Suboptimal Sort Calculation
Beware of the suboptimal sort cost calculation in SQL Server. Comparison with Oracle included. Continue Reading
Comparison Oracle-SQL Server
Comparing TSQL and PL/SQL Performance
Why Oracle outperforms SQL Server Continue Reading
Correlated Subqueries in the SELECT Clause (2)
Examples where Oracle optimizer doesn’t unnest subqueries in the SELECT clause Continue Reading
Correlated Subqueries in the SELECT Clause
How Oracle and SQL Server optimize correlated subqueries in the SELECT clause with an example how to manually optimize such queries for Oracle. Continue Reading
SQL Server Extended Events Trace Overhead
Measuring Extended Events Trace overhead and correctly interpreting the trace information. Continue Reading
Cardinality Estimation for “MINUS” Operator
Mind inaccurate cardinality estimations when using MINUS operator in subqueries. Continue Reading
Bind Variable Peeking vs. Parameter Sniffing
Comparison of bind variable peeking in Oracle with parameter sniffing in SQL Server Continue Reading
Comparison of a Cardinality Estimate in Oracle and SQL Server
This blog post is a short observation on assumptions that Oracle and SQL server optimizers make for estimating cardinality of a rowset obtained after applying an equality predicate which contains different columns of the same table. Continue Reading
Index Organized Table vs. Clustered Index
Comparing efficiency of IOT in Oracle with Clustered Index in SQL Server. Continue Reading
Disjunctive Subquery Optimization
Disjunctive subqueries are the subqueries which are applied to the or operator. Alternatively, these queries can be rewritten to use the union all operator which may be a more efficient way to retrieve the records from the database. This blog post compares the efficiency of SQL Server and Oracle optimizer when dealing with the transformations of disjunctive subqueries.
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