2. One important constraint in a relational database environment is that a primary key uniquely identifies each row in a data table. This principle is called the a. referential integrity rule. b. entity integrity rule. c. unique primary key rule. d. foreign key rule. .3. Given the following events, choose the correct ord that occurs first. isud shared a resource was Conselero.com Crow's feet-> EVENT X (1.-) crow's feet-> EVENTO f. Q. Y. X (0,-) 0 EVENT Q EVENT Y