Instead of
selecting all the data and doing the processing during the
selection, it is advisable to restrict the data to the selection
criteria itself, rather than filtering it out using the ABAP code.
Not
recommended
Select * from zflight.
Check : zflight-airln = ‘LF’ and zflight-fligh = ‘BW222’.
Endselect.
Recommended
Select * from zflight where airln = ‘LF’ and fligh = ‘222’.
Endselect.
One more
point to be noted here is of the select *. Often this is a lazy
coding practice. When a programmer gives select * even if one or two
fields are to be selected, this can significantly slow the program
and put unnecessary load on the entire system. When the application
server sends this request to the database server, and the database
server has to pass on the entire structure for each row back to the
application server. This consumes both CPU and networking resources,
especially for large structures.
Thus it is
advisable to select only those fields that are needed, so that the
database server passes only a small amount of data back.
Also it is
advisable to avoid selecting the data fields into local variables as
this also puts unnecessary load on the server. Instead attempt must
be made to select the fields into an internal table.
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