Set Theoretic Operation

Name	Symbol	Keyboard Form	Example
UNION	∪	UNION	R∪S, or R UNION S
INTERSECTION	∩	INTERSECT	R∩S, or R INTERSECT S
DIFFERENCE	—	— or MINUS	R—S, or R MINUS S
PRODUCT	×	TIMES	R×S, or R TIMES S

Tables R and S are compatible if they have the same headings; that is, if Head(R)=Head(S), with attributes chosen from the same domains and with the meanings.

R A B C a1 b1 c1 a1 b2 c3 a2 b1 c2 S A B C a1 b1 c1 a1 b1 c2 a1 b2 c3 a3 b2 c3

Let R and S be two compatible tables, where Head(R)=Head(S)=A1…An. Union The union of R and S is the table R∪S, with the same heading, consisting of all rows that are in R or in S or in both. Intersection The intersection of R and S is the table R∩S, with the same heading, consisting of all rows that are in both R and S.

R∪S A B C a1 b1 c1 a1 b2 c3 a2 b1 c2 a1 b1 c1 a1 b1 c2 a1 b2 c3 a3 b2 c3 R∩S A B C a1 b1 c1 a1 b2 c3

Difference The difference of R and S is the table R–S, with the same heading, consisting of all rows that are in R but do not appear in S.

S–R A B C a1 b1 c2 a3 b2 c3 R–S A B C a2 b1 c2