Let's assume we have 2 tables:
First table: "members"
id name
===========
10 Rooney
20 George
30 Hoytt
40 Percy
Second table: "interactions"
id iType mem1 mem2
===========================
5501 PRIVMSG 10 30
5502 NOTICE 20 40
And the result should be:
id iType mem1 mem2 mem1name mem2name
==========================================
5501 PRIVMSG 10 30 Rooney Hoyyt
5502 NOTICE 20 40 George Percy
How can we achive this output table using a single MySQL query?
Thanks by now.
Just use two joins and give them differen aliasses like this:
SELECT interactions.*,m1.name as 'mem1name',m2.name as 'mem2name'
FROM
interactions
LEFT JOIN members m1 ON (interactions.mem1 = m1.id)
LEFT JOIN members m2 ON (interactions.mem2 = m2.id)
Related
Here are my two tables:
[items]
- id - model - location_id -
1 mA 23
2 mA 23
3 mA 23
4 mB 24
5 mB 24
6 mC 25
7 mC 26
[locations]
- id - name -
23 aisle-3
24 aisle-4
25 aisle-5
26 aisle-6
I am trying to query the locations table for the location names and also bring back a count of the items at that location. Here is something I tried to no avail:
SELECT name, COUNT(item.id)
FROM locations
INNER JOIN items AS item ON (item.location_id = locations.id)
Can anyone help me with this?
You forgot to GROUP BY:
SELECT l.*, COUNT(item.id)
FROM locations l
INNER JOIN items AS i
ON i.location_id = l.id
GROUP BY l.id
And if you want to get COUNT() even when there is no item assigned to that location you should LEFT JOIN instead of INNER JOIN.
I've been struggling on the following.
I have 3 tables: players, players_clothes, and teams_clothes.
Table players:
id user team_id
1 tom 4
2 robo 5
3 bob 4
So tom and bob are both on the same team
Table players_clothes:
id clothes_id p_id
1 13 1
2 35 3
3 45 3
Bob has clothing article 35 and 45, robo has none.
Table teams_clothes:
id clothes_id team_id
1 35 4
2 45 4
3 55 4
4 65 5
This shows which teams have rights to which articles of clothing. The problem: tom is wearing an article of clothing that does no belong to his team... Let's assume this is illegal.
I'm having trouble figuring out how to capture all those who are wearing illegal clothes for a particular team.
SELECT pc.clothes_id FROM players AS p
JOIN players_clothes AS pc
ON p.id = pc.p_id
AND p.team_id = 4 GROUP BY pc.clothes_id
(I group by players_clothes.clothes_id because believe it or not, two players can be assigned the same piece of clothing)
I think this results the following set (13, 35, 45)
Now I would like to check against the actual set of clothes that team 4 owns.
SELECT clothes_id FROM teams_clothes WHERE team_id = 4 and this return (35, 45, 55)
How can I create a query so that it returns (13)? I've tried things like NOT EXISTS IN but I think the GROUP BY players_clothes.clothes_id part gets in the way
I suggest
select * from A where team_id = $team_id join B on B.a_id = A.id
where not exists
(
select 1 from C where C.clothes_id = B.clothes_id and team_id = $team_id
)
Basically, we find all As who are on their team and for each A join to all clothing they wear, and then only return the row IF we can't find indication in table C that the clothing is on our team (this covers not existent in C and exists but in the wrong team on C)
This should do the trick:
SELECT b.a_id, b.clothes_id
FROM
b INNER JOIN a
ON b.a_id = a.id
LEFT OUTER JOIN c
ON a.team_id = c.team_id
WHERE
c.clothes_id = NULL
The thought is to do an outer join on the combination of tables A/B against table C. And then only look for the cases where c.clothes_id is NULL, which would represent those cases where there is no relational match on the outer join (i.e. the clothes item is not approved for that user's team).
Not sure if this is too late for you, but I'd change the database model itself to make this situation impossible in the first place:
("Unimportant" fields omitted for brevity, including surrogate keys such as PLAYER_ID.)
Note how TEAM_ID migrates through the identifying relationship from TEAM to PLAYER, and then to the PLAYER_ARTICLE, where it merges with the same field migrated through the TEAM_ARTICLE. Since there is only one physical TEAM_ID field in the PLAYER_ARTICLE table, you can never insert a row that would reference different teams.
To put it in more abstract terms: this is a diamond-shaped dependency, where TEAM is at the top and PLAYER_ARTICLE at the bottom of the diamond. The merger at the bottom (enabled by the usage of identifying relationships) ensures sides must always point to the same top.
Your example data would be represented like this...
PLAYER:
TEAM_ID PLAYER_NO
4 1 -- Tom
5 1 -- Robo
4 2 -- Bob
TEAM_ATRICLE:
TEAM_ID ARTICLE_ID
4 35
4 45
4 55
5 65
PLAYER_ARTICLE:
TEAM_ID PLAYER_NO ATRICLE_ID
4 1 13 -- Tom: this is impossible (FK violation).
4 2 35 -- Bob
4 2 45 -- Bob
I need to perform a COUNT on a quite a big query, where one of the joined tables has a one-to-many relationship. This is throwing off my result as all data is being multiplied by the number of times an item is repeated in the 'many' side of the one-to-many table.
This is a shortened version of the query showing only the relevant portion to highlight the issue:
SELECT COUNT(trimtype) FROM versiontrim
INNER JOIN trims USING (trim_id)
INNER JOIN prices USING(version_id)
INNER JOIN m_versions USING(version_id)
WHERE trimtype IN('sec', 'help') AND price BETWEEN 200001 AND 210000
GROUP BY version_id
All tables are quite straighforward except m_versions that has the one-to-many relationship and looks like this:
version_id serv_id
1 1
1 2
1 3
1 4
1 5
.... and so on
The expected result of the query is :
version_id COUNT(trimtype)
44 9
54 7
69 9
214 10
216 6
282 1
290 10
Instead I am getting this,ie, all counts multiplied by 5 which is the number of times version_id is repeated in the m_versions table:
version_id COUNT(trimtype)
44 45
54 35
69 45
214 50
216 30
282 5
290 50
How to avoid this behavior?
Thanks
It matches to multiple records on table m_version that is why you are getting invalid result. Try wrapping it a subquery,
INNER JOIN (SELECT DISTINCT version_id FROM m_versions) m USING(version_id)
UPDATE
So the full query will look like this,
SELECT version_id, COUNT(trimtype)
FROM versiontrim
INNER JOIN trims USING (trim_id)
INNER JOIN prices USING(version_id)
INNER JOIN (SELECT DISTINCT version_id FROM m_versions) m USING(version_id)
WHERE trimtype IN('sec', 'help') AND price BETWEEN 200001 AND 210000
GROUP BY version_id
I have a two tables first one is called teams and second one is called cpd and I want this result required (see result screen below). I tried myself but was not successful (see practice query below).
teams table
id name sub_cat_id
1 SACRAMENTO KINGS 19
2 KINGS 19
3 MIMAMI HEAT 19
4 HEAT 20
5 KITE 20
cpd table
id team_id status added_date
1 3 1 2012-05-26
2 3 1 2012-05-27
3 3 0 2012-05-28
practice Query
SELECT
t.`id`,t.`name`,IFNULL(cpd.status,0) AS resultStatus,IFNULL(cpd.added_date,CURDATE()) AS added_date
FROM `teams` t
LEFT JOIN cpd ON cpd.team_id = t.id
WHERE t.`sub_cat_id` = 19 OR cpd.added_date = CURDATE()
Result Screen (Required only those rows are black color in screen)
Update
Explanation ?
I am trying to get those rows who they are related with sub_cat_id = 19 like this in team table
Join team table with cpd table for cpd.status filed
cpd.status must be related with current date in cpd table like 2012-05-28
There are more than one way to get the desired result:
For example:
SELECT t.`id`,t.`name`,
IFNULL(cpd.status,0) AS resultStatus,
IFNULL(cpd.added_date,CURDATE()) AS added_date
FROM `teams` t
INNER JOIN cpd ON (cpd.team_id = t.id AND cpd.status = 0)
WHERE t.`sub_cat_id` = 19
OR
cpd.added_date = CURDATE()
Your JOIN ON cpd.team_id = t.idonly matches one tuple with the cpd table so for the other tuples date is set as NULL (because you are doing LEFT JOIN) and hence the where query gives only one tuple
SELECT
t.id,t.name,IFNULL(cpd.status,0) AS resultStatus,IFNULL(cpd.added_date,CURDATE()) AS added_date
FROM teams t
LEFT JOIN cpd ON cpd.team_id = t.id
WHERE t.sub_cat_id = 19 OR cpd.added_date = CURDATE()
GROUP BY t.id
Assume I have 4 tables:
Table 1: Task
ID Task Schedule
1 Cut Grass Mon
2 Sweep Floor Fri
3 Wash Dishes Fri
Table 2: Assigned
ID TaskID (FK) PersonID (FK)
1 1 1
2 1 2
3 2 3
4 3 2
Table 3: Person
ID Name
1 Tom
2 Dick
3 Harry
Table 4: Mobile
ID PersonID (FK) CountryCode MobileNumber
1 1 1 555-555-5555
2 2 44 555-555-1234
3 3 81 555-555-5678
4 3 81 555-555-0000
I'm trying to display the
Task on a certain day
Name of person assigned to task
Phone numbers of said person
I think it should be something like the following, but I'm not sure how to set up the conditions so that the results are limited correctly:
SELECT T.ID, T.Task, P.Name, M.MobileNumber
FROM Task AS T
LEFT JOIN Assigned AS A
ON T.ID = A.TaskID
LEFT JOIN Person AS P
ON A.PersonID = P.ID
LEFT JOIN Mobile AS M
ON M.PersonID = P.ID
WHERE T.Schedule = Fri
My goal is to fetch the following information (it will be displayed differently):
Tasks Name MobileNumber
Sweep Floor, Wash Dishes Dick, Harry 44-555-555-1234, 81-555-555-5678, 81-555-555-0000
Of course, if JOIN is the wrong way to do this, please say so.
It's unclear what you want to do with duplicate data in this case, but you should be looking at using inner joins instead of outer joins, and using something like group_concat() to combine the phone numbers.