriate constraints and table properties to ensure data integrity and visibility. On which
column in the Employee table should you a create a unique constraint?
A.
DateHired
B.
DepartmentID
C.
EmployeelD
D.
EmployeeNum
E.
FirstName
F.
JobTitle
G.
LastName
H.
MiddleName
I.
ReportsToID
d
D is correct. EmployeeNum column in the Employee table should you create a unique constraint”. You need to define uniqueness not referential integrity between both tables.
D
it’s messIt’s a bit confusing for me. EmployeeID should be correct as well. Could someone tell me why A is not correct?
Because the EmployeeID has a pk constraint which also creates a unique reference. A value can’t be entered twice when a pk constraint exists on a column.
The only column that should have unique values within the table but no constraint yet is EmployeeNum, D should be the correct answer.