I have persons (table person) who have 0 or N roles (tables role and personne_role).
I want to select all the persons , with the roles they have, to have this kind of result :
PHIL COLLINS | Drummer | Singer
MIKE RUTHERFORD | Singer
ION ANDERSON | Singer
MIKE JAGGER |
CARLOS SANTANA | Guitarist
......
Each line can have 0 or N roles.
To do that, I make 2 requests
the first one to get the employees (table person)
the second one to loop all the retrieved employees and retrieve each role of them (tables role and person_role)
It works BUT in the case of there are a lot of lines, it is not very efficient.
I would like the same result in 1 request.
Is it possible ?
What are the mysql keywords I must use to do that ?
Thanks for your feedback.
dominique
You could use a JOIN with a GROUP_CONCAT, something like:
SELECT person.name, role.roles
FROM person
LEFT JOIN (
SELECT person_id, GROUP_CONCAT(DISTINCT role SEPARATOR ' | ') roles
FROM person_role
GROUP BY person_id
) role ON (person.id = role.person_id)
EDIT: the fields name are just a guess, since you didn't show us the full table schema; also, if the roles are actually in a separate tale, say joined by a role_id, you'd need to add it to the subquery.
Related
I'm having this problem which I'm unsure how to resolve.
Here's the situation : I want to get a list of all individuals who have not completed a survey. It is however possible for someone to start/complete multiple surveys.
Therefore, I want the list of individuals who have not completed at least one survey.
Here's what my query looks likes to get the list of people with incomplete surveys :
SELECT Survey.UserID, Survey.Fullname
FROM [...]
WHERE Survey.SurveySubmitted = 0 -- 0 = Unsubmitted, 1 = submitted
Now this is what the database could look like
UserID Fullname SurveySubmitted
1 John Smith 0
2 Jane Doe 1
3 Tom Glass 0
3 Tom Glass 1
Now the above query will select both John Smith and Tom Glass. However, since Tom Glass already completed at least one survey, he should be excluded.
Any ideas to proceed? It most likely needs a SELECT within another SELECT but I'm having trouble picturing it.
You could check for the user not in the user that have submited/completed
select Survey.UserID, Survey.Fullname
from [.....]
where UserID NOT IN (
SELECT Survey.UserID, Survey.Fullname
FROM [...]
WHERE Survey.SurveySubmitted = 1
)
You should group by whatever uniquely identifies a User/Survey combination and then sum the # of surveys that have been submitted. You can then use a having clause to filter out rows > 0:
select *
from Survey
group by UserId, FullName
having sum(SurveySubmitted) = 0;
SQLFiddle Example
I have two databases, one holds family names and the other holds family members.
Since separate family names (lastnames) can be shared between people not related, they are assigned a family "ID" which is shared across both databases.
familyNames : lastName | ID
memberNames : firstName | ID
I want to count how many members each family has, the output looking like:
Family Name | Members
----------------------
Johnson | 14
----------------------
Brown | 21
----------------------
White | 33
Is there a way to do this without creating a new column? Thanks.
(The familyNames holds many more columns that are irrelevant to the problem, hence the reason to have two tables)
select f.lastname, count(m.firstname) as cnt
from familynames f
left join membernames m on m.id = f.id
group by f.id, f.lastname
order by f.lastname
HERE Database names are prefixed to table names , DB1, DB2 are database names.
SELECT FN.lastName as 'Family Name', COUNT(*) as Members FROM
DB1.familyNames FN
JOIN DB2.memberNames MN
on FN.ID = MN.ID
group by FN.lastName
Alright I am guessing I need a subquery to solve this and I am little rusty on these. So I have 3 tables:
tblAccount - Has User information and AccountID
tblItem - Has Item information and ItemID
tblAccountItem - Has 3 fields - AccountItemID / AccountID / ItemID
An account can have many items and an item can have many accounts. Example data:
tblAccount
AccountID AccountName AccountEmail
1 John Smith john#smith.com
2 Fred John fred#john.com
3 George Mike george#mike.com
tblItem
ItemID ItemName ItemDescription
1 Hammer Smashes things
2 Axe Breaks things
Ok so lets say the Hammer belongs to John,Fred and George. Axe only belongs to John and Fred.
tblAccountItem
AccountItemID AccountID ItemID
1 1 1
2 2 1
3 3 1
4 1 2
5 2 2
So I want to show what items John has and also show who else owns that item. The output I want to show is:
ItemName ItemDescription OtherOwners
Hammer Smashes things Fred, George
Axe Breaks things Fred
Any help would be greatly appreciated!
The answer by ctrahey is perfect but I have a slight condition to add. There are 2 types of accounts in tblAccount denoted by a field.
tblAccount
AccountID AccountName AccountEmail AccountDescription AccountTypeID
1 John Smith john#smith.com NULL 1
2 Fred John fred#john.com NULL 1
3 George Mike george#mike.com Runner 2
tblAccountTypeID
AccountTypeID AccountType
1 User
2 Admin
If the AccountTypeID is 1 then I need to output the AccountEmail. If the AccountTypeID is 2 I need to output the AccountDescription. Eg output (same story as above):
ItemName ItemDescription OtherOwners
Hammer Smashes things Fred, Runner
Axe Breaks things Fred
Going off the query that ctrahey I am guessing there needs to be an ALIAS field created. Something like:
WHERE AccountTypeID = 1 (SELECT AccountName)
WHERE AccountTypeID = 2 (SELECT AccountDescription)
I hope this makes sense, thanks for all the help so far!
Subqueries are very rarely actually needed, and are often replaced (with improved performance) by a well-designed JOIN.
Here, we start with AccountItem table (the WHERE clause immediately limits the query to only items owned by our account of interest); then we join the same table (aliasing it to 'others_items_join'), telling it to join with the same itemID but not owned by our account if interest. That's the essence of the entire query, the next two joins are only to bring in the actual strings we want to be in our output (the other people's names and the item names/descriptions). GROUP BY is used to give just one row per item which our account of interest has.
SELECT
ItemName,
ItemDescription,
GROUP_CONCAT(others.AccountName) as OtherOwners
FROM
tblAccountItem as my_items
LEFT JOIN tblAccountItem as others_items_join
ON others_items_join.ItemID = my_items.ItemID AND others_items_join.AccountID != ?
LEFT JOIN tblAccount as others
ON others_items_join.AccountID = others.AccountID
JOIN tblItems ON my_items.ItemID = tblItems.ItemID
WHERE my_items.AccountID = ?
GROUP BY ItemName
You better use a coding to resole this , here rough query that's may helps you get an idea :
SELECT AccountName
FROM tblAccount
WHERE AccountID = (SELECT AccoundID
FROM tblAccountItem
WHERE itemID = (SELECT itemID
FROM tblAccountItem
WHERE AccountID = 1 (john Id as example)));
Hope this helps
SELECT ItemName, ItemDescription, AccountItemID FROM tblitem RIGHT JOIN tblaccountitem ON tblitem.ItemID=tblaccountitem.ItemID
I hope this helps lead to your answer. I am still looking into this
Using phpMyAdmin 5.1.44 to experiment with DML commands.
I've been following tutorials on-line.
SELECT book.b_isbn, publisher.p_name FROM 'book', 'publisher' WHERE book.b_title='DSA'
Table 1
book
b_id(PK) b_isbn b_title p_id(FK)
-----------------------------------------
1 12345 DSA 1
2 23456 SD 1
3 34567 CSP 2
Table 2
publisher
p_id(PK) p_name
--------------------
1 Fred
2 John
Expected Results
b_isbn p_name
---------------------
12345 Fred
Actual Results
b_isbn p_name
----------------------
12345 Fred
34567 John
Any ideas?
You need to tell MySQL how to join the tables together (without which it just matches every book to every publisher) - use any one of:
add AND publisher.p_id = book.p_id to your WHERE clause;
tell MySQL to join ON that condition / USING that column;
... FROM book JOIN publisher ON publisher.p_id = book.p_id WHERE ...
or
... FROM book JOIN publisher USING (p_id) WHERE ...
use a NATURAL JOIN to have MySQL guess that's what you want based on the column names.
... FROM book NATURAL JOIN publisher WHERE ...
I think you need to put the fk to the pk key in the where statement
SELECT
*
FROM
book, publisher
WHERE
book.p_id=publisher.p_id
AND book.b_title='DSA'
Or even better use JOINs:
SELECT
*
FROM
book
JOIN publisher
ON book.p_id=publisher.p_id
WHERE
book.b_title='DSA'
Or if you are not sure if there is a corresponding value then use a left join. Like this:
SELECT
*
FROM
book
LEFT JOIN publisher
ON book.p_id=publisher.p_id
WHERE
book.b_title='DSA'
I have two tables.
Table Emp
id name
1 Ajay
2 Amol
3 Sanjay
4 Vijay
Table Sports
Sport_name Played by
Cricket ^2^,^3^,^4^
Football ^1^,^3^
Vollyball ^4^,^1^
Now I want to write a query which will give me output like
name No_of_sports_played
Ajay 2
Amol 1
Sanjay 2
Vijay 2
So what will be Mysql query for this?
I agree with the above answers/comments that you are not using a database for what a database is for, but here is how you could calculate your table from your current structure in case you have no control over that:
SELECT Emp.name, IF(Played_by IS NULL,0,COUNT(*)) as Num_Sports
FROM Emp
LEFT JOIN Sports
ON Sports.Played_by RLIKE CONCAT('[[:<:]]',Emp.id,'[[:>:]]')
GROUP BY Emp.name;
See it in action here.
UPDATE: added the IF(Played_by IS NULL,0,COUNT(*)) instead of COUNT(*). This means that if an employee doesn't play anything they'll have a 0 as their Num_Sports. See it here (I also added in those ^ characters and it still works.
What it does is joins the Emp table to the Sports table if it can find the Emp.id in the corresponding Played_by column.
For example, if we wanted to see what sports Ajay played (id=1), we could do:
SELECT *
FROM Emp, Sports
WHERE Sports.Played_by LIKE '%1%'
AND Emp.id=1;
The query I gave as my solution is basically the query above, with a GROUP BY Emp.name to perform it for each employee.
The one modification is the use of RLIKE instead of LIKE.
I use RLIKE '[[:<:]]employeeid[[:>:]]' instead of LIKE '%employeeid%. The [[:<:]] symbols just mean "make sure the employeeid you match is a whole word".
This prevents (e.g.) Emp.id 1 matching the 1 in the Played_by of 3,4,11,2.
You do not want to store your relationships in a column like that. Create this table:
CREATE TABLE player_sports (player_id INTEGER NOT NULL, sport_id INTEGER NOT NULL, PRIMARY KEY(player_id, sport_id));
This assumes you have an id column in your sports table. So now a player will have one record in player_sports for each sport they play.
Your final query will be:
SELECT p.name, COUNT(ps.player_id)
FROM players p, player_sports ps
WHERE ps.player_id = p.id
GROUP BY p.name;