The error message
Msg 1750, Level 16, State 0, Line 1
Could not create constraint. See previous errors.
is a run time error message of severity level 16. It can be generated at all versions of SQL Server. This error message appears when as a result of a previous error a constraint cannot be created. As errors of Severity Level 16 are generated and can be corrected by the user. The root cause for the previous error must be corrected so that the constraint can be created successfully.