Sql-server – get an equivalent query for this Not in Query

aggregateoptimizationperformancequery-performancesql servertime

SELECT ID FROM dbo.SomeTable
            WHERE ID not in
            (
                SELECT MIN(ID)
                FROM dbo.SomeTable
                GROUP BY SystemNo
            )

As this query is taking very long (more than a minute) to get executed. I guess "IN" is the culprit for this. I would like a query which yield same result but with most efficient time.

Best Answer

You don't select those ids that are minimum in their systemno group so you select only those that have a lower id in their group:

SELECT id FROM dbo.SomeTable st1
WHERE EXISTS
  (
    SELECT *
    FROM dbo.SomeTable st2
    WHERE st1.SystemNo = st2.SystemNo AND st2.id < st1.i
  )

Related Solutions

Mysql – How to optimize this MySQL query further

After looking over the query, the tables, and the WHERE AND GROUP BY clauses, I recommend the following:

Recommendation #1) Refactor the Query

I reorganized the query to do three(3) things:

create smaller temp tables
Process the WHERE clause on those temp tables
Delay joining to the very last

Here is my proposed query:

SELECT
  sounds.*,srkeys.avg_rating,srkeys.votes
FROM
(
  SELECT AA.id,avg(BB.rating) AS avg_rating, count(BB.rating) AS votes
  (
    SELECT id FROM sounds
    WHERE blacklisted = false 
    AND   ready_for_deployment = true 
    AND   deployed = true 
    AND   type = "Sound" 
    AND   created_at > '2011-03-26 21:25:49'
  ) AA INNER JOIN
  (
    SELECT AAA.ratings,AAA.rateable_id
    FROM ratings AAA
    WHERE rateable_type = 'Sound'
  ) BB
  ON AA.id = BB.rateable_id
  GROUP BY BB.rateable_id
) srkeys INNER JOIN sounds USING (id);

Recommendation #2) Index the sounds table with an index that will accommodate the WHERE clause

The columns of this index include all the columns from the WHERE clause with static values first and moving target last

ALTER TABLE sounds ADD INDEX support_index
(blacklisted,ready_for_deployment,deployed,type,created_at);

I sincerely believe you will be pleasantly surprised. Give it a Try !!!

UPDATE 2011-05-21 19:04

I just saw the cardinality. OUCH !!! Cardinality of 1 for rateable_id. Boy, I feel stupid !!!

UPDATE 2011-05-21 19:20

Maybe making the index will be enough to improve things.

UPDATE 2011-05-21 22:56

Please run this:

EXPLAIN SELECT
  sounds.*,srkeys.avg_rating,srkeys.votes
FROM
(
  SELECT AA.id,avg(BB.rating) AS avg_rating, count(BB.rating) AS votes FROM
  (
    SELECT id FROM sounds
    WHERE blacklisted = false 
    AND   ready_for_deployment = true 
    AND   deployed = true 
    AND   type = "Sound" 
    AND   created_at > '2011-03-26 21:25:49'
  ) AA INNER JOIN
  (
    SELECT AAA.ratings,AAA.rateable_id
    FROM ratings AAA
    WHERE rateable_type = 'Sound'
  ) BB
  ON AA.id = BB.rateable_id
  GROUP BY BB.rateable_id
) srkeys INNER JOIN sounds USING (id);

UPDATE 2011-05-21 23:34

I refactored it again. Try This One Please:

EXPLAIN
  SELECT AA.id,avg(BB.rating) AS avg_rating, count(BB.rating) AS votes FROM
  (
    SELECT id FROM sounds
    WHERE blacklisted = false 
    AND   ready_for_deployment = true 
    AND   deployed = true 
    AND   type = "Sound" 
    AND   created_at > '2011-03-26 21:25:49'
  ) AA INNER JOIN
  (
    SELECT AAA.ratings,AAA.rateable_id
    FROM ratings AAA
    WHERE rateable_type = 'Sound'
  ) BB
  ON AA.id = BB.rateable_id
  GROUP BY BB.rateable_id
;

UPDATE 2011-05-21 23:55

I refactored it again. Try This One Please (Last Time):

EXPLAIN
  SELECT A.id,avg(B.rating) AS avg_rating, count(B.rating) AS votes FROM
  (
    SELECT BB.* FROM
    (
      SELECT id FROM sounds
      WHERE blacklisted = false 
      AND   ready_for_deployment = true 
      AND   deployed = true 
      AND   type = "Sound" 
      AND   created_at > '2011-03-26 21:25:49'
    ) AA INNER JOIN sounds BB USING (id)
  ) A INNER JOIN
  (
    SELECT AAA.ratings,AAA.rateable_id
    FROM ratings AAA
    WHERE rateable_type = 'Sound'
  ) B
  ON A.id = B.rateable_id
  GROUP BY B.rateable_id;

UPDATE 2011-05-22 00:12

I hate giving up !!!!

EXPLAIN
  SELECT A.*,avg(B.rating) AS avg_rating, count(B.rating) AS votes FROM
  (
    SELECT BB.* FROM
    (
      SELECT id FROM sounds
      WHERE blacklisted = false 
      AND   ready_for_deployment = true 
      AND   deployed = true 
      AND   type = "Sound" 
      AND   created_at > '2011-03-26 21:25:49'
    ) AA INNER JOIN sounds BB USING (id)
  ) A,
  (
    SELECT AAA.ratings,AAA.rateable_id
    FROM ratings AAA
    WHERE rateable_type = 'Sound'
    AND AAA.rateable_id = A.id
  ) B
  GROUP BY B.rateable_id;

UPDATE 2011-05-22 07:51

It has been bothering me that ratings is coming back with 2 million rows in the EXPLAIN. Then, it hit me. You might need another index on the ratings table which starts with rateable_type:

ALTER TABLE ratings ADD INDEX
rateable_type_rateable_id_ndx (rateable_type,rateable_id);

The goal of this index is to reduce the temp table that manipulates ratings so that it is less that 2 million. If we can get that temp table significantly smaller (at least half), then we can have a better hope in your query and mine working faster too.

After making that index, please Retry my original proposed query and also try yours:

SELECT
  sounds.*,srkeys.avg_rating,srkeys.votes
FROM
(
  SELECT AA.id,avg(BB.rating) AS avg_rating, count(BB.rating) AS votes
  (
    SELECT id FROM sounds
    WHERE blacklisted = false 
    AND   ready_for_deployment = true 
    AND   deployed = true 
    AND   type = "Sound" 
    AND   created_at > '2011-03-26 21:25:49'
  ) AA INNER JOIN
  (
    SELECT AAA.ratings,AAA.rateable_id
    FROM ratings AAA
    WHERE rateable_type = 'Sound'
  ) BB
  ON AA.id = BB.rateable_id
  GROUP BY BB.rateable_id
) srkeys INNER JOIN sounds USING (id);

UPDATE 2011-05-22 18:39 : FINAL WORDS

I had refactored a query in a stored procedure and added an index to help answer a question on speeding things up. I got 6 upvotes, had the answer accepted,and picked up a 200 bounty.

I had also refactored another query (marginal results) and added an index (dramatic results). I got 2 upvotes and had the answer accepted.

I added an index for yet another query challange and was upvoted once

and now your question.

Wanting to answers all questions like these (including yours) were inspired by a YouTube video I watched on refactoring queries.

Thank you again, @coneybeare !!! I wanted to answer this question to fullest extent possible, not just accept points or accolades. Now, I can feel that I earned the points !!!

Mysql – How to improve this query

This (orders_products) is a many-to-many table. I think it's common to have 2 composite indexes on such tables as it helps in many common queries.

I would definitely add two (unique) indexes, on (orders_id, products_id) and on (products_id, orders_id).

Not sure if defining them both as UNIQUE would be a further improvement in MariaDB's optimizer.

And if there is not some special reason, you could drop the auto incremented orders_products_id column. You can identify rows in the table by the order and product ids. I think that column only adds more space in the table and indexes and no value.

Best Answer

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Mysql – How to optimize this MySQL query further

Mysql – How to improve this query

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