Flemming Frandsen wrote
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>On Tue, 27 Nov 2001, [iso-8859-1] Alberto Barcelón wrote:
>
>> CREATE TABLE test (
>> id INTEGER NOT NULL DEFAULT seqtest.NEXTVAL,
>> name CHAR(20)
>> )
>
>Just a warning: It is extremely bad to not declare the primary key as SAP
>DB then creates the default primary from all columns in the table:
??? unfortunately I have to say: that is not true. True is:
If no user-defined primary key is specified, SAP DB appends the column
SYSKEY CHAR (8) BYTE
to the table and this appended column is the primary key!!
BTW: keys can be up to 1024 bytes in length, rows up to around 8000 bytes,
therefore the above
would not work
>1) You get tablescans to find stuff by id.
If id is neither keycolumn nor indexed column, a WHERE id = 4711 has no
other chance than to use
a tablescan. In case you use the SAP DB implicit primary key SYSKEY, then
the above WHERE-
clause had to use a tablescan. If you specify an index on id, that index
will be used in this case.
>2) You get slow updates to the name column because the index needs to be
>updated.
See above, there is no implicit index (part of index) on name if you do not
specify a primary key.
Therefore: don't worry about this.
Elke
SAP Labs Berlin
