Monthly Archives: March 2014
What about NULL
What is NULL? Is NULL a space? Is NULL a NULL string? NULL is unknown. If null is unknown then you can not do anything with null. You can not perform any operation on null: Y := 5+UNKNOWN then Y=UNKNOWN … Continue reading
Posted in Database Stuff
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Beyond the basic select statement: Using the WITH clause inline SUBQUERY
We looked at the with statement with embedded PL/SQL, now lets look at another use of the with statement. This time we are going to use it with embedded subqueries. Query A This query searches a stocks table, returns the … Continue reading
Beyond the basic select statement: Using the WITH clause inline PL/SQL
For years I used the basic select statement: SELECT A.C1, A.C2, B.C1, B.C2, <…> FROM TAB1 A, TAB2 B WHERE A.C1 = B.C1; Sometimes this basic select statement would not answer my question. You can make a select statement quite … Continue reading
Exploring the CBO
Lets start with a simple experiment on what the CBO can do with query optimization. We are going to build on the structure as we go to see if we can help out the CBO with more information. Test 1) … Continue reading
Posted in Cost Based Optimizer, Database Stuff
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