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
Related
i am trying to fine tune a query which runs on application dashboard.
Query is like i have a master table & few transaction tables. I have to make some calculation on transataion table & showcase same output along with few columns from the master table.
I tried with join that worked but query is not fast enough for application ( 40Sec for 1k Records).
I am trying with sub query but maybe i am making mistake somewhere.
sharing dummy details below.
Master table :
id
name
1
Cell1
2
Cell2
3
Cell3
4
Cell4
transaction table 1 Session1
| id | TotalMarks |
| 1 | 21 |
| 1 | 21 |
| 2 | 23 |
| 3 | 24 |
Transaction table 2 Session2
| id | TotalMarks |
| 1 | 22 |
| 2 | 28 |
| 4 | 25 |
| 4 | 29 |
Result i want Like
| id | Name | ObtainMarksSession1 | totalObtainMarkSession2 |
| 1 | cell1 |
| |
I have checked indexes already but anyway index won't help as i am using aggregate function.
join query
Select m.id,m.name,sum(s1.TotalMarks) ObtainMarksSession1, sum(s1.TotalMarks) ObtainMarksSession2
from master join session1 s1 on m.id=s1.id and s1.id is not null
join session2 s2 on m.id=s2.id and s2.id is not null
group by m.id,m.name;
subquery Sample
Select id, sum(TotalMarks) ObtainMarksSession1 from session1 where id is not null;
Same way i got result from other table also but now i am unable to merge both output. these single query output are very fast.
Need to know how to merge result & get output with name as well from master. also, other suggestion if i can try some other method to make this query fast.
P.s Id is not primary key in transaction table so there might be possiblity for null values.
I have a question and don't know how to approach the problem exactly.
I have two tables as following:
Clients
| c_id | name | reference |
| ---- | ------- | --------- |
| 1 | ClientA | 1 |
| 2 | ClientB | 1 |
| 3 | ClientC | 2 |
| 4 | ClientD | 2 |
| 5 | ClientE | 1 |
| 1 | ClientF | 3 |
Tour
| t_id | name | count |
| ---- | ------- | ----- |
| 1 | TourA | 3 |
| 2 | TourB | 2 |
| 3 | TourC | 1 |
"Reference" in the "Client" table is defined as foreign key.
Is it possible to fill the column "count" in the table "Tour" with an automated formula where it counts how many times the t_id appears in the "Client" table?
Something like: COUNT(c_id) FROM clients WHERE reference = t_id
I have read about to create a view but not sure how to fetch the data correctly.
Thanks for your help,
Raphael
UPDATE #1:
The workflow as described with the view works perfectly. I'm trying now to fill the column via a trigger but I'm getting an SQL error with the following code:
CREATE TRIGGER client_count
AFTER UPDATE
ON clients FOR EACH ROW
SELECT t.*,
(
SELECT COUNT(*) FROM clients c where c.tour_id = t.tour_id
) AS tours.tour_bookedspace
FROM tours t
The view you have referred to is indeed the way to go here. The view you need to create needs to join the two tables and perform a count aggregation as follows:
CREATE VIEW vwTour
AS
SELECT t.t_id,
t.name,
COUNT(t.name) AS Cnt
FROM tour t
JOIN Clients c
ON t.t_id = c.reference
GROUP BY t_id,
t.name
No you can't. Generated columns can only use data from the same table.
The options you have are:
1. Use a view
You can select from a view that computes the extra value(s) you want. For example:
create view tour_data as
select t.*,
(
select count(*) from clients c where c.reference = t.t_id
) as number_of_clients
from your t
2. Use a trigger
Alternatively, you can add the extra column number_of_clients and populate it using a trigger every time a row is added, modified, or deleted from the table clients.
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 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 two tables
one as td_job which has these structure
|---------|-----------|---------------|----------------|
| job_id | job_title | job_skill | job_desc |
|------------------------------------------------------|
| 1 | Job 1 | 1,2 | |
|------------------------------------------------------|
| 2 | Job 2 | 1,3 | |
|------------------------------------------------------|
The other Table is td_skill which is this one
|---------|-----------|--------------|
|skill_id |skill_title| skill_slug |
|---------------------|--------------|
| 1 | PHP | 1-PHP |
|---------------------|--------------|
| 2 | JQuery | 2-JQuery |
|---------------------|--------------|
now the job_skill in td_job is actualy the list of skill_id from td_skill
that means the job_id 1 has two skills associated with it, skill_id 1 and skill_id 2
Now I am writing a query which is this one
SELECT * FROM td_job,td_skill
WHERE td_skill.skill_id IN (SELECT td_job.job_skill FROM td_job)
AND td_skill.skill_slug LIKE '%$job_param%'
Now when the $job_param is PHP it returns one row, but if $job_param is JQuery it returns empty row.
I want to know where is the error.
The error is that you are storing a list of id's in a column rather than in an association/junction table. You should have another table, JobSkills with one row per job/skill combination.
The second and third problems are that you don't seem to understand how joins work nor how in with a subquery works. In any case, the query that you seem to want is more like:
SELECT *
FROM td_job j join
td_skill s
on find_in_set(s.skill_id, j.job_skill) > 0 and
s.skill_slug LIKE '%$job_param%';
Very bad database design. You should fix that if you can.