Using Histograms on Evenly Distributed Values
A quick demo … here's a script … drop table demo_hist / create table demo_hist as select floor(rownum/5) rn,do.* from dba_objects do / begin dbms_stats.gather_table_stats ( ownname => user, tabname...
View ArticleUpdate on Histograms
OK, that was a bad example. Here's a new approach. When the Oracle documentation talks about skewed values they are referring to particular values in a column occuring with significantly different...
View ArticleWriting Good SQL
This is prompted by a question asked by eastmael at the Oracle DBA Forum — "what I'd like to accomplish are optimized SQL statements … do you guys have any tips, links, or resources that could help me...
View ArticleStatistics By Block Sampling
If you're just joining us, I'd suggest that you scroll down and read the original article then the follow-ups from the bottom upwards. Update 03 Jun 2005 Another consideration raised, on the uniformity...
View ArticleDates as Key Values: Natural or Synthetic?
Here's a question: when deciding whether to use a date datatype as a key value, why does there seem to be some consensus that it is OK to do so, even in situations where the same person would not...
View ArticleDesigns That Balance ETL and Report Performance
It seems to me that there is sometimes a very difficult balance to strike, between optimizing the structure of a database for fast and convenient ETL loading and fast and convenient report querying....
View ArticleORA-12034: materialized view log younger than last refresh
Dabblers in the art of the materialisation of views may be used to seeing this error message, and it's often a portent of doom. Metalink Note 204127.1 tackles it head on with a list of possible causes,...
View ArticlePredicate Pushing And Analytic Functions
I'm sure that there must be a fair number of Oracle professionals who carry around in their heads a little score card of some of their best tuning results ever … hopefully, at least, 'cos otherwise I'm...
View ArticleMy Dishwasher is List Partitioned
My dishwasher has two levels in it. The bottom level is for plates and Large Things, the top level is for cups and Small Things, and there is a removable cutlery partition attached to the door. If I...
View ArticleThe Three Pillars of Oracle Data Warehousing
Introduction This is a basic topic for Oracle data warehousing beginners, based on some ideas that I’m hoping will stop buzzing round in my head if I commit them to virtual paper. There are three...
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