Range-&-Hash-partitioning tables partitioning key columns - Oracle Indexes and Partitioned Tables

Q.  How many partitioning keys columns are specified for range-and-hash-partitioning tables?
- Published on 27 Jul 15

a. 18
b. 14
c. 16
d. 17



  • Nirja Shah   -Posted on 29 Sep 15
    - For range- and hash-partitioned tables, you can specify up to 16 partitioning key columns.

    - Multicolumn partitioning should be used when the partitioning key is composed of several columns and subsequent columns define a higher granularity than the preceding ones.

    - The most common scenario is a decomposed DATE or TIMESTAMP key, consisting of separated columns, for year, month, and day.

    - In evaluating multicolumn partitioning keys, the database uses the second value only if the first value cannot uniquely identify a single target partition, and uses the third value only if the first and second do not determine the correct partition, and so forth.

    - A value cannot determine the correct partition only when a partition bound exactly matches that value and the same bound is defined for the next partition.

    - The nth column will therefore be investigated only when all previous (n-1) values of the multicolumn key exactly match the (n-1) bounds of a partition.

    - A second column, for example, will be evaluated only if the first column exactly matches the partition boundary value.

    - If all column values exactly match all of the bound values for a partition, the database will determine that the row does not fit in this partition and will consider the next partition for a match.

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