Most Popular query execution

Using Materialized Views to Alter Oracle Query Execution Paths

For a large database, a materialized view may offer several performance benefits. You can use materialized views to influence the optimizer to change the execution paths for queries. This feature, called query rewrite, enables the optimizer to use a materialized view in place of the table queried by the materialized view, even if the materialized […]

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Order of Query Execution in Oracle 12c

Here are the rules Oracle uses to execute each query, and the order in which execution takes place: Choose rows based on the WHERE clause. Group those rows together based on the GROUP BY clause. Calculate the results of the group functions for each group. Choose and eliminate groups based on the HAVING clause. Order […]

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Why Functionally Equivalent SQL Queries In Oracle May Not Be Equally Efficient

The inventor of the relational model, Dr. Edgar Codd, was of the opinion that “[r]equesting data by its properties is far more natural than devising a particular algorithm or sequence of operations for its retrieval. Thus, a calculus-oriented language provides a good target language for a more user-oriented source language” (“Relational Completeness of Data Base […]

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