Top "Sql-execution-plan" questions

A execution, or query plan, is the breakdown of steps the database engine uses to get a result.

Will my index be used if all columns are not used?

I have an index on columns A, B, C, D of table T I have a query that pulls from …

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SQL Queries, execution plans and "Parallelism"

So I'm (still) going through some slow legacy sql views used to do calculate some averages and standarddeviations on a (…

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How do I use EXPLAIN to *predict* performance of a MySQL query?

I'm helping maintain a program that's essentially a friendly read-only front-end for a big and complicated MySQL database -- the …

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Are execution plan for functions cached in SQL server?

Can any body help me in understanding if the execution plan for functions cached in SQL server? Any online resource …

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When does the Oracle CBO choose to execute a "merge join cartesian" operation?

From time to time, Oracle seems to prefer a MERGE JOIN CARTESIAN operation over a regular MERGE JOIN. Knowing the …

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SQL Developer explain plan broken

Trying to generate an explain plan in SQL Developer, the program puts up a message box with title "failed to …

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SQL function very slow compared to query without function wrapper

I have this PostgreSQL 9.4 query that runs very fast (~12ms): SELECT auth_web_events.id, auth_web_events.time_stamp, …

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Does altering a stored procedure expire cached execution plans?

Does executing a ALTER PROCEDURE statement for a stored procedure cause all cached execution plans for that stored procedure to …

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