As a group, having limited work

Question

Can someone explain how the working group + + + restriction works? MySQL query:

    SELECT
        id,
        avg(sal)
    FROM
        StreamData 
    WHERE
        ...
    GROUP BY
        id 
    HAVING
        avg(sal)>=10.0 
        AND avg(sal)<=50.0   
    LIMIT 100

A request without restrictions and availability of offers is executed within 7 seconds, with a restriction - instantly, if the condition covers a large amount of data or ~ 7 seconds otherwise. The documentation says that the limit is executed after that after the group, this means that the request should always be executed within ~ 7 seconds. Please help figure out what is limited by the LIMIT clause.

Answer 1

LIMIT 100 MySQL 100 . , Java, - , MySQL . , LIMIT 100 .

Answer 2

SQL:

• (FROM, JOIN)
• (WHERE)
• ( , , GROUP BY)
• (HAVING)
• (LIMIT, OFFSET)

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Answer 3

MySQL , , SQL_CALC_FOUND_ROWS. SELECT FOUND_ROWS(). 13.14 " ".

http://dev.mysql.com/doc/refman/5.7/en/limit-optimization.html

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Answer 4

 SELECT
        id,
        avg(sal)
    FROM
        StreamData 
    WHERE
        ...
    GROUP BY
        id 
    HAVING
    avg(sal)>=10.0 
    AND avg(sal)<=50.0   
LIMIT 100