Difference between inner join and outer join

Question

1.Difference between inner join and outer join
2.wht is the difference in using hide and get crusor value in interactive.
3. Using join is better or views in writting program . Which is better.

Answer 1

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 |
    |--||||||||--|
Example
Output a list of all flights from Frankfurt to New York between September 10th and 20th, 2001 that are not sold out:
DATA: DATE   LIKE SFLIGHT-FLDATE,
      CARRID LIKE SFLIGHT-CARRID,
      CONNID LIKE SFLIGHT-CONNID.
SELECT FCARRID FCONNID F~FLDATE
    INTO (CARRID, CONNID, DATE)
    FROM SFLIGHT AS F INNER JOIN SPFLI AS P
           ON FCARRID = PCARRID AND
              FCONNID = PCONNID
    WHERE P~CITYFROM = 'FRANKFURT'
      AND P~CITYTO   = 'NEW YORK'
      AND F~FLDATE BETWEEN '20010910' AND '20010920'
      AND FSEATSOCC < FSEATSMAX.
  WRITE: / DATE, CARRID, CONNID.
ENDSELECT.
If there are columns with the same name in both tables, you must distinguish between them by prefixing the field descriptor with the table name or a table alias.
Note
In order to determine the result of a SELECT command where the FROM clause contains a join, the database system first creates a temporary table containing the lines that meet the ON condition. The WHERE condition is then applied to the temporary table. It does not matter in an inner join whether the condition is in the ON or WHEREclause. The following example returns the same solution as the previous one.
Example
Output of a list of all flights from Frankfurt to New York between September 10th and 20th, 2001 that are not sold out:
DATA: DATE   LIKE SFLIGHT-FLDATE,
      CARRID LIKE SFLIGHT-CARRID,
      CONNID LIKE SFLIGHT-CONNID.
SELECT FCARRID FCONNID F~FLDATE
    INTO (CARRID, CONNID, DATE)
    FROM SFLIGHT AS F INNER JOIN SPFLI AS P
           ON FCARRID = PCARRID
    WHERE FCONNID = PCONNID
      AND P~CITYFROM = 'FRANKFURT'
      AND P~CITYTO   = 'NEW YORK'
      AND F~FLDATE BETWEEN '20010910' AND '20010920'
      AND FSEATSOCC < FSEATSMAX.
  WRITE: / DATE, CARRID, CONNID.
ENDSELECT.
Note
Since not all of the database systems supported by SAP use the standard syntax for ON conditions, the syntax has been restricted. It only allows those joins that produce the same results on all of the supported database systems:
Only a table or view may appear to the right of the JOIN operator, not another join expression.
Only AND is possible in the ON condition as a logical operator.
Each comparison in the ON condition must contain a field from the right-hand table.
If an outer join occurs in the FROM clause, all the ON conditions must contain at least one "real" JOIN condition (a condition that contains a field from tabref1 amd a field from tabref2.
Note
In some cases, '*' may be specified in the SELECT clause, and an internal table or work area is entered into the INTO clause (instead of a list of fields). If so, the fields are written to the target area from left to right in the order in which the tables appear in the FROM clause, according to the structure of each table work area. There can then be gaps between table work areas if you use an Alignment Request. For this reason, you should define the target work area with reference to the types of the database tables, not simply by counting the total number of fields. For an example, see below:
Variant 3
... FROM tabref1 LEFT [OUTER] JOIN tabref2 ON cond
Effect
Selects the data from the transparent database tables and/or views specified in tabref1 and tabref2. tabref1 und tabref2 both have either the same form as in variant 1 or are themselves join expressions. The keyword OUTER can be omitted. The database tables or views specified in tabref1 and tabref2 must be recognized by the ABAP-Dictionary.
In order to determine the result of a SELECT command where the FROM clause contains a left outer join, the database system creates a temporary table containing the lines that meet the ON condition. The remaining fields from the left-hand table (tabref1) are then added to this table, and their corresponding fields from the right-hand table are filled with ZERO values. The system then applies the WHERE condition to the table.
Left outer join between table 1 and table 2 where column D in both tables set the join condition:
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 |
    |--||||||||--|
Regards
Prabhu