Syntax of inner join

Question

hello sir,
             plz tell me the syntax of inner join for three tables.

Answer 1

Syntax
... [(] {dbtab_left [AS tabalias_left]} | join
{[INNER] JOIN}|{LEFT [OUTER] JOIN}
{dbtab_right [AS tabalias_right] ON join_cond} [)] ... .
Effect
The join syntax represents a recursively nestable join expression. A join expression consists of a left-hand and a right- hand side, which are joined either by means of [INNER] JOIN or LEFT [OUTER] JOIN . Depending on the type of join, a join expression can be either an inner ( INNER) or an outer (LEFT OUTER) join. Every join expression can be enclosed in round brackets. If a join expression is used, the SELECT command circumvents SAP buffering.
On the left-hand side, either a single database table, a view dbtab_left, or a join expression join can be specified. On the right-hand side, a single database table or a view dbtab_right as well as join conditions join_cond can be specified after ON. In this way, a maximum of 24 join expressions that join 25 database tables or views with each other can be specified after FROM.
AS can be used to specify an alternative table name tabalias for each of the specified database table names or for every view. A database table or a view can occur multiple times within a join expression and, in this case, have various alternative names.
The syntax of the join conditions join_cond is the same as that of the sql_cond conditions after the addition WHERE, with the following differences:
At least one comparison must be specified after ON.
Individual comparisons may be joined using AND only.
All comparisons must contain a column in the database table or the view dbtab_right on the right-hand side as an operand.
The following language elements may not be used: BETWEEN, LIKE, IN.
No sub-queries may be used.
For outer joins, only equality comparisons (=, EQ) are possible.
If an outer join occurs after FROM, the join condition of every join expression must contain at least one comparison between columns on the left-hand and the right-hand side.
In outer joins, all comparisons that contain columns as operands in the database table or the view dbtab_right on the right-hand side must be specified in the corresponding join condition. In the WHERE condition of the same SELECT command, these columns are not allowed as operands.
Resulting set for inner join
The inner join joins the columns of every selected line on the left- hand side with the columns of all lines on the right-hand side that jointly fulfil the join_cond condition. A line in the resulting set is created for every such line on the right-hand side. The content of the column on the left-hand side may be duplicated in this case. If none of the lines on the right-hand side fulfils the join_cond condition, no line is created in the resulting set.
Resulting set for outer join
The outer join basically creates the same resulting set as the inner join, with the difference that at least one line is created in the resulting set for every selected line on the left-hand side, even if no line on the right-hand side fulfils the join_cond condition. The columns on the right-hand side that do not fulfil the join_cond condition are filled with null values.
Example
Join the columns carrname, connid, fldate of the database tables scarr, spfli and sflight by means of two inner joins. A list is created of the flights from p_cityfr to p_cityto. Alternative names are used for every table.
PARAMETERS: p_cityfr TYPE spfli-cityfrom,
p_cityto TYPE spfli-cityto.
DATA: BEGIN OF wa,
fldate TYPE sflight-fldate,
carrname TYPE scarr-carrname,
connid TYPE spfli-connid,
END OF wa.
DATA itab LIKE SORTED TABLE OF wa
WITH UNIQUE KEY fldate carrname connid.
SELECT ccarrname pconnid f~fldate
INTO CORRESPONDING FIELDS OF TABLE itab
FROM ( ( scarr AS c
INNER JOIN spfli AS p ON pcarrid = ccarrid
AND p~cityfrom = p_cityfr
AND p~cityto = p_cityto )
INNER JOIN sflight AS f ON fcarrid = pcarrid
AND fconnid = pconnid ).
LOOP AT itab INTO wa.
WRITE: / wa-fldate, wa-carrname, wa-connid.
ENDLOOP.
Example
Join the columns carrid, carrname and connid of the database tables scarr and spfli using an outer join. The column connid is set to the null value for all flights that do not fly from p_cityfr. This null value is then converted to the appropriate initial value when it is transferred to the assigned data object. The LOOP returns all airlines that do not fly from p_cityfr.
PARAMETERS p_cityfr TYPE spfli-cityfrom.
DATA: BEGIN OF wa,
carrid TYPE scarr-carrid,
carrname TYPE scarr-carrname,
connid TYPE spfli-connid,
END OF wa,
itab LIKE SORTED TABLE OF wa
WITH NON-UNIQUE KEY carrid.
SELECT scarrid scarrname p~connid
INTO CORRESPONDING FIELDS OF TABLE itab
FROM scarr AS s
LEFT OUTER JOIN spfli AS p ON scarrid = pcarrid
AND p~cityfrom = p_cityfr.
LOOP AT itab INTO wa.
IF wa-connid = '0000'.
WRITE: / wa-carrid, wa-carrname.
ENDIF.
ENDLOOP.
we r using 2 type of joins in abap they are
1) inner join.
this will join 2 tables using an common fiend and return the result with field values wich are common in both the tables
itab1 itab2
a b c a d
1 2 3 1 5
2 3 4 3 6
after innerjoining itab1 n itab2 on field a we wil get the o/p as
a b c d
1 2 3 5
only common field is taken..
2)left outer join
here it wil work in opossite way it will give values whic are not common
itab1 itab2
a b c a d
1 2 3 1 5
2 3 4 3 6
after left outer joining itab1 n itab2 on field a we wil get the o/p as
a b c d
2 3 4
only fields which are not common is taken from the left table..other field(d here) wil be empty
I think it will help u.
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