what does non-unique key do ? I think unique key can be used for selecting a unique row from a internal table object, and also used for sorting . but why is non-unique key there if I can only select row by index ( which is stadard table)?
thanks very much!
Suren Anakala replied
Hi bo zhang
As you know unique keys are used as primary indexes in the where clause of a select statement.
To have secondary indexes in the where clause, we've to make use of non-unique keys.
But in performance view, we should not use, since as it is a non-unique, we come across many duplicates, so generally we use it as the situation demands.
At max., we can make 16 secondary indexes.
Here i like to differentiate b/w index and keys to clear the confusion. At the creation of database table through se11, we've to position the unique key fields at top of the table fields to clarify the entries to be identified.
About Indexes, after activating the table in se11, the system implicitly creates indexes for the table based on primary keys and secondary indexes based on non-unique keys.
For further doubts feel free to contact me.
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