Efficiency of using Views over Joins

Question

Hi All,
Which is the most efficient way for selecting data for the following scenario :
Selecting data from three tables using JOINs alongwith FOR ALL ENTRIES or using the View for the same(as the View is available).
Performance wise, which is better?
Thanks,
Arshad

Answer 1

Arshad,
Inner Join VS Outer Join:
TABEL1 inner join TABLE2:
only entries found in TABLE1 and TABLE2 are the result.
TABEL1 outher join TABLE2:
all entries found in TABLE1 and, if found the corresponding data from TABLE2 are the result.
For inner and outer join see the below thread:
difference..inner join and outer join
Views : Data about an application object is often distributed on several tables. By defining a view, you can define an application-dependent view that combines this data. The structure of such a view is defined by specifying the tables and fields used in the view. Fields that are not required can be hidden, thereby minimizing interfaces. A view can be used in ABAP programs for data selection.
For View see the below thread:
Regarding Creating views
http://help.sap.com/saphelp_nw2004s/helpdata/en/cf/21ec77446011d189700000e8322d00/frameset.htm
ex for inner join:
Table 1 Table 2
A
B
C
D
D
E
F
G
H
a1
b1
c1
1
1
e1
f1
g1
h1
a2
b2
c2
1
3
e2
f2
g2
h2
a3
b3
c3
2
4
e3
f3
g3
h3
| a4 | b4 | c4 | 3 | |--||||--|
Inner Join
A
B
C
D
D
E
F
G
H
a1
b1
c1
1
1
e1
f1
g1
h1
a2
b2
c2
1
1
e1
f1
g1
h1
| a4 | b4 | c4 | 3 | 3 | e2 | f2 | g2 | h2 |
here common field is 'D' in both tables. after the inner join only the records from both the tables come where the D values in both the tables are same.
ex for outer join:
Table 1 Table 2
A
B
C
D
D
E
F
G
H
a1
b1
c1
1
1
e1
f1
g1
h1
a2
b2
c2
1
3
e2
f2
g2
h2
a3
b3
c3
2
4
e3
f3
g3
h3
| a4 | b4 | c4 | 3 | |--||||--|
Left Outer Join
A
B
C
D
D
E
F
G
H
a1
b1
c1
1
1
e1
f1
g1
h1
a2
b2
c2
1
1
e1
f1
g1
h1
a3
b3
c3
2
NULL
NULL
NULL
NULL
NULL
| a4 | b4 | c4 | 3 | 3 | e2 | f2 | g2 | h2 |
here all the records of table 1 come and if D value does not match in table 2 it is filled with NULL value.
View is a combination of 2 or more tables, only in the run time it contains data.
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