I don't know the first thing about SQL. So don't assume I already know anything when you're writing answer. I know I'm asking way too much for free, but time is running out.CREATE TABLE R1 (a INT PRIMARY KEY,b INT);CREATE TABLE R2 (c INT PRIMARY KEY,d INT PREFERENCES R1(a));CREATE TABLE R3 (e INT PRIMARY KEY,f INT CHECK(f IN(SELECT a FROM R1)));
Assume that the table R1 contains 3 rows: (1,10),(2,10), and (3,20), while R2 and R3 are empty. Which of the following sequences of statements would not be allowed by SQL?(a)INSERT INTO R3 VALUES(5,2);DELETE FROM R1 WHERE a=2;INSERT INTO R2 VALUES(1,1);
(b)INSERT INTO R2 VALUES(1,1);DELETE FROM R1 WHERE a=2;INSERT INTO R3 VALUES(6,1);
(c)INSERT INTO R3 VALUES(6,1);UPDATE R1 SET a=4 WHERE a=3;INSERT INTO R2 VALUES(10,2);
(d)DELETE FROM R1 WHERE a=2;INSERT INTO R2 VALUES(1,1);INSERT INTO R3 VALUES(5,2);