Update
This commit is contained in:
danrega
182
11_Internal_Tables_Grouping.md
Normal file
182
11_Internal_Tables_Grouping.md
Normal file
@@ -0,0 +1,182 @@
|
||||
<a name="top"></a>
|
||||
|
||||
# Internal Tables: Grouping
|
||||
|
||||
- [Internal Tables: Grouping](#internal-tables-grouping)
|
||||
- [Introduction](#introduction)
|
||||
- [Grouping by One Column](#grouping-by-one-column)
|
||||
- [Grouping by More than One Column](#grouping-by-more-than-one-column)
|
||||
- [Group Key Binding when Grouping by One Column](#group-key-binding-when-grouping-by-one-column)
|
||||
- [Group Key Binding when Grouping by More than One Column](#group-key-binding-when-grouping-by-more-than-one-column)
|
||||
- [Executable Example](#executable-example)
|
||||
|
||||
|
||||
## Introduction
|
||||
|
||||
Similar to SQL's [`GROUP BY`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abapgroupby_clause.htm),
|
||||
there is also a [`GROUP BY`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_group_by.htm)
|
||||
for working with internal tables that can be used behind [`LOOP AT itab`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_variants.htm)
|
||||
or in the form [`IN GROUP`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenfor_in_group.htm)
|
||||
in a table iteration with
|
||||
[`FOR`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenfor_itab.htm).
|
||||
It replaces the clumsy group level processing with statements [`AT NEW ...`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abapat_itab.htm)
|
||||
that relies on the order of table columns and content that is sorted
|
||||
respectively.
|
||||
|
||||
Thi cheat sheet explains the grouping of internal tables step by step
|
||||
using a very simple case of an internal table `spfli_tab` that
|
||||
is filled with data from the database table `SPFLI`. The
|
||||
following steps show how the content of the internal table can be
|
||||
grouped using [`LOOP AT GROUP BY`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_group_by.htm).
|
||||
|
||||
## Grouping by One Column
|
||||
|
||||
The simplest form of grouping is by one column without explicitly
|
||||
specifying the output behavior of the group loop:
|
||||
|
||||
``` abap
|
||||
LOOP AT spfli_tab INTO wa
|
||||
GROUP BY wa-carrid.
|
||||
... wa-carrid ...
|
||||
ENDLOOP.
|
||||
```
|
||||
|
||||
Within the loop, there is access to the work area `wa`, in
|
||||
particular to the component `wa-carrid` that is used for
|
||||
grouping. The work area `wa` contains the first line of each
|
||||
group and represents the group in the loop. This is called
|
||||
representative binding.
|
||||
|
||||
To access the members of a group, a member loop can be inserted into the
|
||||
group loop:
|
||||
``` abap
|
||||
LOOP AT spfli_tab INTO wa
|
||||
GROUP BY wa-carrid.
|
||||
...
|
||||
LOOP AT GROUP wa INTO DATA(member).
|
||||
... member-... ...
|
||||
ENDLOOP.
|
||||
...
|
||||
ENDLOOP.
|
||||
```
|
||||
|
||||
The member loop is executed using the group represented by `wa`
|
||||
and its members are assigned to `member` and are available in
|
||||
the member loop.
|
||||
|
||||
<p align="right"><a href="#top">⬆️ back to top</a></p>
|
||||
|
||||
## Grouping by More than One Column
|
||||
|
||||
To group by more than just one criterion, a structured group key is
|
||||
defined as follows. In the simplest case, the grouping criteria are
|
||||
columns of the internal table:
|
||||
|
||||
``` abap
|
||||
LOOP AT spfli_tab INTO wa
|
||||
GROUP BY ( key1 = wa-carrid key2 = wa-airpfrom ).
|
||||
... wa-carrid ... wa-airpfrom ...
|
||||
ENDLOOP.
|
||||
```
|
||||
|
||||
This is also a representative binding in which the work area
|
||||
`wa` is reused in the group loop to access the group key.
|
||||
|
||||
To access the members of the groups, the exact same member loop can be
|
||||
inserted as when grouping by one column.
|
||||
|
||||
<p align="right"><a href="#top">⬆️ back to top</a></p>
|
||||
|
||||
## Group Key Binding when Grouping by One Column
|
||||
|
||||
By explicitly specifying an [output
|
||||
area](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_group_by_binding.htm)
|
||||
for the group key, a group key binding can be defined explicitly instead
|
||||
of the representative binding in which the output area of the group loop
|
||||
is reused:
|
||||
|
||||
``` abap
|
||||
LOOP AT spfli_tab INTO wa
|
||||
GROUP BY wa-carrid
|
||||
INTO DATA(key).
|
||||
... key ...
|
||||
ENDLOOP.
|
||||
```
|
||||
|
||||
The difference to the example with representative binding is the
|
||||
`INTO` addition after `GROUP BY`. Instead of reusing
|
||||
`wa`, an elementary data object `key` represents the
|
||||
group. This can be generated inline. The additions [`GROUP
|
||||
SIZE`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_group_by_key.htm),
|
||||
[`GROUP
|
||||
INDEX`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_group_by_key.htm),
|
||||
and [`WITHOUT
|
||||
MEMBERS`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_group_by.htm)
|
||||
can only be used in the group key binding, which gives it more functions
|
||||
than the representative binding. If these are not required, the
|
||||
representative binding can be used. The group key binding can also be
|
||||
used to make the use of the group key in the loop more explicit.
|
||||
|
||||
Inserting a member loop works in the same way as in the representative
|
||||
binding, with the difference that a group is now addressed by
|
||||
`key` instead of `wa`.
|
||||
|
||||
``` abap
|
||||
LOOP AT spfli_tab INTO wa
|
||||
GROUP BY wa-carrid
|
||||
INTO key.
|
||||
...
|
||||
LOOP AT GROUP key INTO member.
|
||||
... members ...
|
||||
ENDLOOP.
|
||||
...
|
||||
ENDLOOP.
|
||||
```
|
||||
|
||||
<p align="right"><a href="#top">⬆️ back to top</a></p>
|
||||
|
||||
## Group Key Binding when Grouping by More than One Column
|
||||
Finally, the group key binding for structured group keys:
|
||||
|
||||
``` abap
|
||||
LOOP AT spfli_tab INTO wa
|
||||
GROUP BY ( key1 = wa-carrid key2 = wa-airpfrom )
|
||||
INTO DATA(key).
|
||||
... key-key1 ... key-key2 ...
|
||||
ENDLOOP.
|
||||
```
|
||||
|
||||
Here, `key` is a structure with the components `key1`
|
||||
and `key2`. A member loop can be inserted in exactly the same
|
||||
way as when grouping by one column.
|
||||
|
||||
If the group members are not relevant, the addition [`NO
|
||||
MEMBERS`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_group_by.htm)
|
||||
can be used to save time and memory.
|
||||
|
||||
``` abap
|
||||
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.
|
||||
```
|
||||
|
||||
It is no longer possible to use a member loop here. Instead, the group
|
||||
key was enriched with optional components for further information using
|
||||
[`GROUP
|
||||
INDEX`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_group_by_key.htm)
|
||||
[`GROUP
|
||||
SIZE`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abaploop_at_itab_group_by_key.htm).
|
||||
|
||||
<p align="right"><a href="#top">⬆️ back to top</a></p>
|
||||
|
||||
## Executable Example
|
||||
|
||||
[zcl_demo_abap_sql_group_by](./src/zcl_demo_abap_sql_group_by.clas.abap)
|
||||
|
||||
> **💡 Note**<br>
|
||||
> - The steps to import and run the code are outlined [here](README.md#-getting-started-with-the-examples).
|
||||
> - [Disclaimer](README.md#%EF%B8%8F-disclaimer)
|
||||
Reference in New Issue
Block a user