In my blog ABAP News for 7.40, SP08 - GROUP BY for Interna... | SCN I introduced the GROUP BY addition for LOOP AT for internal tables.
Since there seems to be some confusion about the syntax and its meaning, let us approach the grouping of internal tables step by step using a very simple case and you will see that it isn't that complicated at all. I also attached the full text of a program, that executes the following steps and produces some output.
Say, you have an internal table spfli_tab TYPE TABLE OF spfli filled with data from database table SPFLI (what else ...).
Step 1, Grouping by one column
The most simple thing you can do is grouping by one column:
LOOP AT spfli_tab INTO wa
GROUP BY wa-carrid.
... wa-carrid ...
ENDLOOP.
Inside the loop you can access wa, especially wa-carrid. wa contains the first line of each group that is created by GROUP BY. This is called representative binding. Inside the loop wa represents a group.
In order to access the members of each group, you add a member loop:
LOOP AT spfli_tab INTO wa
GROUP BY wa-carrid.
...
LOOP AT GROUP wa INTO DATA(member).
... member-... ...
ENDLOOP.
...
ENDLOOP.
member is a structure with the line type of spfli_tab and contains the members of each group.
Step 2, Grouping by more than one column
If you want to group by more than one grouping criterion (columns in the most simple case), you write:
LOOP AT spfli_tab INTO wa
GROUP BY ( key1 = wa-carrid key2 = wa-airpfrom ).
... wa-carrid ... wa-airpfrom ...
ENDLOOP.
In this case, you construct a structured group key. In the case of representative binding shown here, wa is reused for accessing the group key inside the loop.
In order to access the members of the groups, you can add exactly the same member loop as in step 1 above.
Step 3, Group key binding for grouping by one column
Besides the representative binding, where the INTO-clause of LOOP AT is reused for accessing the group, you can define a group key binding:
LOOP AT spfli_tab INTO wa
GROUP BY wa-carrid
INTO DATA(key).
... key ...
ENDLOOP.
Not too different from step 1 above, eh? Instead of reusing wa, you use an elementary data object key that for convenience is declared inline here. Group key binding offers some more functionality compared to representative binding (additions WITHOUT MEMBERS, GROUP SIZE, GROUP INDEX). If you don't need those, you can stay with representative binding. Nevertheless, I myself always prefer group key binding, since it makes the group key more explicit. But that's a question of taste.
Inserting the member loop works as before:
LOOP AT spfli_tab INTO wa
GROUP BY WA-CARRID
INTO DATA(key).
...
LOOP AT GROUP key INTO member.
... members ...
ENDLOOP.
...
ENDLOOP.
Note, that you access the group using the name key now.
Step 4, Group key binding for grouping by more than one column
Last but not least, group key binding for structured group keys:
LOOP AT spfli_tab INTO wa
GROUP BY ( key1 = wa-carrid key2 = wa-airpfrom )
INTO DATA(key).
... key-key1 ... key-key2 ...
ENDLOOP.
Now, key is a structure with the components key1 and key2. The member loop can be added exactly as in step 3.
If you aren't interested in the members, you can use the NO MEMBERS addition in order to save some run time and some memory. E.g.
LOOP AT spfli_tab INTO wa
GROUP BY ( key1 = wa-carrid key2 = wa-airpfrom
index = GROUP INDEX size = GROUP SIZE )
WITHOUT MEMBERS
INTO DATA(key).
... key-key1 ... key-key2 ... key-index ... key-size ...
ENDLOOP.
A member loop is not possible here. But key is enriched with some predefiined optional components for additional informations.
Conclusion
Not too complicated, or?
Having understood these simple facts, you can go on, read the documentation, and do more complicated things, e.g. exploiting the fact that you can use expressions for the RHS of the group key definitions or using FOR expressions instead of LOOP AT.
