# 13.13. Match Join Framework¶

The general framework for Match Join with two relations A and B include these primary aspects of the circumstances:

1. Whether input relations are:
• Different Bases

• Same Base

• Same Relation

2. What the Symmetry of the Match Join is:
• Non-Symmetric-A, when the columns being matched have a M - 1 correspondence

• Symmetric-Either, when the columns being matched have a 1 - 1 correspondence

• Symmetric-Pair, when the columns being matched have a M - M correspondence

3. What ‘works-on’ columns are being matched, in terms of A’s identifier and B’s identifier, as given in the following table:

Works-on column possibilities for Match Join

Letter

Short Name

Input relation’s columns being matched

E

Exactly

exactly its id (all identifying columns)

M

More

more than its id (id +)

S

Some

some of its id columns, but not all

O

Overlapping

some of its id columns, + some non-id columns

D

Disjoint

disjoint from id columns (no id columns)

The nine total examples we presented in detail are as follows in this table:

Circumstances For Match Joins In this Chapter

Bases of A, B

A data to B data through works-on cols

Symmetry for symbol

Input relation columns being matched

Different Base, Achievement Skill

M-1

Non-Symmetric-A

Aid(D),Bid(E)

Different Base, Achievement Skill

M-1

Non-Symmetric-A

Aid(D),Bid(M)

Different Base, Aspiration Creature

M-1

Non-Symmetric-A

Aid(S),Bid(E)

Different Base, Creature Skill

M-M

Symmetric-Pair

Aid(D),Bid(D)

Same Base, Aspiration Creature- Skill Pair

1-1

Symmetric-Either

Aid(M),Bid(M)

Same Base, TeamSkill Skill

1-1

Symmetric-Either

Aid(E),Bid(E)

Same Base, Achievement Aspiration

1-1

Symmetric-Either

Aid(E),Bid(E)

Same Relation, Creature Creature

M-1

Non-Symmetric-A

Aid(D),Bid(E)

Same Relation, Creature Creature

M-M

Symmetric-Pair

Aid(D),Bid(D)

The first three are the Different Base, M -1, but the works-on columns are different. The generic conceptual schema fragment and precedence charts for these 3 cases looks the same. There were 3 Same Base, 1 - 1 cases presented, two of which use the same generic form of precedence chart. Overall, there are 6 generic circumstances with precedence charts shown below, as a means to orient you to these common cases and be able to apply them to other situations.