I have table like:
user :
uid | course_id | subjects
---------------------------
1 | 1 | html,php
2 | 1 | java,html,sql
3 | 1 | java
4 | 1 | fashion,html,php,sql,java
I want to run a query which can return most liked subjects in query and then second most and so on...
For Example :
select * from user where subjects like '%java%' or '%php%' or '%html%';
this query will return data like this:
uid | course_id | subjects
---------------------------
2 | 1 | java,html,sql
3 | 1 | java
4 | 1 | fashion,html,php,sql,java
but i want output like this :
uid | course_id | subjects
---------------------------
4 | 1 | fashion,html,php,sql,java
2 | 1 | java,html,sql
1 | 1 | html,php
3 | 1 | java
so the most matched subjects 1st then 2nd most matched subjects and so on....
Is there any modification in my query so that i can get this type of sorted output.
Never, never, never store multiple values in one column!
Like you see now this will only give you headaches. Normalize your user table. Then you can select normally.
It should look like this
uid | course_id | subjects
---------------------------
1 | 1 | html
1 | 1 | php
2 | 1 | java
2 | 1 | html
2 | 1 | sql
3 | 1 | java
...
or better introduce an new table subjects and then make a mapping table called course_subjects
subject
id | name
------------
1 | html
2 | sql
3 | java
...
course_subjects
uid | course_id | subject_id
---------------------------
1 | 1 | 1
1 | 1 | 2
...
Based on the way you want your results, it looks like you want to order by the number of subjects (or tags) within subject. This can be accomplished by counting the number of , (commas).
The way to count the number of occurances of a character is to subtract the original length by the length when the character is removed.
Example:
SELECT *
FROM USER
WHERE subjects LIKE '%java%'
OR '%php%'
OR '%html%'
ORDER BY ( Length(subjects) - Length(Replace(subjects, ',', '')) ) DESC;
SQLFiddle: http://sqlfiddle.com/#!2/cc793/4
Result:
UID COURSE_ID SUBJECTS
4 1 fashion,html,php,sql,java
2 1 java,html,sql
3 1 java
Note:
As juergen says it is a bad idea to store multiple values in one column.
With MyISAM storage engine you can do match against.
The simplest example:
SELECT *,
MATCH (subjects) AGAINST ('java php html') AS relevance
FROM `user`
WHERE MATCH (subjects) AGAINST ('java php html')
ORDER BY relevance DESC
In MySQL 5.6 full-text search is available with InnoDB too but needs a bit extra to make it work. For more info checkout the following post: http://www.mysqlperformanceblog.com/2013/03/04/innodb-full-text-search-in-mysql-5-6-part-2-the-queries/
Related
I have two tables in a MySQL database like this:
User:
userid |userid | Username | Plan(VARCHAR) | Status |
-----------+------------+--------------+---------------+---------+
1 | 1 | John | 1,2,3 |1 |
2 | 2 | Cynthia | 1,2 |1 |
3 | 3 | Charles | 2,3,4 |1 |
Plan: (planid is primary key)
planid(INT) | Plan_Name | Cost | status |
-------------+----------------+----------+--------------+
1 | Tamil Pack | 100 | ACTIVE |
2 | English Pack | 100 | ACTIVE |
3 | SportsPack | 100 | ACTIVE |
4 | KidsPack | 100 | ACTIVE |
OUTPUT
id |userid | Username | Plan | Planname |
---+-------+----------+------------+-------------------------------------+
1 | 1 | John | 1,2,3 |Tamil Pack,English Pack,SportsPack |
2 | 2 | Cynthia | 1,2 |Tamil Pack,English Pack |
3 | 3 | Charles | 2,3,4 |English Pack,Sportspack, Kidspack |
Since plan id in Plan table is integer and the user can hold many plans, its stored as comma separated as varchar, so when i try with IN condition its not working.
SELECT * FROM plan WHERE find_in_set(plan_id,(select user.planid from user where user.userid=1))
This get me the 3 rows from plan table but i want the desired output as above.
How to do that.? any help Please
A rewrite off your query what should work is as follows..
Query
SELECT
all columns you need
, GROUP_CONCAT(Plan.Plan_Name ORDER BY Plan.planid) AS Planname
FROM
Plan
WHERE
FIND_IN_SET(Plan.plan_id,(
SELECT
User.Plan
FROM
user
WHERE User.userid = 1
)
)
GROUP BY
all columns what are in the select (NOT the GROUP_CONCAT function)
You also can use FIND_IN_SET on the ON clause off a INNER JOIN.
One problem is that the join won't ever use indexes.
Query
SELECT
all columns you need
, GROUP_CONCAT(Plan.Plan_Name ORDER BY Plan.planid) AS Planname
FROM
User
INNER JOIN
Plan
ON
FIND_IN_SET(Plan.id, User.Plan)
WHERE
User.id = 1
GROUP BY
all columns what are in the select (NOT the GROUP_CONCAT function)
Like i said in the comments you should normalize the table structures and add the table User_Plan whats holds the relations between the table User and Plan.
I am trying to write a mySQL statement that selects data from one table but counts up entries from another table with a matching ID in a specific field.
The two tables are jobs and job_cards. A job will always be a single entry which will have multiple job cards, so I need to write a singular statement that selects data from the job table but adds another field in the result which is a count of all related job cards.
Example:
jobs table:
| ID | customer | status | date_added |
|----------------------------------------|
| 1 | 3 | active | 2017-10-10 |
------------------------------------------
job_cards table is a bit more complex but includes a column called job_id which will be 1 in this case. But lets say there are 3 cards assigned to the job above. I wrote the following statement:
SELECT j.*, COUNT(jc.id) AS card_count FROM jobs j LEFT JOIN job_cards jc ON j.id = jc.job_id
But the count column only returns the TOTAL number of cards in the job_cards table, regardless of which job they are assigned to. Not only that, but it only ever returns a single result even though at the moment there are 4 entries in the jobs table.
Is there any way to do what I need to do with a single statement?
EDIT:
Sample data from the job_cards table:
| ID | job_id | customer | description | materials | notes |
|--------------------------------------------------------------|
| 1 | 1 | 3 | blah blah | none | test |
| 2 | 1 | 3 | something | pipes | n/a |
----------------------------------------------------------------
The result I would like to get is:
| ID | customer | date_added | card_count |
|-------------------------------------------|
| 1 | 3 | 2017-10-10 | 2 |
---------------------------------------------
Where the ID here is the ID of the job.
You can try this:
SELECT *, (select count(*)
from job_cards jc
where jc.job_id=j.id) as card_count
FROM jobs j
Given a structure like this in a MySQL database
#data_table
(id) | user_id | time | (...)
#relations_table
(id) | user_id | user_coach_id | (...)
we can select all data_table rows belonging to a certain user_coach_id (let's say 1) with
SELECT rel.`user_coach_id`, dat.*
FROM `relations_table` rel
LEFT JOIN `data_table` dat ON rel.`uid` = dat.`uid`
WHERE rel.`user_coach_id` = 1
ORDER BY val.`time` DESC
returning something like
| user_coach_id | id | user_id | time | data1 | data2 | ...
| 1 | 9 | 4 | 15 | foo | bar | ...
| 1 | 7 | 3 | 12 | oof | rab | ...
| 1 | 6 | 4 | 11 | ofo | abr | ...
| 1 | 4 | 4 | 5 | foo | bra | ...
(And so on. Of course time are not integers in reality but to keep it simple.)
But now I would like to query (ideally) only up to an arbitrary number of rows from data_table per distinct user_id but still have those ordered (i.e. newest first). Is that even possible?
I know I can use GROUP BY user_id to only return 1 row per user, but then the ordering doesn't work and it seems kind of unpredictable which row will be in the result. I guess it's doable with a subquery, but I haven't figured it out yet.
To limit the number of rows in each GROUP is complicated. It is probably best done with an #variable to count, plus an outer query to throw out the rows beyond the limit.
My blog on Groupwise Max gives some hints of how to do such.
I need a list of user IDs (course_user_ids) that is currently stored in a single field of a larger table.
I have a table called courses that contains course information with course_id and course_students as such:
-----------------------------------------------------------
| course_id | course_students |
----------------------------------------------------------
| 1 | a:3:{i:0;i:12345;i:1;i:22345;i:2;i:323456;} |
-----------------------------------------------------------
| 2 | a:32:{ … } |
-----------------------------------------------------------
The course_students part contains 3 chunks of information:
the number of students (a:3:{…) -- not needed
the order/key for the array of each student ({i:0;… i:1;… i:2; …}) -- also not needed
the course_user_id (i:12345; … i:22345;… i:32345;)
I only need the course_user_id and the original course_id, resulting in a new table that i can use for joins/subqueries like this:
------------------------------
| course_id | course_user_id |
------------------------------
| 1 | 12345 |
------------------------------
| 1 | 22345 |
------------------------------
| 1 | 323456 |
------------------------------
(ideally able to continue to break out values for other course_ids and course_user_ids, but not a priority:)
| … | … |
------------------------------
| 2 | … |
------------------------------
| 2 | … |
------------------------------
| 97 | … |
------------------------------
| 97 | … |
------------------------------
| … | … |
------------------------------
Note: the course_user_id can vary in length (some are 5 digits, some are 6)
Any ideas would be much appreciated!
Update
My user table does have user_id which can be mapped to course_students or course_user_id, so that is a very helpful observation from below.
I also think I need to use a LEFT JOIN because some students are registered in multiple courses, and I'd like to see each instance/combo.
Let us assume that you have a table name users which contains all users data along with user_id.
Now you can join table courses and table users in following manner:
select c.course_id,u.user_id
from
courses c
join users u
on u.user_id=if(instr(c.course_students,concat(":",u.user_id,";"))>0,u.user_id,c.course_students)
You get the result as per your requirement.
Verify at http://sqlfiddle.com/#!9/3667d/2
Note: The above query works fine if no overlapping between user_id and array index. In case of overlapping, kindly filter data using where-clause
If I got your goal correctly you have users table. And {i:0;i:12345;i:1;i:22345;i:2;i:323456; equal users.id=12345,users.id=22345 etc.
If my guess is correct you can try this solution:
http://sqlfiddle.com/#!9/cfef27/5
SELECT * FROM courses
LEFT JOIN users u
ON courses.course_students LIKE CONCAT('%i:',u.id,';%')
I have a question about my DB table structure. I want to know if i'm on the right track or if I have missed a good alternative. Here is the case:
To make it easy to read, I haven't pasted the full contents as my question is only about the structure.
2 tables:
1: id (AI), task
2: id, name, task
Table 1 presents dynamic check-boxes which can be altered by an admin panel so the contents would be like this
1 task1
2 task2
5 task5
(3 & 4 are missing cause the administrator deleted those records).
In table number two are the people who should do the tasks from table 1. And the goal is that the tasks wich are not checked will be displayed.
So the contents of table 2 would be:
1 Name1 1,5
2 Name2 1,2
3 Name3 1,2,5
The numbers in table 2 represent the checked boxes from table 1. So with a query i can compare the numbers from table 2 with the id's from table 1 and display the missing ids as "todo".
In my opinion this looks very overdone, and there must be an easier way to create dynamic options which can be compared and stored as a todo.
Suggestions are welcome!
I suggest you to use basic structure for many-to-many relationship:
tasks users user_tasks
+----+-----------+ +----+-------+ +---------+---------+
| id | name | | id | name | | user_id | task_id |
+----+-----------+ +----+-------+ +---------+---------+
| 1 | Buy milk | | 1 | John | | 1 | 2 |
| 2 | Get drunk | | 2 | Tim | | 3 | 2 |
| 3 | Have fun | | 3 | Steve | | 2 | 4 |
| 4 | Go home | +----+-------+ | 3 | 4 |
+----+-----------+ +---------+---------+
And you can fetch unassigned tasks using following query:
SELECT
tasks.*
FROM
tasks
LEFT JOIN
user_tasks
ON (tasks.id = user_tasks.task_id)
WHERE
user_tasks.user_id IS NULL
You also can fetch users who have no assigned tasks:
SELECT
users.*
FROM
users
LEFT JOIN
user_tasks
ON (users.id = user_tasks.user_id)
WHERE
user_tasks.user_id IS NULL
Hope this will help you.