I have a situation where I have to use EAV table design.
I have the following two tables.
Nodes
id name structure_id
1 name 1 7
2 name 2 7
Attributes
id node_id name value structure_id
1 1 firstname test 7
2 1 lastname test 7
3 2 firstname test 7
I have the following query
SELECT n.*, GROUP_CONCAT( CONCAT_WS('||', a.name, a.value) ORDER BY a.name SEPARATOR ';;' ) as _attributes
FROM nodes n JOIN attributes a ON n.structure_id = a.structure_id where n.structure_id = 7
The above query outputs the following (only ONE row)
id: 1
name: name 1
structure_id: 7
_attributes: firstname||test;;firstname||test;;firstname||test;;firstname||test;;lastname||test;;lastname||test
How do I make it to output two rows from nodes table with their rows from attributes?
You will obtain desired result set if join nodes and attributes tables by structure_id and node_id.
Desired result set: "from nodes table with their rows from attributes" .
http://sqlfiddle.com/#!2/83643/1
Good luck
select n.id,n.name,n.structure_id,firstname,lastname from Nodes n
join (select node_id, a.value as firstname from Attributes a where a.name='firstname' ) matches1 on matches1.node_id = n.id
left join (select node_id, a.value as lastname from Attributes a where a.name='lastname' ) matches2 on matches2.node_id = n.id
Related
I have a database with the following tables: Students, Classes, link_student_class. Where Students contains the information about the registered students and classes contains the information about the classes. As every student can attend multiple classes and every class can be attended by multiple students, I added a linking-table, for the mapping between students and classes.
Linking-Table
id | student_id | class_id
1 1 1
2 1 2
3 2 1
4 3 3
In this table both student_id as well as class_id will appear multiple times!
What I am looking for, is a SQL-Query that returns the information about all students (like in 'SELECT * FROM students') that are not attending a certain class (given by its id).
I tried the following SQL-query
SELECT * FROM `students`
LEFT JOIN(
SELECT * FROM link_student_class
WHERE class_id = $class_id
)
link_student_class ON link_student_class.student_id = students.student_id
Where $class_id is the id of the class which students i want to exclude.
In the returned object the students i want to include and those i want to exclude are different in the value of the column 'class_id'.
Those to be included have the value 'NULL' whereas those I want to exclude have a numerical value.
NOT EXISTS comes to mind:
select s.*
from students s
where not exists (select 1
from link_student_class lsc
where lsc.student_id = s.student_id and
lsc.class_id = ?
);
The ? is a placeholder for the parameter that provides the class.
you should check for NULL link_student_class.student_id
SELECT *
FROM `students`
LEFT JOIN(
SELECT *
FROM link_student_class
WHERE class_id = $class_id
) link_student_class ON link_student_class.student_id = students.student_id
where link_student_class.student_id is null
Or also a NOT IN predicate:
WITH
stud_class(id,stud_id,class_id) AS (
SELECT 1, 1,1
UNION ALL SELECT 2, 1,2
UNION ALL SELECT 3, 2,1
UNION ALL SELECT 4, 3,3
)
,
stud(stud_id,fname,lname) AS (
SELECT 1,'Arthur','Dent'
UNION ALL SELECT 2,'Ford','Prefect'
UNION ALL SELECT 3,'Tricia','McMillan'
UNION ALL SELECT 4,'Zaphod','Beeblebrox'
)
SELECT
s.*
FROM stud s
WHERE stud_id NOT IN (
SELECT
stud_id
FROM stud_class
WHERE class_id= 2
);
-- out stud_id | fname | lname
-- out ---------+--------+------------
-- out 3 | Tricia | McMillan
-- out 4 | Zaphod | Beeblebrox
-- out 2 | Ford | Prefect
-- out (3 rows)
-- out
-- out Time: First fetch (3 rows): 9.516 ms. All rows formatted: 9.550 ms
table 1 - employee
id empname
--------------
1 andy
2 brady
table 2 - employee phone numbers
id number empid
----------------
1 1111 1
2 2222 2
3 3333 1
4 4444 1
Need a sql query to display the following
id empname numbers
------------------
1 andy 1111,3333,4444
2 brady 2222
If you are using MySQL, you can use GROUP_CONCAT funcion, that basically concatenate every value composing the group. You could try this:
SELECT EMP.ID,
EMP.EMPNAME,
GROUP_CONCAT(EPH.NUMBER) AS NUMBERS
FROM EMPLOYEE EMP
JOIN EMPLOYEE_PHONE EPH
ON EMP.ID = EPH.EMPID
GROUP BY EMP.ID
Also, if you want to separate your values with something different of a "," you can add the syntax SEPARATOR " " after the column inside group concat, if you want to separate with spaces in this particular example
if you use SQL SERVER I think this will do it for you, if not maybe a close guess without data. But! I used STUFF and selected the Number and split them by , and ordered it
SELECT
t1.ID,t2v1.empname,
STUFF((SELECT ',' + t2v2.number
FROM Table2 t2v2
WHERE t2v2.ID = t2v1.ID
ORDER BY number
FOR XML PATH('')), 1, 1, '') [numbers]
FROM Table1 t1
inner join table2 t2v1 on t1.id = t2v1.id
GROUP BY t1.ID, t1.Name
ORDER BY 1
Try this:
SELECT e.id, e.name, CONCATENATE(ep.number, ',') as phonelist
FROM Employees e INNER JOIN EmployeePhone ep ON e.id = ep.empid
Reference Doc: http://www.peteonsoftware.com/index.php/2009/12/11/creating-a-comma-separated-list-from-a-sql-grouping/
I have a Table that tracks followers
FollowerUserId, FollowingUserId
1 2
2 1
3 1
4 1
1 5
I want to get all user that given Id follows and is followed by or Both.
for example for UserId 1,I want result to be: (FG: Following, FD: Followed, B: Both ways)
2,B
5,FG
3,FD
4,FD
i can easily get FG and FD by doing union
Select FollowerUserId, 'FD' From Table Where FollowingUserId =1
Union
Select FollowingUserId, 'FG' From Table Where FollowerUserId =1;
with above i get user 2 as
2,FG
2,FD
from above but I really need 2,B without UserId 2 duplicated.
How can this be done efficiently?
You can use aggregation on your basic query:
SELECT UserId,
(CASE WHEN COUNT(DISTINCT which) = 1 THEN MIN(which)
ELSE 'B'
END)
FROM (Select FollowerUserId as UserId, 'FD' as which From Table Where FollowingUserId = 1
Union ALL
Select FollowingUserId, 'FG' From Table Where FollowerUserId = 1
) f
GROUP BY UserId;
UPDATED
id | id_list
1 | 2,3,5,7
2 | 1,4,5,6
3 | 1,4,6,7
4 | 2,3,5,8
5 | 1,2,4,8
6 | 2,3,7,8
7 | 1,3,6,9
8 | 4,5,6,9
9 | 7,8
let's say I'm up to the content of id=1
I wanted to select all the rows where id is in id_list of id=1 PLUS the row where id=1
so the result would be
rows with id = 1,2,3,5,7
How to do this query guys?
You can also use a self join
Using IN()
select * from atable a
join atable b on (a.id = b.id )
where 1 IN (a.id_list) or b.id =1
Fiddle with IN()
Using FIND_IN_SET()
select * from atable a
join atable b on (a.id = b.id )
where FIND_IN_SET('1', a.id_list) or b.id =1
Fiddle with FIND_IN_SET()
Using UNION ALL
select * from atable
where id =1
UNION ALL
select * from atable
where 1 IN (id_list)
Fiddle with UNION ALL
Your database design is broken; id_list should be represented as a join table instead of as a string. However, to solve your immediate problem:
select * from table where id=1
or id_list like '1%'
or id_list like '%,1,%'
or id_list like '%,1'
Adjust as needed for PreparedStatement. You have to provide all three cases because if you just did
or id_list like '%1%'
and id_list contained the value 11, you'd get an incorrect match
Try this (see SQL-Fiddle):
SELECT * FROM tbl
WHERE id = 1
OR INSTR((SELECT id_list FROM tbl WHERE id = '1'), id) > 0;
Tested with MySQL 5.5.30
try this one
select *
from tbl
where id=1
or id_list like '%1%'
This appears to call for a union of two sets. The one set would be the single row whose id matches the specified value:
SELECT
id
FROM
atable
WHERE
id = #id
The other set would be the result of this self-join:
SELECT
item.id
FROM
atable AS item
INNER JOIN
atable AS list
ON
FIND_IN_SET(item.id, list.id_list)
WHERE
list.id = #id
That is, the row with the specified id is matched against every row in the table on the condition that the other row's id is found in the specified row's id_list.
You can try the complete query at SQL Fiddle.
Please note that lists aren't a very good design feature. In your situation, it might be better to use a many-to-many table as suggested by #Othman. Only I would probably use a slightly different query to get the desired output, because his doesn't include the specified row itself:
SELECT
id
FROM
manytomany
WHERE
id = #id
UNION
SELECT
linked_id
FROM
manytomany
WHERE
id = #id
;
While the entries in manytomany are assumed to be unique, the query uses the UNION DISTINCT operator because of the potential duplicates returned by the first subquery, although it is possible to move the application of DISTINCT to the first subquery only like this:
SELECT DISTINCT
id
FROM
manytomany
WHERE
id = #id
UNION ALL
SELECT
linked_id
FROM
manytomany
WHERE
id = #id
;
That first subquery could actually be rewritten simply as SELECT #id AS id, but the rewrite would only make sense if the passed value was guaranteed to be valid, i.e. that it would definitely be found in manytomany.id.
Here's a demo for the other approach too (all three variations, including the SELECT #id AS id one).
I don't have an answer for your question but I encourage you to redesign your table like this I think this called many to many relation
id | friend
1 | 2
1 | 3
1 | 5
1 | 7
2 | 1
2 | 4
2 | 5
2 | 6
3 | 1
3 | 4
3 | 6
3 | 7
And then your query will be like this
SELECT DISTINCT(friend) FROM `new` WHERE id = 1
I am assuming you are using php..
My suggestion is to grab the id_list for id 1.
Explode that id_list on the comma, and then do another mysql query to grab the remaining results for 5|3|6|8
ex) $idarray = explode(",", $result);
select * from your_table where id in ('5','3','6','8')
OPTION 2:
SELECT * FROM your_table
WHERE id = '1'
OR id IN ('\''+(SELECT REPLACE(id_list,',','\',\'') FROM your_table WHERE id = '1')+'\'')
EDIT: Oops, sorry, that should be an OR instead.
I'm trying to find the leagues (lid) where two users are apart of.
Here are my tables:
Table leagues:
*id* lname
--------------
1 Hard C
3 Fun
5 Crazy
Table match:
*userid* *lid*
-----------------
1 1
4 5
1 3
2 1
4 1
4 3
*Are primary keys
match.lid is foreign key to leagues.id (a user cannot not be part of the same league twice)
Here's what I have so far (a start):
SELECT t1.lid, t2.lname
FROM match t1
JOIN leagues t2 on t1.lid = t2.id
So far I managed to join the two tables and get the names. My ultimate goal is to show the lid's where two users are part of the same league, say userid 1 and 4.
userid 1 is a member of lid 1 and 3
userid 4 is a member of lid 5, 1, and 3
Both users meet in league(lid) 1 and 3
So I need a query that shows only the league where both users meet. Like this:
lid lname
--------------
1 Hard C
3 Fun
Since userid 1 and 4 meet in league 1 and 3, the results should show that. I can run two queries for each user and check which leagues both users meet via php, but I think it's more efficient to run one query.
SELECT m1.lid, l.lname FROM
`match` m1, `match` m2, leagues l
WHERE m1.lid = m2.lid AND m1.lid = l.id
AND m1.userid = 1
AND m2.userid = 4
There are a few ways. The most straightforward is:
SELECT id AS lid,
lname
FROM leagues
WHERE id IN
( SELECT lid
FROM match
WHERE userid = 1
)
AND id IN
( SELECT lid
FROM match
WHERE userid = 4
)
;
Another way, which is a bit less direct, but may perform better — you can try it and see — is to use JOIN:
SELECT id AS lid,
lname
FROM leagues
JOIN match AS match1
ON match1.lid = leagues.id
AND match1.userid = 1
JOIN match AS match2
ON match2.lid = leagues.id
AND match2.userid = 4
;