InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
What Is Difference Between Unique And Primary Key Constraints? |
|
Answer» A table can have only one PRIMARY KEY whereas there can be any number of UNIQUE keys. The COLUMNS that COMPOSE PK are automatically define NOT NULL, whereas a column that compose a UNIQUE is not automatically defined to be mandatory MUST ALSO specify the column is NOT NULL. A table can have only one PRIMARY KEY whereas there can be any number of UNIQUE keys. The columns that compose PK are automatically define NOT NULL, whereas a column that compose a UNIQUE is not automatically defined to be mandatory must also specify the column is NOT NULL. |
|