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Processing a table tuning



 
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PostPosted: Tue Sep 11, 2007 7:06 pm    Post subject: Processing a table tuning Reply with quote

1 Always check the driver internal tables is not empty, while using FOR ALL ENTRIES
You can only use FOR ALL ENTRIES IN ...WHERE ...in a SELECT statement. SELECT ... FOR ALL ENTRIES IN itab WHERE cond returns the union of the solution sets of all SELECT statements that would result if you wrote a separate statement for each line of the internal table replacing the symbol itab-f with the corresponding value of component f in the WHERE condition.Duplicates are discarded from the result set. If the internal table itab does not contain any entries, the system treats the statement as though there were no WHERE cond condition, and selects all records (in the current client).
For example:
SELECT * FROM sflight INTO wa_sflight
FOR ALL ENTRIES IN ftab
WHERE CARRID = ftab-carrid AND
CONNID = ftab-connid AND
fldate = '20010228'.
This condition, return all entries of the sflight

2 Avoid for all entries in JOINS
3 Try to avoid joins and use FOR ALL ENTRIES.
4 Try to restrict the joins to 1 level only ie only for 2 tables
5 Avoid using Select *.
6 Avoid having multiple Selects from the same table in the same object.
7 Try to minimize the number of variables to save memory.
8 The sequence of fields in 'where clause' must be as per primary/secondary index ( if any)
9 Avoid creation of index as far as possible
10 Avoid operators like <>, > , < & like % in where clause conditions
11 Avoid select/select single statements in loops.
12 Try to use 'binary search' in READ internal table. Ensure table is sorted before using BINARY SEARCH.
13 Avoid using aggregate functions (SUM, MAX etc) in selects ( GROUP BY , HAVING,)
14 Avoid using ORDER BY in selects
15 Avoid Nested Selects
16 Avoid Nested Loops of Internal Tables
17 Try to use FIELD SYMBOLS.
18 Try to avoid into Corresponding Fields of
19 Avoid using Select Distinct, Use DELETE ADJACENT.
20 Use hashed tables instead of standard tables. They are faster.
21 Avoid the use of collect as much as you can.
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