I have a couple of tables. One table with Groups:
[ID] - [ParentGroupID]
1 - NULL
2 1
3 1
4 2
And another with settings
[Setting] - [GroupId] - [Value]
Title 1 Hello
Title 2 World
Now I'd like to get "Hello" back if I'd query the Title for Group 3
And I'd like to get "World" back if I'd query the Title for Group 4 (And not "Hello" as well)
Is there any way to efficiently do this in MSSQL? At the moment I am resolving this recursively in code. But I was hoping that SQL could solve this problem for me.
Don't knoww the SQL Server syntax but something like the following?
SELECT settings.value
FROM settings
JOIN groups ON settings.groupid = groups.parentgroupid
WHERE settings.setting = 'Title'
AND groups.id = 3
This is a problem we've encountered multiple times in our company. This would work for any case, including when the settings can be set only at some levels and not others (see SQL Fiddle http://sqlfiddle.com/#!3/16af0/1/0 :
With GroupSettings(group_id, parent_group_id, value, current_level)
As
(
Select g.id as group_id, g.parent_id, s.value, 0 As current_Level
From Groups As g
Join Settings As s On s.group_id = g.id
Where g.parent_id Is Null
Union All
Select g.id, g.parent_id, Coalesce((Select value From Settings s Where s.group_id=g.id), gs.value), current_level+1
From GroupSettings as gs
Join Groups As g On g.parent_id = gs.group_id
)
Select *
From GroupSettings
Where group_id=4
I believe the following is what you are seeking. See the sqlfiddle
SELECT vALUE FROM
Groups g inner join Settings s
ON g.ParentGroupId = s.GroupID
WHERE g.ID = 3 -- will return Hello,], set ID = 4 will return World
Related
Hello I would like to retrieve the name and the first name in the user table thanks to the id contained in the message table (id_receive and id_send) in sql via a subquery
SELECT user.nom FROM user
WHERE user.id IN (
SELECT message.id_send, message.id_receive FROM message WHERE message.id=1
)
```
I would recommend using EXISTS, twice:
SELECT u.nom
FROM user u
WHERE EXISTS (SELECT 1 FROM message m WHERE m.id = 1 AND u.id = id_send) OR
EXISTS (SELECT 1 FROM message m WHERE m.id = 1 AND u.id = id_receive) ;
However, a JOIN might also be appropriate:
SELECT u.nom
FROM user u JOIN
message m
ON u.id IN (m.id_send, id_receive)
WHERE m.id = 1;
I suspect it isn't actually what you want but it looks like this is what you're trying to do:
SELECT user.nom FROM user
WHERE user.id IN (
SELECT message.id_send FROM message WHERE message.id=1
UNION ALL
SELECT message.id_receive FROM message WHERE message.id=1
)
The query that drives the IN should return a single column of values
Try and conceive that in works like this:
SELECT * FROM t WHERE c IN(
1
2
3
)
Not like this:
SELECT * FROM t WHERE c IN(
1 2 3
)
Nor like this:
SELECT * FROM t WHERE c IN(
1 2 3
4 5 6
)
It might help you reember that the query inside it must return a single column, but multiple rows, all of qhich are searched for a matching value c by IN
Small addition to your original query to make it working:
SELECT user.nom FROM user
WHERE user.id IN (
SELECT unnest(array[message.id_send, message.id_receive])
FROM message
WHERE message.id=1
)
Table 1 looks like the following.
ID SIZE TYPE SERIAL
1 4 W-meter1 123456
2 5 W-meter2 123456
3 4 W-meter 585858
4 4 W-Meter 398574
As you can see. Items 1 and 2 both have the same Serial Number. I have an innerjoin update statement that will update the UniqueID on these devices based on linking their serial number to the list.
What I would like to do. Is modify by hand the items with duplicate serial numbers and scripted update the ones that are unique. Im presuming I have to reference the distinct command here somewhere buy not sure.
This is my update statement as is. Pretty simple and straight forward.
update UM00400
Set um00400.umEquipmentID = tb2.MIUNo
from UM00400 tb1
inner join AA_Meters tb2 on
tb1.umSerialNumber = tb2.Old_Serial_Num
where tb1.umSerialNumber <> tb2.New_Serial_Num
;WITH CTE
AS
(
SELECT * , rn = ROW_NUMBER() OVER (PARTITION BY SERIAL ORDER BY SERIAL)
FROM UM00400
)
UPDATE CTE
SET CTE.umEquipmentID = tb2.MIUNo
inner join AA_Meters tb2
on CTE.umSerialNumber = tb2.Old_Serial_Num
where tb1.umSerialNumber <> tb2.New_Serial_Num
AND CTE.rn = 1
This will update the 1st record of multiple records with the same SERIAL.
If i understand your question correctly below query will help you out :
;WITH CTE AS
(
// getting those serial numbers which are not duplicated
SELECT umSerialNumber,COUNT(umSerialNumber) as CountOfSerialNumber
FROM UM00400
GROUP BY umSerialNumber
HAVING COUNT(umSerialNumber) = 1
)
UPDATE A SET A.umEquipmentID = C.MIUNo
FROM UM00400 A
INNER JOIN CTE B ON A.umSerialNumber = B.umSerialNumber
INNER JOIN AA_Meters C ON A.umSerialNumber = C.Old_Serial_Num
I'm trying to make an sql request with join exclusion.
Explains:
Table element
id # name #
1 Sea
2 tree
Table colour
id # name #
1 green
2 blue
3 brown
Table relation
element_id # colour_id
1 2
2 1
2 3
I have my working request for "get elements for one of these colours".
Exemple with green and blue:
SELECT element.name, colour.name FROM element
LEFT JOIN relation
ON (element.id = relation.element_id)
LEFT JOIN colour
ON (colour.id = relation.colour_id)
WHERE (relation.colour_id = 1 OR relation.colour_id = 2)
I would like make request for "get elements where they have a relation with all listed colors". Where for green and brown it returns tree.
I've tried to change the 'OR' to 'AND' but request return 0 results :/
General way to solve this problem is to filter values and count how many times they appear in result. If equal, all elements are found.
select element_id
from relation
where colour_id in (1, 2)
group by element_id
having count (distinct colour_id) = 2
Having this table one might join it to original tables to produce full column set:
SELECT element.name, colour.name
FROM relation
INNER JOIN
(
select element_id
from relation
where colour_id in (1, 2)
group by element_id
having count (distinct colour_id) = 2
) matches
ON relation.element_id = matches.element_id
INNER JOIN element
ON element.id = relation.element_id
INNER JOIN colour
ON colour.id = relation.colour_id
This type of query can be handled with some of SQL's set-based operators:
Which elements have relations for all colours?
Using the ALL operator (syntax may vary slightly by database):
SELECT element.name
FROM element
WHERE ( SELECT colour.id FROM relation
INNER JOIN colour ON colour.id = relation.colour_id
WHERE relation.element_id = element.id )
= ALL ( SELECT colour.id from colour)
;
Using the EXCEPT operator:
SELECT element.name
FROM element
WHERE NOT EXISTS
( SELECT colour.id from colour
EXCEPT
SELECT colour.id FROM relation
INNER JOIN colour ON colour.id = relation.colour_id
WHERE relation.element_id = element.id
)
;
There is a typo in your WHERE clause - one of the ids is 2 ("blue") instead of 3 ("brown"). It should be
WHERE (relation.colour_id = 1 OR relation.colour_id = 3)
(or in shorter form:
WHERE relation.colour_id IN (1, 3)
).
Note however, that your current query - although after this fix it should work for your sample data - won't give you correct results in general. It will give you the elements associated with any of the specified colors. The correct solution to this is given in #Nikola's answer though.
without subselects, I would suggest:
SELECT
e.id AS id
FROM
element AS e
LEFT OUTER JOIN relation AS r ON r.element_id = e.id
GROUP BY e.id HAVING SUM(CASE WHEN r.colour_id = 1 THEN 1 ELSE 0 END ) = 0
ORDER BY e.id ASC;
after this you can select the elements by id.
I have 2 related tables:
messages
--------
mid subject
--- -----------------
1 Hello world
2 Bye world
3 The third message
4 Last one
properties
----------
pid mid name value
--- --- ---------------- -----------
1 1 read false
2 1 importance high
3 2 read false
4 2 importance low
5 3 read true
6 3 importance low
7 4 read false
8 4 importance high
And I need to get from messages using the criteria on the properties table.
Eg: if I have a criteria like return unread (read=false) high prio (importance=high) messages it should return
mid subject
--- -----------------
1 Hello world
4 Last one
How could I get this with a SELECT clause (MySQL dialect)?
In SQL, any expression in a WHERE clause can only reference one row at a time. So you need some way of getting multiple rows from your properties table onto one row of result. You do this with self-joins:
SELECT ...
FROM messages AS m
JOIN properties AS pRead
ON m.mid = pRead.mid AND pRead.name = 'read'
JOIN properties AS pImportance
ON m.mid = pImportance.mid AND pImportance.name = 'importance'
WHERE pRead.value = 'false' AND pImportance.value = 'high';
This shows how awkward it is to use the EAV antipattern. Compare with using conventional attributes, where one attribute belongs in one column:
SELECT ...
FROM messages AS m
WHERE m.read = 'false' AND m.importance = 'high';
By the way, both answers from #Abe Miessler and #Thomas match more mid's than you want. They match all mid's where read=false OR where importance=high. You need to combine these properties with the equivalent of AND.
I believe the query below will work.
UPDATE: #Gratzy is right, this query won't work, take a look at the structure changes I suggested.
SELECT DISTINCT m.id as mid, m.subject
FROM message as m
INNER JOIN properties as p
ON m.mid = p.mid
where (p.name = 'read' and p.value = 'false') or (p.name = 'importance' AND p.value = 'high')
The structure of your properties table seems a little off to me though...
Would it be possible to structure the table like this:
messages
--------
mid subject Read Importance
--- ----------------- --------- ------------
1 Hello world false 3
2 Bye world false 1
3 The third message true 1
4 Last one false 3
importance
----------
iid importanceName
--- --------------
1 low
2 medium
3 high
and use this query:
SELECT m.id as mid, m.subject
FROM message as m
where m.read = false AND m.importance = 3
Clearly, you are using an EAV (Entity-Attribute-Value) schema. One of the many reasons for avoiding such a structure is that it makes queries more difficult. However, for the example you gave, you could do something like:
Select ...
From messages As M
Where Exists (
Select 1
From Properties As P1
Where P1.mid = M.mid
And P1.name = 'unread' And P1.value = 'false'
)
And Exists (
Select 1
From Properties As P2
Where P2.mid = M.mid
And P2.name = 'importance' And P2.value = 'high'
)
A more succinct solution would be:
Select ...
From messages As M
Where Exists (
Select 1
From Properties As P1
Where P1.mid = M.mid
And ((P1.name = 'unread' And P1.value = 'false')
Or (P1.name = 'importance' And P1.value = 'high'))
Having Count(*) = 2
)
Select m.mid, m.subject
from properties p
inner join properties p1 on p.mid = p1.mid
inner join messages m on p.mid = m.mid
where
p.name = 'read'
and p.value = 'false'
and p1.name = 'importance'
and p2.value = 'high'
I prefer to put my filter criteria in the where clause and leave my join's to elements that are in both tables and are the actual criteria for the join.
Another way might be (untested) to use a derived table to hold the criteria that all messages must meet then use the standard relational division technique of double NOT EXISTS
SELECT mid,
subject
FROM messages m
WHERE NOT EXISTS
( SELECT *
FROM ( SELECT 'read' AS name,
'false' AS value
UNION ALL
SELECT 'importance' AS name,
'high' AS value
)
c
WHERE NOT EXISTS
(SELECT *
FROM properties P
WHERE p.mid = m.mid
AND p.name =c.name
AND p.value=c.value
)
)
If you want to keep your existing data model, then go with Bill Karwin's first suggestion. Run it with this select clause to understand what it's doing:
select m.*, r.value as read, i.value as importance
from message m
join properties r
on r.mid = m.mid and r.name = 'read'
join properties i
on i.mid = m.mid and i.name = 'importance'
where r.value = 'false' and i.value = 'high';
But if you go this way, there are a few constraints you should put in place to avoid storing and retrieving bad data:
A unique index on message(mid) and a unique index on properties(pid), both of which I'm sure you have already.
A unique index on properties(mid, name) so that each property can only be defined once for a message -- otherwise you may get duplicate results from your query. This will also help your query performance by allowing an index access for both joins.
I need a bit of help constructing a query that will let me filter the following data.
Table: MyTree
Id ParentId Visible
=====================
1 null 0
2 1 1
3 2 1
4 3 1
5 null 1
6 5 1
I expect the following result from the query:
Id ParentId Visible
=====================
5 null 1
6 5 1
That is, all the children of the hidden node should not be returned. What's more is that the depth of a hierarchy is not limited. Now don't answer "just set 2, 3 & 4 to visible=0" for non-obviuos reasons that is not possible... Like I'm fixing a horrible "legacy system".
I was thinking of something like:
SELECT *
FROM MyTree m1
JOIN MyTree m2 ON m1.ParentId = m2.Id
WHERE m1.Visible = 1
AND (m1.ParentId IS NULL OR m2.Id IS NOT NULL)
Sorry for any syntactical mistakes
But that will only filter the first level, right? Hope you can help.
Edit: Finished up the title, whoops. The server is a brand spanking new MSSQL 2008 server but the database is running in 2000 compatibility mode.
In SQL Server 2005+:
WITH q (id, parentid, visible) AS
(
SELECT id, parentid, visible
FROM mytree
WHERE id = 5
UNION ALL
SELECT m.id, m.parentid, m.visible
FROM q
JOIN mytree m
ON m.parentid = q.id
WHERE q.visible = 1
)
SELECT *
FROM q
I agree with #Quassnoi's focus on recursive CTEs (in SQL Server 2005 or later) but I think the logic is different to answer the original question:
WITH visall(id, parentid, visible) AS
(SELECT id, parentid, visible
FROM mytree
WHERE parentid IS NULL
UNION ALL
SELECT m.id, m.parentid, m.visible & visall.visible AS visible
FROM visall
JOIN mytree m
ON m.parentid = visall.id
)
SELECT *
FROM visall
WHERE visall.visible = 1
A probably more optimized way to express the same logic should be to have the visible checks in the WHERE as much as possible -- stop recursion along invisible "subtrees" ASAP. I.e.:
WITH visall(id, parentid, visible) AS
(SELECT id, parentid, visible
FROM mytree
WHERE parentid IS NULL AND visible = 1
UNION ALL
SELECT m.id, m.parentid, m.visible
FROM visall
JOIN mytree m
ON m.parentid = visall.id
WHERE m.visible = 1
)
SELECT *
FROM visall
As usual with performance issues, benchmarking both versions on realistic data is necessary to decide with confidence (it also helps to check that they do indeed produce identical results;-) -- as DB engines' optimizers sometimes do strange things for strange reasons;-).
I think Quassnoi was close to what the questioner wants, but not quite. I think this is what the questioner is looking for (SQL Server 2005+):
WITH q (id) AS
(
SELECT id
FROM mytree
WHERE parentid is null and visible=1
UNION ALL
SELECT m.id
FROM q
JOIN mytree m
ON m.parentid = q.id
WHERE q.visible = 1
)
SELECT *
FROM q
Common Table Expressions are great for this kind of work.
I don't think what you need is possible from a single query. This looks more like something to do from code and still it will require multiple queries to DB.
If you really need to do it from SQL I think your best bet would be to use a cursor and build a table with hidden IDs. If data doesn't change often you might keep that 'temporary' table as a kind of cache.
Edit: I stand corrected (for SQL 2005) and also learned something new today :)