If possible, convert the data in the driver table to ranges so a BETWEEN statement is used instead of and OR statement: FOR ALL ENTRIES IN i_tab
WHERE mykey >= i_tab-low and
mykey <= i_tab-high.
The plus:
- Small amount of data
- Mixing processing and reading of data
- Easy to code - and understand
The minus:
- Large amount of data
- when mixed processing isn’t needed
- Performance killer no. 1
The plus
- Very large amount of data
- Similar to Nested selects - when the accesses are planned by the programmer
- In some cases the fastest
- Not so memory critical
The minus
- Very difficult to program/understand
- Mixing processing and reading of data not possible
SELECT * FROM SBOOK.
CHECK: SBOOK-CARRID = 'LH' AND
SBOOK-CONNID = '0400'.
ENDSELECT.
SELECT * FROM SBOOK
WHERE CARRID = 'LH' AND
CONNID = '0400'.
ENDSELECT.
C4A = '000'.
SELECT * FROM T100
WHERE SPRSL = 'D' AND
ARBGB = '00'.
CHECK: T100-MSGNR > C4A.
C4A = T100-MSGNR.
ENDSELECT.
SELECT MAX( MSGNR ) FROM T100 INTO C4A
WHERE SPRSL = 'D' AND
ARBGB = '00'.
SELECT * FROM DD01L
WHERE DOMNAME LIKE 'CHAR%'
AND AS4LOCAL = 'A'.
SELECT SINGLE * FROM DD01T
WHERE DOMNAME = DD01L-DOMNAME
AND AS4LOCAL = 'A'
AND AS4VERS = DD01L-AS4VERS
AND DDLANGUAGE = SY-LANGU.
ENDSELECT.
SELECT * FROM DD01V
WHERE DOMNAME LIKE 'CHAR%'
AND DDLANGUAGE = SY-LANGU.
ENDSELECT.
SELECT * FROM T100
WHERE ARBGB = '00'
AND MSGNR = '999'.
ENDSELECT.
SELECT * FROM T002.
SELECT * FROM T100
WHERE SPRSL = T002-SPRAS
AND ARBGB = '00'
AND MSGNR = '999'.
ENDSELECT.
ENDSELECT.
REFRESH X006.
SELECT * FROM T006 INTO X006.
APPEND X006.
ENDSELECT
SELECT * FROM T006 INTO TABLE X006.
SELECT * FROM DD01L
WHERE DOMNAME LIKE 'CHAR%'
AND AS4LOCAL = 'A'.
ENDSELECT
SELECT DOMNAME FROM DD01L
INTO DD01L-DOMNAME
WHERE DOMNAME LIKE 'CHAR%'
AND AS4LOCAL = 'A'.
ENDSELECT
LOOP AT TAB.
CHECK TAB-K = KVAL.
" ...
ENDLOOP.
LOOP AT TAB WHERE K = KVAL.
" ...
ENDLOOP.
REFRESH TAB_DEST.
LOOP AT TAB_SRC INTO TAB_DEST.
APPEND TAB_DEST.
ENDLOOP.
TAB_DEST[] = TAB_SRC[].
LOOP AT TAB.
IF TAB-FLAG IS INITIAL.
TAB-FLAG = 'X'.
ENDIF.
MODIFY TAB.
ENDLOOP.
TAB-FLAG = 'X'.
MODIFY TAB TRANSPORTING FLAG
WHERE FLAG IS INITIAL.
DO 101 TIMES.
DELETE TAB_DEST INDEX 450.
ENDDO.
DELETE TAB_DEST FROM 450 TO 550.
READ TABLE TAB WITH KEY K = 'X'.
READ TABLE TAB WITH KEY K = 'X' BINARY SEARCH.
DESCRIBE TABLE: TAB1 LINES L1,
TAB2 LINES L2.
IF L1 <> L2.
TAB_DIFFERENT = 'X'.
ELSE.
TAB_DIFFERENT = SPACE.
LOOP
AT TAB1.
READ TABLE TAB2 INDEX SY-TABIX.
IF TAB1 <> TAB2.
TAB_DIFFERENT = 'X'. EXIT.
ENDIF.
ENDLOOP.
ENDIF.
IF TAB_DIFFERENT = SPACE.
" ...
ENDIF.
IF TAB1[] = TAB2[].
" ...
ENDIF.
LOOP AT TAB.
TAB-DATE = SY-DATUM.
MODIFY TAB.
ENDLOOP.
WA-DATE = SY-DATUM.
LOOP AT TAB.
MODIFY TAB FROM WA TRANSPORTING DATE.
ENDLOOP.
LOOP AT TAB_SRC.
APPEND TAB_SRC TO TAB_DEST.
ENDLOOP
APPEND LINES OF TAB_SRC TO TAB_DEST.
LOOP AT TAB_DEST WHERE K = KVAL.
DELETE TAB_DEST.
ENDLOOP
DELETE TAB_DEST WHERE K = KVAL.
· The runtime analysis (SE30)
· SQL Trace (ST05)
· Tips and Tricks tool
· The performance database
Using table buffering
Using buffered tables improves the performance considerably. Note that in some cases a statement can not be used with a buffered table, so when using these statements the buffer will be bypassed. These statements are:
- Select DISTINCT
- ORDER BY / GROUP BY / HAVING clause
- Any WHERE clause that contains a sub query or IS NULL expression
- JOIN s
- A SELECT... FOR UPDATE
If you wan t to explicitly bypass the buffer, use the BYPASS BUFFER addition to the SELECT clause.
Use the ABAP SORT Clause Instead of ORDER BY
The ORDER BY clause is executed on the database server while the ABAP SORT statement is executed on the application server. The database server will usually be the bottleneck, so sometimes it is better to move the sort from the database server to the application server.
If you are not sorting by the primary key ( E.g. using the ORDER BY PRIMARY key statement) but are sorting by another key, it could be better to use the ABAP SORT statement to sort the data in an internal table. Note however that for very large result sets it might not be a feasible solution and you would want to let the database server sort it.
Avoid the SELECT DISTINCT Statement
As with the ORDER BY clause it could be better to avoid using SELECT DISTINCT, if some of the fields are not part of an index. Instead use ABAP SORT + DELETE ADJACENT DUPLICATES on an internal table, to delete duplicate rows.
