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= 7 days or newer |
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Documentation
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This is part 1 of a series of articles designed to introduce Oracle's PL/SQL to you and explain how it can be used to improve query performance and genrally make life easier for Oracle developers.
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Sometimes you need a table with N rows as a seed for a dataset. The content of the records doesn't matter. They just need to be there. For example, suppose you need a table with enough records to create a record for each day of this year, how would you go about it?
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Scripts to make Oracle behave as if it has an auto-number. Uses a sequence and a trigger.
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Generally, sequences can be cached with cache values as high as 200 in RAC. This is much higher than for a regular Oracle instance. If there is insufficient caching, then contention can result which will show up as an increase in service times. If there are performance problems due to sequences, then examine the row cache locks statistics in the v$system_eventview to determine whether the problem is due to the use of Oracle sequences.
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Oracle sequential read disk I/O tuning
Oracle Tips by Burleson Consulting
Updated October 29, 2007
Also, see my related important notes on tuning full-scan I/O.
Because all Oracle databases retrieve and store data, the relative cost of physical disk access is an important topic. In Oracle, we see two types of data block access:
db file sequential read—A single-block read (i.e., index fetch by ROWID)
db file scattered read—A multiblock read (a full-table scan, OPQ, sorting)
Physical disk speed is an important factor in weighing these costs. Faster disk access speeds can reduce the costs of a full-table scan vs. single block reads to a negligible level.
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This article is introduces Oracle's CUBE and ROLLUP extensions to the GROUP BY clause. The schema and sample data population scripts that accompany the discussion can be accessed here.
The usual way to aggregate data in relational databases is via the SQL group by clause. A limitation of this method is that one cannot get higher level aggregations within a single statement.
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Here are some useful SQL tricks and little known FAQs, tested on an Oracle database.
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So what's this business with Oracle allowing programmers to put programs in databases? That's right. They're called Oracle stored procedures, and they're quite useful. Mooh the Cow walks you through writing, creating, debugging, and deleting a procedure.
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A complete listing of oracle error messages categorized in sequential groups.
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In Oracle 9i, you can use the case statement within an SQL statement. It has the functionality of an IF-THEN-ELSE statement.
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