Mysql query, question about speed of execution

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Hello! I want to ask you, what SQL query will be execute faster, when i specify table fields that i wish to select or when i write only LEFT JOIN, without cpecify it?

Posted 8-May-13 11:10am

Jardin1

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Richard C Bishop 8-May-13 17:12pm

You have not provided any queries to compare. How are we supposed to tell you which one is faster? Besides, there are far too many factors that go into play when a query is executed to give you any accurate answer.

Jardin1 8-May-13 17:18pm

For example:

SELECT Drivers.name, Drivers.ID Drivers.year, Cars.year, Cars.type, Cars.Id_Driver
FROM Drivers AS D
LEFT JOIN Cars ON D.ID = C.Id_Driver
WHERE ...
_______
OR Query is:
SELECT *
FROM Drivers AS D
LEFT JOIN Cars ON D.ID = C.Id_Driver
WHERE ...
_______

Sudhakar Shinde 10-May-13 1:51am

Both the queries will take similar time since there is difference of columns you are selecting. Please check whether above mentioned query works properly.

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**R. Giskard Reventlov** · Answer 1 · 2013-05-08T11:36:00

Given that you have added an example I believe the first query should execute faster, all things being equal. You should place indexed fields left most.

You could also try using MySql's tools to evaluate speed of execution (I haven't used MySql for a long time so don't recall what tools are available for that purpose).