Lets discuss some good practices of coding

[ujjwal16]

This blog will help folks who just on-boarded for ABAP in understanding the codes in line with it.

Note: 1st block of code indicates incorrect way of coding. Codes that follow the golden rules are written just after that.

1. Having small result sets

1.1 WHERE condition

Requirement: Fetch customers whose customer type is 'B'.

DATA : lv_id TYPE scustom-id,

       lv_name TYPE scustom-name,

       lv_discount TYPE scustom-discount,

       lv_custtype TYPE scustom-custtype.

• Bad Practice

SELECT id name discount custtype FROM scustom

INTO (lv_id, lv_name, lv_discount, lv_custtype).

IF lv_custtype = 'B'.

WRITE : / lv_id, lv_name, lv_discount, lv_custtype.

ENDIF.

ENDSELECT.

• Good Practice

TYPES: BEGIN OF ty_scustom,

id       TYPE S_CUSTOMER,

name     TYPE S_CUSTNAME,

discount TYPE S_DISCOUNT,

custtype TYPE S_CUSTTYPE,

       END OF ty_scustom.



DATA: it_scuctom TYPE TABLE OF ty_scustom,

      wa_scustom TYPE ty_scustom.

SELECT id name discount custtype FROM scustom

INTO TABLE it_scustom   

WHERE custtype = 'B'.

LOOP AT it_scustom INTO wa_scustom.

WRITE : / wa_scustom-id, wa_scustom-name, 

          wa_scustom-discount, wa_scustom-custtype.

ENDLOOP.

Reason: Fetching filtered data is better than fetching the entire data set and then filtering it.

1.2 HAVING clause

Requirement: Fetch details of flights having the minimum seat occupancy. The minimum seat occupancy should be greater than zero.

DATA: lv_sflight TYPE sflight,

      lv_min     TYPE sflight-seatsocc.

• Bad Practice

SELECT carrid connid MIN( seatsocc ) FROM sflight

INTO (lv_sflight-carrid, lv_sflight-connid, lv_min)

GROUP BY carrid connid.

IF lv_min > 0.

WRITE:/ lv_sflight-carrid, lv_sflight-connid, lv_min.

ENDIF.

ENDSELECT.

• Good Practice

TYPES: BEGIN OF ty_sflight,

carrid   TYPE S_CARR_ID,

connid   TYPE S_CONN_ID,

seatsocc TYPE S_SEATSOCC,

       END OF ty_sflight.



DATA: it_sflight TYPE TABLE OF ty_sflight,

      wa_sflight TYPE ty_sflight.

SELECT carrid connid MIN( seatsocc ) FROM sflight

INTO TABLE it_sflight

GROUP BY carrid connid 

HAVING MIN( seatsocc ) > 0.

LOOP AT it_sflight INTO wa_sflight.

WRITE:/ wa_sflight-carrid, wa_sflight-connid, wa_sflight-min_socc.

END LOOP.

Reason: Do the calculation in the select query itself

1.3 Transferring required rows

Requirement: Fetch details

DATA: lt_scustom TYPE TABLE OF scustom,

      lw_scustom TYPE scustom.

• Bad Practice

SELECT id name discount custtype FROM scustom

INTO CORRESPONDING FIELDS OF TABLE lt_scustom

WHERE country = 'DE'.

DELETE lt_scustom WHERE custtype = 'P'.

LOOP AT lt_scustom INTO lw_scustom.

WRITE: / lw_scustom -id, lw_scustom -name, 

         lw_scustom-discount, lw_scustom -custtype.

ENDLOOP.

• Good Practice

SELECT id name discount custtype FROM scustom

INTO CORRESPONDING FIELDS OF TABLE lt_scustom

WHERE country = 'DE' AND custtype <> 'P'.

LOOP AT lt_scustom INTO lw_scustom.

WRITE: / lw_scustom-id, lw_scustom-name, 

         lw_scustom-discount, lw_scustom-custtype.

ENDLOOP.

Reason: Fetching required rows is better than fetching the entire data set and then delete the unwanted rows

2. Having small transferred data sets

2.1 DISTINCT clause

Requirement: Fetch distinct details of customers who avail discounts

DATA : lt_scustom TYPE TABLE OF scustom,

       lw_scustom TYPE scustom.

• Bad Practice

SELECT custtype discount FROM scustom

INTO CORRESPONDING FIELDS OF TABLE lt_scustom

WHERE discount > 0

ORDER BY custtype discount DESCENDING.

DELETE ADJACENT DUPLICATES FROM lt_scustom.

LOOP AT lt_scustom INTO lw_scustom.

WRITE : / lw_scustom-id, lw_scustom-discount.

ENDLOOP.

• Good Practice

SELECT DISTINCT custtype discount FROM scustom 

INTO CORRESPONDING FIELDS OF TABLE lt_scustom

WHERE discount > 0

ORDER BY custtype discount DESCENDING.

LOOP AT lt_scustom INTO lw_scustom.

WRITE : / lw_scustom-id, lw_scustom-discount.

ENDLOOP.

2.2 Using aggregate functions

Requirement: Display the total number of seats reserved in an airline in any given year

DATA : lv_sum      TYPE sflight-seatsocc,

       lv_seatsocc TYPE sflight-seatsocc.

• Bad Practice

SELECT seatsocc FROM sflight 

INTO lv_seatsocc

WHERE carrid = 'LH'AND fldate LIKE '2013 %'.

lv_sum = lv_sum + lv_seatsocc.

ENDSELECT.

WRITE : / lv_sum.

• Good Practice

SELECT SUM( seatsocc )FROM sflight 

INTO lv_sum

WHERE carrid = 'LH'AND fldate LIKE '2013 %'.

WRITE : / lv_sum.

2.3 Changing only required columns

Requirement: Change the connection number of a specific flight

DATA : lw_book TYPE sbook.

• Bad Practice

SELECT * FROM sbook

INTO lw_book

WHERE carrid = 'LH'AND connid = '0400'AND fldate >= '20160101'.

lw_book-connid = '0500'.

UPDATE sbook FROM lw_book.ENDSELECT.

• Good Practice

UPDATE sbookSET connid ='0500'

WHERE carrid = 'LH' AND connid = '0400' AND fldate >= '20160101'.

3. Reducing number of queries

3.1 Using set operations instead of individual operations

Requirement: Insert a record into the table SBOOK

• Bad Practice

LOOP AT it_sbook INTO lw_sbook.

INSERT INTO sbook VALUES lw_sbook.

ENDLOOP.

• Good Practice

INSERT sbook FROM TABLE lt_sbook.

3.2 Avoiding multiple accesses

Requirement: Delete details of flights with carrier ID AA and connection ID 17

• Bad Practice

SELECT SINGLE * FROM sflight

INTO lv_sflight WHERE carrid = 'AA' AND connid = '0017'.

IF sy-subrc EQ 0.

DELETE FROM sflight WHERE carrid = 'AA' AND connid = '0017'.

IF sy-subrc EQ 0.

COMMIT WORK.

ENDIF.

ENDIF.

• Good Practice

DELETE FROM sflight 

WHERE carrid = 'AA' AND connid = '0017'.

IF sy-subrc EQ 0.

COMMIT WORK.

ENDIF.

Reason: Delete data in the repository directly instead of fetching the dataset and then deleting it

3.3 Avoiding SELECT inside LOOPs

Requirement: Fetch details

• Bad Practice

LOOP AT lt_sflight INTO lw_sflight.

SELECT SINGLE bookid customid FROM sbook

INTO lw_sbook

WHERE carrid = lv_sflight-carrid AND connid = lv_sflight-connid

AND fldate = lv_sflight-fldate.

WRITE : / lv_sflight-carrid, lv_sflight-connid, lv_sflight-fldate,

          lv_sbook-bookid, lv_sbook-customid.

ENDLOOP.

• Good Practice

IF lt_sflight IS NOT INITIAL.

SELECT SINGLE bookid customid FROM sbook

INTO CORRESPONDING FIELDS OF TABLE lt_sbook

FOR ALL ENTRIES IN lt_sflight

WHERE carrid = lv_sflight-carrid AND connid = lv_sflight-connid

  AND fldate = lv_sflight-fldate.

ENDIF.