A categories table which contains id, category_name,category_type etc.
I am getting all the records with SELECT query.
suppose I have a category name Shared article and I want to get it first position in my records.
of course I am using simple query
SELECT `category_name`,`category_type`,`categories`.`id`,
count(`user_bookmarks`.`id`) as counter FROM `categories`
LEFT JOIN `user_bookmarks`
ON `categories`.`id`=`user_bookmarks`.`category_id`
WHERE `categories`.`user_id`=39 GROUP By `categories`.`category_name`
but I don't know how achieve my task?
Is it possible with MySQL?
Yes you can do as
order by
`categories`.`category_name` = 'Shared article' desc
Related
I have achieved my desired query but I want to know how this one worked. I have multiple tables on my database and my requirements was to take the id from table called product and using this id, I want to retrieve some data from multiple tables and product id is a foreign key to the other tables. The query below works fine (by the way I was just experimenting and luckily got this query).
SELECT ponsfdp.*, product.pName, product.pImage, product.productSizes FROM product
INNER JOIN priceOnSizesForDigitalPrinting AS ponsfdp ON ponsfdp.pId_fk =
(SELECT pId FROM product WHERE pName LIKE "%booklet%")
WHERE pName LIKE "%booklet%";
But when I tried this query,
SELECT ponsfdp.*, product.pName, product.pImage, product.productSizes FROM product
INNER JOIN priceOnSizesForDigitalPrinting AS ponsfdp ON ponsfdp.pId_fk =
(SELECT pId FROM product WHERE pName LIKE "%booklet%");
It contains all the data even with null fields too. Can someone explain to me how it works? My personal opinion is both query should return same data because on the second query, I am using a subquery and it returns only one id, on the other hand, first query has a WHERE clause which generates the same id but by the help of name. How does the first query returns very specific columns and second return all columns even null columns too? I need an explanation for both queries.
Your first query also returning all rows as returned from your second query. But, when you are adding the last filter-
WHERE pName LIKE "%booklet%"
It's just keeping one single row from all rows where pName is like 'booklet'. You can consider the output from your second query as a single table and your logic working as below-
SELECT * FROM (
SELECT ponsfdp.*, product.pName, product.pImage, product.productSizes
FROM product
INNER JOIN priceOnSizesForDigitalPrinting AS ponsfdp
ON ponsfdp.pId_fk = (SELECT pId FROM product WHERE pName LIKE "%booklet%")
)A
WHERE pName LIKE "%booklet%"
Hope this will at least give you some insight of your query.
I don't see any need for a subquery here. You should be using the where condition to select rows from your FROM table, then use the ON clause of your join to find the right record(s) in your joined table for each row of the FROM table:
SELECT ponsfdp.*, product.pName, product.pImage, product.productSizes
FROM product
INNER JOIN priceOnSizesForDigitalPrinting AS ponsfdp
ON ponsfdp.pId_fk = pId
WHERE pName LIKE "%booklet%";
Below are the avg_mileage table and the trucks table.
What I'm trying to do is to compile an query which allows me to select or create a table with avg_mileage.avgmpg and group by the trucks.model in order from highest to lowest of avg_mileage.avg_mpg.
Something like this:
Isn't this a simple join rather than a group by? (sorry can't "comment" because I don't have enough rep yet.)
OK, I think I get your question. You've already done.
SELECT truckid, avg(mpg) avgmpg FROM truck_mileage GROUP BY truckid;
Now you want truck.model rather than truckid, AND you want it sorted?
SELECT model, avgmpg FROM avg_mileage JOIN trucks ON (avg_mileage.truckid = trucks.truckid) ORDER BY avgmpg DESC;
Try something like that.
I only have one table to count, I am not using any join. Is this possible?
Select engagement_type as name, COUNT(engagement_type) as y
From events
group By engagement_type
order By engagement_type
But only result is 1 row with count per engagement_type. I want to show all count of accounts without any engagement_type. Like these:
Will appreciate your answers! Thanks!
If there is a lookup-table, say EngagementTypes, where all possible values of engagement types are stored, then you can query this table to get the full list of all types and do a LEFT JOIN to events table in order to get the corresponding count:
Select t1.engagement_type as name, COUNT(t2.engagement_type) as y
From EngagementTypes AS t1
left join events as t2 on t1.engagement_type = t2.engagement_type
group By t1.engagement_type
order By t1.engagement_type
I have this query:
select skill.name, IFNULL(Round(((SUM(ROUND((student_skills.value/skill.value)*100,0)))/82),0),0) as successRate from skill left JOIN student_skills on skill.id = student_skills.skill_id group by skill.name
This query returns exactly what I want but I need to replace constant 82 (just for example) with number of rows in table user (something like COUNT(user.name)).
Problem is that user is not related to skill or student_skill table in any way.
How should I alter my query so that it would use current count of users?
Thanks
Use a subquery
select skill.name,
IFNULL(Round(((SUM(ROUND((student_skills.value/skill.value)*100,0)))/(select COUNT(*) from user)),0),0) as successRate
from skill
left JOIN student_skills on skill.id = student_skills.skill_id
group by skill.name
EDIT. I missed the one main issue I was having. I want to display all the unique 'device_MAC' rows. So I want this query to output 3 rows (as per the original query). The issue I am having is connecting the data table to the remote_node table via dt_short = rn_short where the maximum timestamp for dt_short in the data table.
I am having trouble running a query on 3 tables (2 have many to many relations).
What I am trying to do:
Get each distinct rn_IEEE from the remotenodes table with the maximum timestamp (in the example this will get 3 rows with 3 distinct short addresses rn_short)
Join with the devicenames table on device_IEEE
Get each distinct dt_short from the data table with the maximum timestamp
Join dt_short with rn_short from the query above
Now the problem I am running into is that I can do the queries for the above individually, I have even gotten the first 3 of them together into a query but I cannot seem to properly join the last bit of data to get the result that I want.
I have been going in circles trying to solve this. Here is a link to SQL Fiddle which contains all the test data and the query as far as I got it, it does what i want for the first line but from table 'data' after the first line is NULL:
See this SQL fiddle
After going through your requirements and the data, it looks like you just need to change your query to include an INNER JOIN on the data table instead of a LEFT JOIN
See SQL Fiddle with Demo
select rn.*, dn.*, d.*
from remotenodes rn
inner join devicenames dn
on rn.rn_IEEE = dn.device_IEEE
and rn.rn_timestamp = (SELECT MAX(rn_timestamp) FROM remotenodes
WHERE rn.rn_IEEE = rn_IEEE
GROUP BY rn_IEEE)
inner join data d
on rn.rn_short = d.dt_short
AND d.dt_timestamp = (SELECT MAX(d2.dt_timestamp) AS ts
FROM data d2
WHERE d.dt_short = d2.dt_short
GROUP BY d2.dt_short)
what you have done the query in your SQL fiddle is right.Instead of using left join use inner join so that it will give you the first row
cheers.
Thanks for all your answers everyone. I managed to solve the problem by using views.
It's not the most efficient way but I think it will do for now.
Here is the SQL Fiddle link:
http://sqlfiddle.com/#!2/4076e/8
Try this query, for me its returning one row:
SELECT rn_short, rn_IEEE, device_name
FROM
(SELECT DISTINCTROW dt_short FROM (SELECT * FROM `data` ORDER BY `dt_timestamp` DESC) as data ) as a
JOIN
(SELECT rn_IEEE, rn_short, device_name FROM devicenames dn JOIN (SELECT DISTINCTROW rn_IEEE, rn_short FROM (SELECT * FROM `remotenodes` ORDER BY `rn_timestamp` DESC) as remotenodes GROUP BY rn_IEEE) as rn ON dn.device_IEEE = rn.rn_IEEE) as b
ON a.dt_short = b.rn_short