The query below takes ~2 seconds, which seems really long for such a straightforward join on 2 tables with only ~3000 or so rows.
I strongly suspect the problem is with this line:
but I'm not sure why. Or, perhaps the join condition is screwing things up?
SELECT DISTINCT
, idnum
, DATEDIFF( DATE_ADD(atable.adate, INTERVAL 10 DAY), btable.bdate) as `DIFF`
FROM atable
LEFT JOIN btable
ON atable.idnum = btable.idnum
;
My issue is similar to this, but not the same. Thanks in advance to the great SO community for looking this over.
You can reduce time by creating view of this query and call that view rather than direct query to table.like this
Create view
CREATE VIEW viewname AS SELECT DISTINCT
, idnum
, DATEDIFF( DATE_ADD(atable.adate, INTERVAL 10 DAY), btable.bdate) as `DIFF`
FROM atable
LEFT JOIN btable
ON atable.idnum = btable.idnum
;
Call view
SELECT * FROM viewname
Note: in view approach we create view at once and call that view as many times as we want.
Related
I've ran into some performance issues with my database structure "or better to say my query instead "
I have a the following table :
http://sqlfiddle.com/#!9/348cb
And following query trying to fetch certain data, and after that trying to check if there are other records matching my conditions, it's all in the following query.
it is working as expected, the only reason that I'm asking this question is that if there is a way I could increase its performance or use another way to get the results.
As you can see, There two ( SELECT )'s which trying to check if there are any other records containing current query data.
SELECT (
SELECT COUNT(*) FROM log AS LIKES
WHERE L.target_account=LIKES.target_account
AND LIKES.type='like'
) as liked,
(
SELECT COUNT(*) FROM log AS COMMENTS
WHERE L.target_account=COMMENTS.target_account
AND COMMENTS.type='follow_back'
) as follow_back,
(
SELECT COUNT(*) FROM log AS FOLLOW_BACK
WHERE L.target_account=FOLLOW_BACK.target_account
AND COMMENTS.type='follow_back'
) as follow_back,
L.*
FROM `log` as L
WHERE `L`.`information` = '".$target_name."'
AND `L`.`account_id` = '".$id."'
AND `L`.`date_ts` BETWEEN CURDATE() - INTERVAL ".$limit." DAY AND CURDATE()
This query takes too much time to fetch the data.
Thanks in advance.
You may be able to rewrite the query, depending on the relationship between target account and account id.
In the meantime, you want indexes. The two you want are instagram_log(target_account, type) and instagram_log(account_id, information, date_ts):
create index idx_instagram_log_1 on instagram_log(target_account, type);
create index idx_instagram_log_2 on instagram_log(account_id, information, date_ts);
SELECT SUM(LIKES) LIKES,SUM(FOLLOW_BACK) FOLLOW_BACK,SUM(COMMENTS) FROM
(
SELECT
CASE WHEN L.type='like' THEN 1 ELSE 0 END LIKES,
CASE WHEN L.type='follow_back' THEN 1 ELSE 0 END FOLLOW_BACK,
CASE WHEN L.type='comments' THEN 1 ELSE 0 END COMMENTS
FROM `log` as L
WHERE `L`.`information` = '".$target_name."'
AND `L`.`account_id` = '".$id."'
AND `L`.`date_ts` BETWEEN CURDATE() - INTERVAL ".$limit." DAY AND CURDATE()
)Z
Try the above query.
When I run the stored procedure for the first time, it is so slow and the process lasts for 1 minute, and then I run it again and it lasts 10 seconds.
Following is my main sql statement, please help me to check out , thank you very much！
example 1
SELECT sql_no_cache view_address.is_facility,count(DISTINCT
view_address.provider_id)as totalCount FROM pv_mview_provider_address view_address WHERE
view_address.network_group_id=5047 AND view_address.carrier_group_id=93 GROUP BY
view_address.is_facility;
explain:
example 2：
SELECT SQL_NO_CACHE is_facility,count(distinct provider_id) FROM (SELECT
view_address.provider_id,view_address.is_facility FROM pv_mview_provider_address
view_address WHERE view_address.network_group_id=5047 AND view_address.carrier_group_id=93
) as p GROUP BY is_facility
explain:
this sql will spend 10 s to load the data.
The table stores 4000,0000 rows.
Thank you very much！
For this query:
select sql_no_cache a.is_facility,
count(distinct a.provider_id) as totalCount
from pv_mview_provider_address a
where a.network_group_id = 5047 and
a.carrier_group_id = 93
group by a.is_facility;
You want an index. The best index is pv_mview_provider_address(network_group_id, carrier_group_id, is_facility). However, if the reference in the from clause is a view and not a table, then you need to figure out what is happening with the view.
I'm not an expert in SQL, i have an sql statement :
SELECT * FROM articles WHERE article_id IN
(SELECT distinct(content_id) FROM contents_by_cats WHERE cat_id='$cat')
AND permission='true' AND date <= '$now_date_time' ORDER BY date DESC;
Table contents_by_cats has 11000 rows.
Table articles has 2700 rows.
Variables $now_date_time and $cat are php variables.
This query takes about 10 seconds to return the values (i think because it has nested SELECT statements) , and 10 seconds is a big amount of time.
How can i achieve this in another way ? (Views or JOIN) ?
I think JOIN will help me here but i don't know how to use it properly for the SQL statement that i mentioned.
Thanks in advance.
A JOIN is exactly what you are looking for. Try something like this:
SELECT DISTINCT articles.*
FROM articles
JOIN contents_by_cats ON articles.article_id = contents_by_cats.content_id
WHERE contents_by_cats.cat_id='$cat'
AND articles.permission='true'
AND articles.date <= '$now_date_time'
ORDER BY date DESC;
If your query is still not as fast as you would like then check that you have an index on articles.article_id and contents_by_cats.content_id and contents_by_cats.cat_id. Depending on the data you may want an index on articles.date as well.
Do note that if the $cat and $now_date_time values are coming from a user then you should really be preparing and binding the query rather than just dumping these values into the query.
This is the query we are starting with:
SELECT a.*
FROM articles a
WHERE article_id IN (SELECT distinct(content_id)
FROM contents_by_cats
WHERE cat_id ='$cat'
) AND
permission ='true' AND
date <= '$now_date_time'
ORDER BY date DESC;
Two things will help this query. The first is to rewrite it using exists rather than in and to simplify the subquery:
SELECT a.*
FROM articles a
WHERE EXISTS (SELECT 1
FROM contents_by_cats cbc
WHERE cbc.content_id = a.article_id and cat_id = '$cat'
) AND
permission ='true' AND
date <= '$now_date_time'
ORDER BY date DESC;
Second, you want indexes on both articles and contents_by_cats:
create index idx_articles_3 on articles(permission, date, article_id);
create index idx_contents_by_cats_2 on contents_by_cat(content_id, cat_id);
By the way, instead of $now_date_time, you can just use the now() function in MySQL.
I didn't expect to find this so difficult, but I'm trying to set a user variable in MySQL to contain an array of values. I have no clue how to do this so tried doing some research and was quite suprised to find no answer. I have tried:
SET #billable_types = ['client1','client2','client3'];
The reason being I would like to use the variable in the following statement later on:
SELECT sum((time_to_sec(timediff(tlg.time_stop, tlg.time_start))/3600)) as billable_hours
from mod_tmlog_time_log tlg, mod_tmlog_task_list mttl
where date(tlg.time_start) >= #time_start
and date(tlg.time_stop) <= #time_stop
and mttl.type IN (#billable_types)
and tlg.task_id = mttl.id
group by start_date
order by start_date desc;
Would be very grateful for help.
Fast forward a while, I ended up with the following quick and dirty solution which doesn't give me the flexibility of re-using the array elsewhere in the code but hey it's an unchargeable admin task so I don't want to spend any more time on it.
SELECT WEEKDAY(tlg.time_start) AS day_of_week, date(tlg.time_start) as start_date,
sum((time_to_sec(timediff(tlg.time_stop, tlg.time_start))/3600)) as billable_hours
from mod_tmlog_time_log tlg, mod_tmlog_task_list mttl
where date(tlg.time_start) >= #time_start
and date(tlg.time_stop) <= #time_stop
and mttl.type IN ('c1','c2','c3')
and tlg.task_id = mttl.id
group by start_date
order by start_date desc;
joostschouten seems to have found the most elegant solution (not tested it myself yet) but next time I'm writing something which calls for this I will remember to test it!
Just found the answer here: How to cycle with an array in MySQL?
set #billable_types = 'client1,client2,client3';
select * from mttl where find_in_set(mttl.type, #billable_types);
As Marc B mentioned, there is no array variable in MYSQL.
The alternative to find_in_set solution is to use SELECT with UNION to simulate the array:
SELECT billable_type FROM (
SELECT 'client1' AS billable_type UNION
SELECT 'client2' AS billable_type UNION
SELECT 'client3' AS billable_type) AS t
So your query will looks like that:
SELECT sum((time_to_sec(timediff(tlg.time_stop, tlg.time_start))/3600)) as billable_hours
from mod_tmlog_time_log tlg, mod_tmlog_task_list mttl
where date(tlg.time_start) >= #time_start
and date(tlg.time_stop) <= #time_stop
and mttl.type IN (
SELECT billable_type FROM (
SELECT 'client1' AS billable_type UNION
SELECT 'client2' AS billable_type UNION
SELECT 'client3' AS billable_type) AS t
)
and tlg.task_id = mttl.id
group by start_date
order by start_date desc;
If the user has the CREATE TABLE privilege, an array can be simulated by creating a temporary, single-column table. A value or values in the table can be retrieved with a SELECT statement. Temporary tables are dropped at the end of the session, but it's a good idea to explicitly drop them once they're no longer needed.
CREATE TEMPORARY TABLE billable_types (c VARCHAR(16));
INSERT INTO billable_types VALUES ('client1'), ('client2'), ('client3');
SELECT sum((time_to_sec(timediff(tlg.time_stop, tlg.time_start))/3600)) as billable_hours
from mod_tmlog_time_log tlg, mod_tmlog_task_list mttl
where date(tlg.time_start) >= #time_start
and date(tlg.time_stop) <= #time_stop
and mttl.type IN (SELECT * FROM billable_types)
and tlg.task_id = mttl.id
group by start_date
order by start_date desc;
DROP TABLE billable_types;
i have this query
SELECT
IF(isnull(ub.user_lecture_id), 0, ub.user_lecture_id) as IsPurchased,
cs.title,cs.start_date, cs.start_time, cs.end_time
FROM campus_schedule cs
LEFT JOIN campus_bookinfo cb ON cs.bookid=cb.idx_campus_bookinfo
LEFT JOIN user_lectures ub ON ub.id_product = cs.idx_campus_schedule AND ub.id_customer = 11
WHERE cs.idx_campus = 1 and cs.title like '%%' and cs.status=1
Which Shows:
Click to view Output
Explanation: if (IsPurchased == 0) it is not yet bought my customer
My Question: if you look at the time of row with IsPurchased=1, the time range is conflicting with the time in IsPurchases=0. how can i compare and conclude that the time of the same date of the query is conflicting to the time and date of the other rows. results may be 1 or 0 in a "conflict" field name
Hope you got the point. Thanks for the help!!!
To compare times, you will find it easier to use DATETIME fields.
To check for "conflicting" rows, you'll probably need to have a subquery in the WHERE clause.
Subquery should work but will be inefficient in mysql. You should create temporary table and analyze it. Or do the same inline, like:
set #lastdate=0;
set #lasttime=0;
select IsPurchased, title, start_date, start_time, end_time, if(#lastdate = start_date, #lasttime < end_time, 1) as CONFLICT, #lastdate:=start_date, #lasttime:=start_time
from (your_query ORDER BY start_date, start_time, end_time) t ;
that is just an idea, it worked for me several times.