I have two tables, tabSparePart and tabSparePartCategory. Every spare part belongs to a spare part category. I need all spare parts that belong to a specific category. But the problem is that a spare part category could be a "subcategory" of another, they reference each other (the "main categories" have 'null' in this FK column).
Let's say I need all spare parts with fiSparePartCategory=1 and all spare parts that belong to a category that is a "subcategory" of category=1.
How to write the SQL query that returns all spare parts regardless of how many levels of subcategories there are. I hope you understand my requirement.
The following is an illustration of what I have. How to make it dynamic so that it works regardless of the number of subcategories?
Thanks, Tim
Link to image: http://www.bilder-hochladen.net/files/4709-lg-jpg.html
EDIT: Following is an other static approach which works when there is only one level of subcategory:
SELECT SparePartName
FROM tabSparePart
WHERE (fiSparePartCategory IN
(SELECT idSparePartCategory
FROM tabSparePartCategory
WHERE (idSparePartCategory = 1) OR
(fiSparePartCategory = 1)))
You can use a recursive Common Table Expression for this.
In your case, you would need to get all sparepart category ids for a specific main category id and join that with the spareparts. Something like this:
WITH SparePartCategories(CategoryId) AS
(
SELECT c.idSparePartCategory
FROM tabSparePartCategory c
WHERE c.idSparePartCategory = 1
UNION ALL
SELECT c.idSparePartCategory
FROM tabSparePartCategory c
JOIN SparePartCategories parent ON c.fiSparePartCategory = parent.CategoryId
)
SELECT sp.SparePartName
FROM tabSparePart sp
JOIN SparePartCategories spc ON sp.fiSparePartCategory = spc.CategoryId
Related
I'm writing some SQL code based on my tables but don't want to miss any edge cases. I'm wondering how do you check if there's a one to many relationship between two tables in SSMS
SELECT *
FROM Houses
JOIN Addresses
on Houses.Id = Addresses.HouseId
Unfortunately the data when queried doesn't give me any insight.
What I tried to do:
Checked table dependencies but that didn't give me any insight. It shows addresses are dependencies but no relationship details.
May I ask, is it possible to determine if one to one via SSMS?
You can run a query to determine how many values each house in the two tables. Well, in this case, we'll assume it is the primary key of houses and the values of HouseId are valid ids:
SELECT num_addresses, COUNT(*)
FROM (SELECT h.Id, COUNT(a.HouseId) as num_addresses
FROM Houses h LEFT JOIN
Addresses a
ON h.Id = a.HouseId
GROUP BY h.Id
) ha
GROUP BY num_addresses;
Then interpret the results:
If the only row returned has num_addresses of 1, then you have a 1-1 relationship.
If two rows are returns with values of 0 and 1, then you have a 1/0-1 relationship.
If multiple rows are returned and the minimum is 1 then you have a 1-n.
If multiple rows are returned and the minimum value is 0, then you have a 0-n.
You could extend this for more general relationships, but this answers the question you asked here.
The relationship between tables is shown by things called 'DATABASE - DIAGRAM'
Here is document about how to create database - diagram in SSMS.
How to create database diagram SSMS
Gordon Linoff response is perfect for the helicopter view -
To get all records side by side simply select all columns from both tables side by side with the left join
SELECT Houses.*, Address.*
FROM Houses
left JOIN Addresses on Addresses.HouseId = Houses.Id
union all
SELECT Houses.*, Address.*
FROM Addresses
left JOIN Houses on Houses.Id = Addresses.HouseId
Microsoft have implemented a reduced code method to do the same but I have not explored it so could not comment
https://learn.microsoft.com/en-us/sql/odbc/reference/develop-app/outer-joins?view=sql-server-ver15
What will be apparent is you will see Houses.ID and Addresses.HouseID side by side - An empty value in either means that the relevant table does not have a record for the relevant HouseID or ID
You can then cherry pick those edge case records as you see fit
I want to count how many people are applied for each category in my database and put all of those counts in one table. I don't have exact idea how should I do that. I've done it already like this but I want to have all in one query, and not to do it like this for each category.
select
count(cc.fk_id_candidates) as 'category A'
from candidate_category cc, candidate c, category cat
where c.id=cc.fk_id_candidates and cc.fk_id_category=cat.id and category.name='A';
From that code I get number of people applied for category A as an output, which is correct, but I just need the same info for other categories too. I tried with case but it's not working right.
Thank you.
You would typically add a group by clause on the category name and/or id:
select cat.category.name, count(*) cnt
from candidate_category cc
inner join candidate c on c.id = cc.fk_id_candidates and
inner join category cat on cc.fk_id_category = cat.id
group by cat.id, cat.category.name;
Note that I changed your query to use standard joins (with the on keyword) rather than implicit joins (with commas in the from clause and conditions in the where clause) - this old syntax should not be used in new code.
As i understand you have three tables:
- candidate_category cc,
- candidate c,
- category cat
Also, you have Created below relationship using the REFERENCES:
where c.id=cc.fk_id_candidates
and cc.fk_id_category=cat.id
and category.name='A;
Now, you must have all the three tables in one table already and you can view it by:
and this is very important step to find a common column where you can filter it and find the proper data you want.
Select *
from candidate_category cc,
candidate c,
category cat
where c.id=cc.fk_id_candidates
and cc.fk_id_category=cat.id
I have a data model such that items can have many-to-many relationships with other items in the same table using a second table to define relationships. Let's call the primary table items, keyed by item_id and the relationships table item_assoc with columns item_id and other_item_id and assoc_type. Generally, you might use a union to pick up on relationships that may be defined in either direction in the item_assoc table, but you would wind up repeating other parts of the same query just to be sure to pick up associations defined in either direction.
Let's say that you're trying to put together a fairly complex query similar to the following where you want to find a list of items that have related items that COULD have associated cancellation items, but select those that do not have cancellation items:
select
orig.*
from items as orig
join item_assoc as orig2related
on orig.item_id = orig2related.item_id
join items as related
on orig2related.other_item_id = related.item_id
and orig2related.assoc_type = 'Related'
left join item_assoc as related2cancel
on related.item_id = related2cancel.item_id
left join items as cancel
on related2cancel.other_item_id = cancel.item_id
and related2cancel.assoc_type = 'Cancellation'
where cancel.item_id is null
This query obviously only picks up items whose relationships are defined in one direction. For a less complex query, I might solve this by adding a union at the bottom for every permutation of the reverse relationships, but I think that would make the query unnecessarily long and hard to understand.
Is there a way I can define both directions of each relationship without repeating the other parts of the query?
A UNION within item_assoc could help. Assuming you have a DB without a WITH clause you would have to define a view
CREATE VIEW bidirec_item_assoc AS
(
SELECT item_id, other_item_id, assoc_type, 1 as direction FROM item_assoc
UNION
SELECT other_item_id, item_id, assoc_type, 2 as direction FROM item_assoc
)
You can now use bidirec_item_assoc in your queries where you have used items_assoc before.
Edited Out: You could add columns for direction and relationtype, of course
Simplify, simplify, simplify: Don't involve tables in the query that aren't needed.
The following query should be equivalent to your sample query and more expressive of your intent:
select i.*
from items i
where not exists ( select *
from item_assoc r
join item_assoc c on c.item_id = r.item_id
and c.assoc_type = 'Cancellation'
where r.item_id = i.item_id
and r.assoc_type = 'Related'
)
It should select the set of items that aren't related to an item that has been cancelled. There's not need to join against the items table 3 times.
Further, your original query will have duplicate rows: every row in the first item table (orig) will be duplicated once for every related item.
I have searched high and low and have tried for hours to manipulate the various other queries that seemed to fit but I've had no joy.
I have several Tables in Microsoft SQL Server 2005 that I'm trying to join, an example of which is:
Company Table (Comp_CompanyId, Comp_Name)
GroupCode_Link Table (gcl_c_groupcodelinkid, gcl_c_groupcodeid, gcl_c_companyid)
GroupCode Table (grp_c_groupcodeid, grp_c_groupcode, grp_c_name)
ItemCode Table (itm_c_itemcodeid, itm_c_name, itm_c_itemcode, itm_c_group)
ItemCode_Link Table (icl_c_itemcodelinkid, icl_c_companyid, icl_c_groupcodeid, icl_c_itemcodeid)
I'm using Link Tables to associate a Group to a Company, and an Item to a Group, so a Company could have multiple groups, with multiple items in each group.
Now, I'm trying to create an Advanced Find Function that will allow a user to enter, for example, an Item Code and the result should display those companies that have that item, sounds nice and simple!
However, I haven't done something right, if I use the following query ' if the company has this item OR this item, display it's name', I get the company appearing twice in the result set, once for each item.
What I need is to be able to say is:
"Show me a list of companies that have these items (displaying each company only once!)"
I've had a go at using COUNT, DISTINCT and HAVING but have failed on each as my query knowledge isn't up to it!
First, from your description it sounds like you might have a problem with your E-R (entity-relationship) model. Your description tells me that your E-R model looks something like this:
Associative entities (CompanyGroup, GroupItem) exist to implement many-to-many relationships (since many-to-many isn't supported directly by relational databases).
Nothing wrong with that if a group can exist within multiple companies or an item across multiple groups. It would seem more likely that, at least, each group is specific to a company (I can see items existing across multiple companies and/or groups: more than one company retails, for instance, Cuisinart food processors). If that is the case, a better E-R model would be to make each group a dependent entity with a CompanyID that is a component of its primary key. It's a dependent entity because the group doesn't have an independent existence: it's created by/on behalf of and exists for its parent company. If the company goes away, the group(s) tied to it go away. No your E-R model looks like this:
From that, we can write the query you need:
select *
from Company c
where exists ( select *
from GroupItem gi
where gi.ItemID in ( desired-itemid-1 , ... , desired-itemid-n )
and gi.CompanyID = c.CompanyID
)
As you can see, dependent entities are a powerful thing. Because of the key propagation, queries tend to get simpler. With the original data model, the query would be somewhat more complex:
select *
from Company c
where exists ( select *
from CompanyGroup cg
join GroupItem gi on gi.GroupId = cg.GroupID
where gi.ItemID in ( desired-itemid-1 , ... , desired-itemid-n )
and cg.CompanyID = c.CompanyID
)
Cheers!
SELECT *
FROM company c
WHERE (
SELECT COUNT(DISTINCT icl_c_itemcodeid)
FROM GroupCode_Link gl
JOIN ItemCode_Link il
ON il.icl_c_groupcodeid = gcl_c_groupcodeid
WHERE gl.gcl_c_companyid = c.Comp_CompanyId
AND icl_c_companyid = c.Comp_CompanyId
AND icl_c_itemcodeid IN (#Item1, #Item2)
) >= 2
Replace >= 2 with >= 1 if you want "any item" instead of "all items".
If you need to show companies that have item1 AND item2, you can use Quassnoi's answer.
If you need to show companies that have item1 OR item2, then you can use this:
SELECT
*
FROM
company
WHERE EXISTS
(
SELECT
icl_c_itemcodeid
FROM
GroupCode_Link
INNER JOIN
ItemCode_Link
ON icl_c_groupcodeid = gcl_c_groupcodeid
AND icl_c_itemcodeid IN (#item1, #item2)
WHERE
gcl_c_companyid = company.Comp_CompanyId
AND
icl_c_companyid = company.Comp_CompanyId
)
I would write something like the code below:
SELECT
c.Comp_Name
FROM
Company AS c
WHERE
EXISTS (
SELECT
1
FROM
GroupCode_Link AS gcl
JOIN
ItemCode_Link AS icl
ON
gcl.gcl_c_groupcodeid = icl.icl_c_groupcodeid
JOIN
ItemCode AS itm
ON
icl.icl_c_itemcodeid = itm.itm_c_itemcodeid
WHERE
c.Comp_CompanyId = gcl.gcl_c_companyid
AND
itm.itm_c_itemcode IN (...) /* here provide list of one or more Item Codes to look for */
);
but I see there's a icl_c_companyid column in the ItemCode_Link so using GroupCode_Link table is not necessary?
I'm taking a database course this semester, and we're learning SQL. I understand most simple queries, but I'm having some difficulty using the count aggregate function.
I'm supposed to relate an advertisement number to a property number to a branch number so that I can tally up the amount of advertisements by branch number and compute their cost. I set up what I think are two appropriate new views, but I'm clueless as to what to write for the select statement. Am I approaching this the correct way? I have a feeling I'm over complicating this bigtime...
with ad_prop(ad_no, property_no, overseen_by) as
(select a.ad_no, a.property_no, p.overseen_by
from advertisement as a, property as p
where a.property_no = p.property_no)
with prop_branch(property_no, overseen_by, allocated_to) as
(select p.property_no, p.overseen_by, s.allocated_to
from property as p, staff as s
where p.overseen_by = s.staff_no)
select distinct pb.allocated_to as branch_no, count( ??? ) * 100 as ad_cost
from prop_branch as pb, ad_prop as ap
where ap.property_no = pb.property_no
group by branch_no;
Any insight would be greatly appreciated!
You could simplify it like this:
advertisement
- ad_no
- property_no
property
- property_no
- overseen_by
staff
- staff_no
- allocated_to
SELECT s.allocated_to AS branch, COUNT(*) as num_ads, COUNT(*)*100 as ad_cost
FROM advertisement AS a
INNER JOIN property AS p ON a.property_no = p.property_no
INNER JOIN staff AS s ON p.overseen_by = s.staff_no
GROUP BY s.allocated_to;
Update: changed above to match your schema needs
You can condense your WITH clauses into a single statement. Then, the piece I think you are missing is that columns referenced in the column definition have to be aggregated if they aren't included in the GROUP BY clause. So you GROUP BY your distinct column then apply your aggregation and math in your column definitions.
SELECT
s.allocated_to AS branch_no
,COUNT(a.ad_no) AS ad_count
,(ad_count * 100) AS ad_cost
...
GROUP BY s.allocated_to
i can tell you that you are making it way too complicated. It should be a select statement with a couple of joins. You should re-read the chapter on joins or take a look at the following link
http://www.sql-tutorial.net/SQL-JOIN.asp
A join allows you to "combine" the data from two tables based on a common key between the two tables (you can chain more tables together with more joins). Once you have this "joined" table, you can pretend that it is really one table (aliases are used to indicate where that column came from). You understand how aggregates work on a single table right?
I'd prefer not to give you the answer so that you can actually learn :)