i have 3 tables like this
questions_table
question_id | content | user |
1 | my first question | userOne#email.com |
2 | my second question | userTwo#email.com|
replies_table
reply_id | question_id|user |content |voteCount|
1 | 1 |userSeven#email.com |first reply question 1 |0 |
2 | 1 |userEight#email.com |second reply question1 |0 |
vote_table
vote_id | reply_id| voted_by |
1 | 2 | userThree#email.com|
2 | 2 | userFour#email.com |
so to explain this:
A question was posted by two users userOne#email.com and
UserTwo#email.com
Then userSeven#email.com and userEight#email.com replied to
question 1.
Then the reply of userEight#email.com which has a reply_id of 2 was voted up by
userThree#email.com and userFour#email.com
what i need to do is to write an event scheduler in myphpmyadmin which will run every 2 hours.
what i want the query to do is to update the column voteCount in replies_table by counting the votes on that reply id.
this is what i got so far
SELECT COUNT(voteCount)
FROM replies_table
WHERE reply_id = .../**dont know how am i suppose to do this part **/;
i know it would be something like this but i have never wrote a event scheduler
You may simply use join to get the total vote count.
select r.reply_id, v.Countreply as count from replies_table as r
inner join
(select reply_id, count(reply_id) as CountReply from vote_table group by reply_id) as v
on r.reply_id= v.reply_id
If you want to update then it is simply done by update.
update r set r.votecount = v.Countreply
from replies_table as r inner join
(select reply_id, count(reply_id) as CountReply from vote_table group by reply_id) as v
on r.reply_id= v.reply_id
In MySQL, you would express the update as:
i want the query to do is to update the column voteCount in replies_table by counting the votes on that reply id. this is what i got so far
update replies_table rt join
(select reply_id, count(*) as numvotes
from votes v
group by reply_id
) v
set rt.VoteCount = v.numvotes;
This may not be the best way to keep your data up-to-date.
If your tables are not very big, then there is no need to store the VoteCount separately. Just run the query when you need it.
If the VoteCount is actually important, then use a trigger to keep it up-to-date.
And, there is no need to update all the rows, even if you take this route. You can keep track of timestamps and the last time updated to limit the number of updates.
Related
my client was given the following code and he uses it daily to count the messages sent to businesses on his website. I have looked at the MYSQL.SLOW.LOG and it has the following stats for this query, which indicates to me it needs optimising.
Count: 183 Time=44.12s (8073s) Lock=0.00s (0s)
Rows_sent=17337923391683297280.0 (-1), Rows_examined=382885.7
(70068089), Rows_affected=0.0 (0), thewedd1[thewedd1]#localhost
The query is:
SELECT
businesses.name AS BusinessName,
messages.created AS DateSent,
messages.guest_sender AS EnquirersEmail,
strip_tags(messages.message) AS Message,
users.name AS BusinessName
FROM
messages
JOIN users ON messages.from_to = users.id
JOIN businesses ON users.business_id = businesses.id
My SQL is not very good but would a LEFT JOIN rather than a JOIN help to reduce the number or rows returned? Ive have run an EXPLAIN query and it seems to make no difference between the LEFT JOIN and the JOIN..
Basically I think it would be good to reduce the number of rows returned, as it is absurdly big..
Short answer: There is nothing "wrong" with your query, other than the duplicate BusinessName alias.
Long answer: You can add indexes to the foreign / primary keys to speed up searching which will do more than changing the query.
If you're using SSMS (SQL management studio) you can right click on indexes for a table and use the wizard.
Just don't be tempted to index all the columns as that may slow down any inserts you do in future, stick to the ids and _ids unless you know what you're doing.
he uses it daily to count the messages sent to businesses
If this is done per day, why not limit this to messages sent in specific recent days?
As an example: To count messages sent per business per day, for just a few recent days (example: 3 or 4 days), try this:
SELECT businesses.name AS BusinessName
, messages.created AS DateSent
, COUNT(*) AS n
FROM messages
JOIN users ON messages.from_to = users.id
JOIN businesses ON users.business_id = businesses.id
WHERE messages.created BETWEEN current_date - INTERVAL '3' DAY AND current_date
GROUP BY businesses.id
, DateSent
ORDER BY DateSent DESC
, n DESC
, businesses.id
;
Note: businesses.name is functionally dependent on businesses.id (in the GROUP BY terms), which is the primary key of businesses.
Example result:
+--------------+------------+---+
| BusinessName | DateSent | n |
+--------------+------------+---+
| business1 | 2021-09-05 | 3 |
| business2 | 2021-09-05 | 1 |
| business2 | 2021-09-04 | 1 |
| business2 | 2021-09-03 | 1 |
| business3 | 2021-09-02 | 5 |
| business1 | 2021-09-02 | 1 |
| business2 | 2021-09-02 | 1 |
+--------------+------------+---+
7 rows in set
This assumes your basic join logic is correct, which might not be true.
Other data could be returned as aggregated results, if necessary, and the fact that this is now limited to just recent data, the amount of rows examined should be much more reasonable.
I have two tables looking like this
Patient (table 1)
id | name
------------
1 | robel
2 | dave
Patient_followup (table 2)
id | Patient_id | date_created
-----------------------
1 | ---- 1 -- | 01/01/2015
2 | -----1 -- | 01/07/2016
I want to display all the patients with their perspective latest followup data. so i tried using this query
Select * from patient
left join Patient_followup pf on pf.Patient_id = patient.id
order by pf.date_created
Limit 1
but this is giving me only the first patient robel. i tryed removing the limit and its giving me two records of robel and one record of dave because robel has two followup data. so what should i do to get only one record of each patient ?
Try this:
Select
*
from
patient
left join
(SELECT
id as pf_id,
MAX(date_created) as latest_followup_date,
Patient_id
FROM
Patient_followup
GROUP BY
Patient_id) as pf
ON pf.Patient_id = patient.id
As mentioned by anton in the first comment, you need to use aggregation to get one record per patient.
Select patient.*,MAX(pf.date_created) as followupdate,group_concat(pf.date_created) from patient
left join Patient_followup pf on pf.Patient_id = p.patient.id
group by patient.id
order by pf.date_created
Here, you will get your values comma separated.
1) "Limit 1" will only return the first result. Typically this is used if the query will result in a very large result set and you only want the first few results.
Ex:
"LIMIT 30" will show the first 30 rows of the query.
2) I would change to setup of the tables so the query is smoother. Right now, you create a new line for each follow-up date even if the patient is already created. You could add another column in the table named "FollowUpDate". That way each patient record has the table id, patient id, creation date and followup date in the same row. That way, each patient has only one row.
EX:
Patient (table 1)
id | name | created_date | next_followup_date |
1 | Robel | 01/01/2015 | 01/01/2016 |
2 | Dave |[created_date]| [next_follup_date] |
Patient_followup (table 2)
id | Patient_id | date_created | followUpDate |
1 | 1 | 01/01/2015 | 06/01/2016 | // example date
2 | 1 | 01/01/2015 | 01/01/2016 |
3 | 2 |[date created]| [FollowUpDate] |
3) Change query to:
Use this select statement to get all patient records.
Select * from patient
left join Patient_followup pf on pf.Patient_id = patient.id
order by pf.Patient_id
Use this select statement to get the specific patient record information.
Select * from patient
inner join Patient_followup pf on pf.Patient_id = patient.id
where patient.id = 1 //to get robel. Edit this line as necessary, perhaps by user input...
order by pf.followUpDate
NOTE: When you insert a new record in Patient_followup, make sure you update Patient.next_followup_date.
I hope this helps!
Not sure if this is possible but I have a schema like this:
id | user_id | thread_id
1 | 1 | 1
2 | 4 | 1
3 | 1 | 2
4 | 3 | 2
I am trying to retrieve the thread_id where user_id = 1 and 4. I know that in(1,4) does not fit my needs as its pretty much a OR and will pull up record 3 as well and Exists only returns a bool.
You may use JOIN (that answer already exists) or HAVING, like this:
SELECT
thread_id,
COUNT(1) AS user_count
FROM
t
WHERE
user_id IN (1,4)
GROUP BY
thread_id
HAVING
user_count=2
-check the demo. HAVING will fit better in case of many id's (because with JOIN you'll need to join as many times as many id you have). This is a bit tricky, however: you may do = comparison only if your records are unique per (user_id, thread_id); for example, your user_id can repeat, then use >=, like in this demo.
Try this with join, i guess you need to do AND operation with user_id must be 4 and 1 then
SELECT
t1.thread_id
FROM
TABLE t1
JOIN TABLE t2
ON (t1.user_id = t2.user_id)
WHERE t1.user_id = 1
AND t2.user_id = 4
I read many topics about this problem but I can't find the solution.
I have a table (called users) with the users of my website. They have points. For example:
+-----------+------------+
| User_id | Points |
+-----------+------------+
| 1 | 12258 |
| 2 | 112 |
| 3 | 9678 |
| 4 | 689206 |
| 5 | 1868 |
+-----------+------------+
On the top of the page the variable $user_id is set. For example the user_id is 4. Now I would like to get the rank of the user by points (output should be 1 if the user_id is 4).
Thank you very much!
SELECT
COUNT(*) AS rank
FROM users
WHERE Points>=(SELECT Points FROM users WHERE User_id=4)
Updated with some more useful stuff:
SELECT
user_id,
points,
(SELECT COUNT(*)+1 FROM users WHERE Points>x.points) AS rank_upper,
(SELECT COUNT(*) FROM users WHERE Points>=x.points) AS rank_lower
FROM
`users` x
WHERE x.user_id = 4
which includes the range of ranks user is at. So for example if the scores for first five places are 5 4 3 3 3, the result would be:
id points rank_upper rank_lower
id 5 1 1
id 4 2 2
id 3 3 5
id 3 3 5
id 3 3 5
This query should do what you want :
SELECT rank FROM (
SELECT User_id, Points,
FIND_IN_SET(
Points,
(SELECT GROUP_CONCAT(
DISTINCT Points
ORDER BY Points DESC
)
FROM users)
) as rank
FROM users )
WHERE User_id = 4;
If you don't want to do it outside mysql you'll need to use variables to compute the rank.
Here's a solution that describes exactly what you want :
http://www.fromdual.ch/ranking-mysql-results
You still need, it you want to have it directly for each record, to store it in the record and to update it yourself. There is no reasonable query that will give you directly the rank without storage on a real table (I mean not just a few hundreds records).
There's already a simple solution, just suited for your purpose.
This may help
SELECT #rank:=#rank+1 AS rank,`User_id`,`Points` FROM `users` u JOIN (SELECT #rank:=0) r ORDER BY u.Points DESC
For simplicity, I will give a quick example of what i am trying to achieve:
Table 1 - Members
ID | Name
--------------------
1 | John
2 | Mike
3 | Sam
Table 1 - Member_Selections
ID | planID
--------------------
1 | 1
1 | 2
1 | 1
2 | 2
2 | 3
3 | 2
3 | 1
Table 3 - Selection_Details
planID | Cost
--------------------
1 | 5
2 | 10
3 | 12
When i run my query, I want to return the sum of the all member selections grouped by member. The issue I face however (e.g. table 2 data) is that some members may have duplicate information within the system by mistake. While we do our best to filter this data up front, sometimes it slips through the cracks so when I make the necessary calls to the system to pull information, I also want to filter this data.
the results SHOULD show:
Results Table
ID | Name | Total_Cost
-----------------------------
1 | John | 15
2 | Mike | 22
3 | Sam | 15
but instead have John as $20 because he has plan ID #1 inserted twice by mistake.
My query is currently:
SELECT
sq.ID, sq.name, SUM(sq.premium) AS total_cost
FROM
(
SELECT
m.id, m.name, g.premium
FROM members m
INNER JOIN member_selections s USING(ID)
INNER JOIN selection_details g USING(planid)
) sq group by sq.agent
Adding DISTINCT s.planID filters the results incorrectly as it will only show a single PlanID 1 sold (even though members 1 and 3 bought it).
Any help is appreciated.
EDIT
There is also another table I forgot to mention which is the agent table (the agent who sold the plans to members).
the final group by statement groups ALL items sold by the agent ID (which turns the final results into a single row).
Perhaps the simplest solution is to put a unique composite key on the member_selections table:
alter table member_selections add unique key ms_key (ID, planID);
which would prevent any records from being added where the unique combo of ID/planID already exist elsewhere in the table. That'd allow only a single (1,1)
comment followup:
just saw your comment about the 'alter ignore...'. That's work fine, but you'd still be left with the bad duplicates in the table. I'd suggest doing the unique key, then manually cleaning up the table. The query I put in the comments should find all the duplicates for you, which you can then weed out by hand. once the table's clean, there'll be no need for the duplicate-handling version of the query.
Use UNIQUE keys to prevent accidental duplicate entries. This will eliminate the problem at the source, instead of when it starts to show symptoms. It also makes later queries easier, because you can count on having a consistent database.
What about:
SELECT
sq.ID, sq.name, SUM(sq.premium) AS total_cost
FROM
(
SELECT
m.id, m.name, g.premium
FROM members m
INNER JOIN
(select distinct ID, PlanID from member_selections) s
USING(ID)
INNER JOIN selection_details g USING(planid)
) sq group by sq.agent
By the way, is there a reason you don't have a primary key on member_selections that will prevent these duplicates from happening in the first place?
You can add a group by clause into the inner query, which groups by all three columns, basically returning only unique rows. (I also changed 'premium' to 'cost' to match your example tables, and dropped the agent part)
SELECT
sq.ID,
sq.name,
SUM(sq.Cost) AS total_cost
FROM
(
SELECT
m.id,
m.name,
g.Cost
FROM
members m
INNER JOIN member_selections s USING(ID)
INNER JOIN selection_details g USING(planid)
GROUP BY
m.ID,
m.NAME,
g.Cost
) sq
group by
sq.ID,
sq.NAME