Configuring Oracle for learning purpose in Laptop Hi all, I would like to configure Oracle11g in my laptop for learning purpose. Could you just tell me as to how to simulate a pl-sql development environment in home laptop?
An additional one adding the unique column in-between: And now for access with the unique column as a key: Here are some interesting stats: Of course, the non-covering index is smaller but will need table access to query additional column.
The index with 3 columns is the largest. However for some queries you may cover only the filter predicates and go to the table for projection.
To understand the change in clustering factor we must go deeper on Oracle index key and data implementation. Non-unique indexes are a special case.
Actually, Oracle implements only unique key indexes. When the indexed columns are not unique, the ROWID is stored on the key part of the index entry, and there is no data part. They are smaller because the branch does not have to store the full value of all columns in order to identify one leaf block.
Then, only the first bytes are needed and not the full 80 bytes of them. The full 80 bytes must be stored, and the rowid in addition to it. When the indexed column has only unique values, there is no need to store more in the branches not the additional columns, not the rowid and only 12 bytes are needed here on average: When creating an index, or adding columns for covering index, and you have the choice of column order, then try to have their first bytes selective enough so that the branch needs only a small substring to identify each leaf block or lower level branches.
Block dumps If you want to see the details about the branch length, here are some info from block dumps. I got them with the following: However, this may require thinking about the order of columns, mainly: Read this tread, answers and links from Richard Foote:Power Ranking Oracle APEX New Features – March.
As of March 12, we now know rather than , the new version of APEX will be March 12th also gave us . This Oracle RMAN training was designed by Robert Freeman, an acknowledged leader in Oracle database administration and author of more than 6 bestselling Oracle administration books.
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