Inner join Vs Outer join with ABAP code...?

Question

Inner join Vs Outer join with ABAP code...?

Answer 1

Inner Join means, it will not select that recor at all, unless there is a matching entry in the second table.
suppose table VBAK INNER join table VBAP on VBAKVBELN = VBAPVBELN.
In this case, if there are no entries in VBAP, the header entry also will not show up.
But in case of OUTER JOIN, even if there is no items, it will show the header entry(VBAK) with blank columns for fields  from item table.(VBAP)
here is one sample for inner join.
SELECT   A~EBELN
           A~EKORG
           A~EKGRP
           A~BSART
           A~LPONR
           A~LOEKZ
           A~LIFNR
           A~RESWK
           B~AEDAT
           B~WERKS
           B~MATNR
           B~MENGE
           B~EBELP
           B~ELIKZ
           B~PLIFZ
           B~PSTYP
           B~KNTTP
           B~MATKL
           B~ZZD_PLANT
           FROM EKKO AS A INNER JOIN EKPO AS B
           ON
           AEBELN = BEBELN
           INTO CORRESPONDING FIELDS OF TABLE T_DATA
           FOR ALL ENTRIES IN T_EKET
           WHERE
           A~EBELN EQ T_EKET-EBELN AND
           A~BSART EQ C_UBSTO      AND
           A~EKORG IN S_EKORG      AND
           A~EKGRP IN S_EKGRP      AND
           A~BSTYP EQ C_BSTYP      AND
           A~LOEKZ EQ SPACE        AND " Order not deleted
           A~RESWK IN S_RESWK      AND
           B~EBELN EQ T_EKET-EBELN AND
           B~EBELP EQ T_EKET-EBELP AND
           B~WERKS IN S_WERKS      AND
           B~MATNR IN S_MATNR      AND
           B~MATKL IN S_MATKL      AND
           B~LOEKZ EQ SPACE.           " Line item not deleted