BACS 485
Translating
E/R to Relational Notation
BACS485 – E/R to Relational Notation
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Relational Notation
Relational Notation is a shorthand way to
represent E/R diagrams. It is a half-way step
between an abstract tool (i.e., E/R diagrams)
and an implementation specific tool (i.e., SQL
Create Table commands). The format is as
follows:
Table-name(key-attribute, attribute-1,… attribute-N)
BACS485 – E/R to Relational Notation
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Relational Notation
The basic rules of translating E/R diagrams to Relational Notation are
given below:
 Each entity becomes a table
 Each attribute on the table becomes an attribute on the table
 Primary keys are underlined
 Foreign keys are underlined with a dashed line
 In 1:1, the foreign key can be on either side of the relation (context
dependent)
 In 1:N, the foreign key goes on the ‘N’ side
 In M:N, the relation becomes a table and the key for the new table is
the concatenated primary keys of the original tables
 In sub-type/super-type, the primary key of the sub-type(s) is the same
as the super-type (thus, no “foreign key”)
BACS485 – E/R to Relational Notation
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1:1
E/R to Relational Notation
A
B
Table1

D
C
Rel
Translates to 2 tables:
Table1 (A,B,C,D)
OR
Table2 (D,E,F)
E
F
Table2
Table1 (A,B,C)
Table2 (D,E,F,A)
pick one depending upon context, red letter is foreign key
BACS485 – E/R to Relational Notation
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1:1
Relational Notation to E/R
Translate from 2 tables:
Table1 (X,Y,Z)
OR
Table2 (L,M,N,X)

Table1 (X,Y,Z,L)
Table2 (L,M,N)
pick one depending upon context, red letter is foreign key
X
Y
L
Z
Table1
BACS485 – E/R to Relational Notation
Rel
M
N
Table2
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1:N
E/R to Relational Notation
A
B
Table1

D
C
Rel
E
F
Table2
Translates to 2 tables:
Table1 (A,B,C)
Table2 (D,E,F,A)
red letter is foreign key
BACS485 – E/R to Relational Notation
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1:N
Relational Notation to E/R
Translate from 2 tables:
Table1 (X,Y,Z,L)
Table2 (L,M,N)

red letter is foreign key
X
Y
L
Z
Table1
BACS485 – E/R to Relational Notation
Rel
M
N
Table2
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Simple M:N
E/R to Relational Notation
A
B
Table1

D
C
Rel
E
F
Table2
Translates to 3 tables:
Table1 (A,B,C)
Table2 (D,E,F)
Table3 (A,D)
Notice that there is no foreign key
BACS485 – E/R to Relational Notation
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Simple M:N
Relational Notation to E/R
Translate from 3 tables:
Table1 (X,Y,Z)
Table2 (L,M,N)
Table3 (X,L)

X
Y
L
Z
Table1
BACS485 – E/R to Relational Notation
Rel
M
N
Table2
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More Complex M:N
E/R to Relational Notation
A
B
D
C
E
F
X
Table1

Rel
Table2
Translates to 3 tables:
Table1 (A,B,C)
Table2 (D,E,F)
Table3 (A,D,X)
Notice that relationship attribute is attached to new table
BACS485 – E/R to Relational Notation
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More Complex M:N
Relational Notation to E/R
Translate from 3 tables:
Table1 (X,Y,Z)
Table2 (L,M,N)
Table3 (X,L,P)

X
Y
L
Z
M
N
P
Table1
BACS485 – E/R to Relational Notation
Rel
Table2
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More Complex M:N
E/R to Relational Notation
A
B
D
C
E
F
X
Table1

Rel
Table2
Translates to 3 tables:
Table1 (A,B,C)
Table2 (D,E,F)
Table3 (A,D,X)
Notice that relationship attribute is attached to new table
BACS485 – E/R to Relational Notation
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More Complex M:N
E/R to Relational Notation

H
I
J
Table3
A
B
Table1
C
D
Rel
E
F
Translates to 4 tables:
Table1 (A,B,C)
Table2 (D,E,F)
Table3 (H,I,J)
Table4 (A,D,H,K)
Table2
K
BACS485 – E/R to Relational Notation
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Sub-Type / Super-Type
E/R to Relational Notation
A
B
C

Table1 (A,B,C)
Table2 (A,D,E,F)
Table3 (A,H,I,J)
Table1
E
Notice that Table2 and Table3
do not have a key in the E/R.
Table3
Table2
D
F
BACS485 – E/R to Relational Notation
Translates to 3 tables:
H
I
J
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