Put into a simplified way, I have three tables: Products, ProductsCounties, and Counties. We can only sell certain products in certain counties, so there is a many-to-many relationship between Products and Counties with ProductsCounties.
To make it even simpler to ask (because I'm using split strings from a comma separated list in a stored procedure... among magic), let's say I just have a table called WantedCounties with CountyName's County1, County2, and County3 as records. This is basically the result of the split string function based on what I give it. My problem is, I want to give three counties (think WantedCounties is going to be what I'm giving) and that Product has to be available in ALL THREE and not just one, hence why my IN statement fails here.
SELECT DISTINCT p.* FROM Products p
JOIN ProductsCounties pc ON pc.ProductId = p.ProductId
JOIN Counties c ON pc.CountyId = c.CountyId
WHERE c.CountyName IN (SELECT CountyName FROM WantedCounties)
This is as much as I can narrow down my problem for sake of making it easy to ask. Does anyone know how to do this? I want only products that have a relationship with every single county given, not just one match IN the subquery.
I think my issue is I can't grasp how to deal with there being multiple rows being selected because of each county match on the join.
I have also tried something along the lines of = ALL (SELECT CountyName FROM WantedCounties) to no avail.
Edit: I found the solution here. I had to include this:
GROUP BY --All my refrences
HAVING COUNT(DISTINCT c.CountyName) = (
SELECT CountyName
FROM WantedCounties)
)
This only returns products that have a match in every County in WantedCounties. So there had to be all 3 counties in my results to match the 3 counties in WantedCounties in order for it to say "that's all of them."
I found the solution here. I had to include this:
GROUP BY --All my refrences
HAVING COUNT(DISTINCT c.CountyName) = (
SELECT CountyName
FROM WantedCounties)
)
This only returns products that have a match in every County in WantedCounties. So there had to be all 3 counties in my results to match the 3 counties in WantedCounties in order for it to say "that's all of them."
Related
I have two tables I need information from, Products and Suppliers. Both these tables have a SupplierID column I am trying to use to join them together to retrieve the right info.
The output I need is SupplierID and ContactName from the Suppliers table. The correct output should contain only two suppliers, so I attempted something like this, but ran into a conversion error converting nvarchar value to a data type int. I am not supposed to count how many products they supply but aggregate functions seem like the best method to me.
SELECT TOP 2 ContactName, COUNT(Products.SupplierID) AS Supply
FROM Products
LEFT JOIN Suppliers ON Suppliers.ContactName = Products.SupplierID
GROUP BY Products.SupplierID, Suppliers.ContactName
ORDER BY Supply;
I have tried many different queries but none will work. I am confused on how to join these tables without running into errors. All the products have a unique ProductID as well. The correct output should look something like this:
7 John Smith
12 John Sample
Both these tables have a SupplierID column I am trying to use to join them together to retrieve the right info
If so, you should be joining on that column accross tables.
Also, it is a good practice to use table aliases and prefix each column with the table it belongs to.
Another remark is that if you want suppliers that sell the most different products, then you want to order by descending count (not ascending).
Finally, if you want to left join, then you should start from the suppliers and then bring in the products, not the other way around.
Consider:
select top 2
s.SupplierID,
s.ContactName,
COUNT(*) as Supply
from Suppliers s
left join Products p on p.SupplierID = s.SupplierID
group by s.SupplierID, s.ContactName
order by Supply desc;
You're currently joining on two different fields:
on Suppliers.ContactName = Products.SupplierID
Presumably this should be as follows?
on Suppliers.SupplierID = Products.SupplierID
What my issue is:
I am constantly returning multiple values when I don't expect to. I am attempting to get a specific climate, determined by the state, county, and country.
What I've tried:
The code given below. I am unsure as to what is wrong with it specifically. I do know that it is returning multiple values. But why? I specify that STATE_ABBREVIATION = PROV_TERR_STATE_LOC and with the inner joins that I do, shouldn't that create rows that are similar except for their different CLIMATE_IDs?
SELECT
...<code>...
(SELECT locations.CLIMATE_ID
FROM REF_CLIMATE_LOCATION locations, SED_BANK_TST.dbo.STATIONS stations
INNER JOIN REF_STATE states ON STATE_ID = states.STATE_ID
INNER JOIN REF_COUNTY counties ON COUNTY_ID = counties.COUNTY_ID
INNER JOIN REF_COUNTRY countries ON COUNTRY_ID = countries.COUNTRY_ID
WHERE STATE_ABBREVIATION = PROV_TERR_STATE_LOC) AS CLIMATE_ID
...<more code>...
FROM SED_BANK_TST.dbo.STATIONS stations
I've been at this for hours, looking up different questions on SO, but I cannot figure out how to make this subquery return a single value.
All those inner joins don't reduce the result set if the IDs you're testing exist in the REF tables. Apart from that you're doing a Cartesian product between locations and stations (which may be an old fashioned inner join because of the where clause).
You'll only get a single row if you only have a single row in the locations table that matches a single row in the stations table under the condition that STATE_ABBREVIATION = PROV_TERR_STATE_LOC
Your JOINs show a hierarchy of locations: Country->State->County, but your WHERE clause only limits by the state abbreviation. By joining the county you'll get one record for every county in that state. You CAN limit your results by taking the TOP 1 of the results, but you need to be very careful that that's really what you want. If you're looking for a specific county, you'll need to include that in the WHERE clause. You get some control with the TOP 1 in that it will give the top 1 based on an ORDER BY clause. I.e., if you want the most recently added, use:
SELECT TOP 1 [whatever] ORDER BY [DateCreated] DESC;
For your subquery, you can do something like this:
SELECT TOP 1
locations.CLIMATE_ID
FROM REF_CLIMATE_LOCATION locations ,
SED_BANK_TST.dbo.STATIONS stations
INNER JOIN REF_STATE states ON STATE_ID = states.STATE_ID
INNER JOIN REF_COUNTY counties ON COUNTY_ID = counties.COUNTY_ID
INNER JOIN REF_COUNTRY countries ON COUNTRY_ID = countries.COUNTRY_ID
WHERE STATE_ABBREVIATION = PROV_TERR_STATE_LOC
Just be sure to either add an ORDER BY at the end or be okay with it choosing the TOP 1 based on the "natural order" on the tables.
If you are expecting to have a single value on your sub-query, probably you need to use DISTINCT. The best way to see it is you run your sub-query separately and see the result. If you need to include other columns from the tables you used, you may do so to check what makes your result have multiple rows.
You can also use MAX() or MIN() or TOP 1 to get a single value on the sub-query but this is dependent to the logic you want to achieve for locations.CLIMATE_ID. You need to answer the question, "How is it related to the rest of the columns retrieved?"
I have a table with customers, and a table with cities.
In the customers table, the city_id is related to the id_city of the cities table.
Other fields in the tables
customers: name, surname
cities: ext_code, description, address_code
The problem is that I have thousands of customers records related to cities in which the ext_code is not present.
The cities table, elsewhere, contains a lot of duplicated records; in the duplicated sets only one record has a valid ext_code.
The problem is: substitute the city_id with a id_city that contains a valid ext_code. The only fields to evaluate to group cities are address_code or description.
Any suggestion?
If the
only fields to evaluate to group cities are address_code or
description
then that's what you should use to join your data on while filtering out the non "valid ext_code" that you mentioned.
Here is a crude way to do a one time update of customer.
You will need to tweak the code to make it work with your system, but that should be easy enough.
UPDATE Customer
SET CityID =
(
--This bit will find cities that look like the one we already have,
SELECT TOP 1 CityID
FROM City AS X
WHERE X.AddressCode = City.AddressCode
OR X.Description = City.Description
ORDER BY X.ExtCode DESC --This puts nulls last!
)
FROM Customer
INNER JOIN City ON City.CityID = Customer.CityID
In my tables I have for example
CountyID,County and CityID in the county table and in the city table I have table I have for example
City ID and City
How do I create a report that pulls the County from the county table and pulls city based upon the cityid in the county table.
Thanks
Since this is quite a basic question, I'll give you a basic answer instead of the code to do it for you.
Where tables have columns that "match" each other, you can join them together on what they have in common, and query the result almost as if it was one table.
There are also different types of join based on what you want - for example it might be that some rows in one of the tables you're joining together don't have a corresponding match.
If you're sure that a city will definitely have a corresponding county, try inner joining the two tables on their matching column CityID and querying the result.
The obvious common link between both tables is CityID, so you'd be joining on that. I think you have the data organized wrong though, I'd put CountryID in the City table rather than CityID in the country table. Then, based on the CountryID selected, you can limit your query of the City table based on that.
To follow in context of Bridge's answer, you are obviously new to SQL and there are many places to dig up how to write them. However, the most fundamental basics you should train yourself with is always apply the table name or alias to prevent ambiguity and try to avoid using column names that might be considered reserved words to the language... they always appear to bite people.
That said, the most basic of queries is
select
T1.field1,
T1.field2,
etc with more fields you want
from
FirstTable as T1
where
(some conditional criteria)
order by
(some column or columns)
Now, when dealing with multiple tables, you need the JOINs... typically INNER or LEFT are most common. Inner means MUST match in both tables. LEFT means must match the table on the left side regardless of a match to the right... ex:
select
T1.Field1,
T2.SomeField,
T3.MaybeExistsField
from
SomeTable T1
Join SecondTable T2
on T1.SomeKey = T2.MatchingColumnInSecondTable
LEFT JOIN ThirdTable T3
on T1.AnotherKey = T3.ColumnThatMayHaveTheMatchingKey
order by
T2.SomeField DESC,
T1.Field1
From these examples, you should easily be able to incorporate your tables and their relationships to each other into your results...
I have a table B with cids and cities. I also have a table C that has these cids with extra information. I want to list all the cids in table C that are associated with ALL appearances of a given city in Table B.
My current solution relies on counting the number of times the given city appears in Table B and selecting only the cids that appear that many times. I don't know all the SQL syntax yet, but is there a way to select for this kind of pattern?
My current solution:
SELECT Agents.aid
FROM Agents, Customers, Orders
WHERE (Customers.city='Duluth')
AND (Agents.aid = Orders.aid)
AND (Customers.cid = Orders.cid)
GROUP BY Agents.aid
HAVING count(Agents.aid) > 1
It only works because I know right now with the HAVING statement.
Thanks for the help. I wasn't sure how to google this problem, since it's pretty specific.
EDIT: I'm pinpointing my problem a bit. I need to know how to determine if EVERY row in a table has a certain value for a field. Declaring a variable and counting the rows in a sub-selection and filtering out my results by IDs that appear that many times works, but It's really ugly.
There HAS to be a way to do this without explicitly count()ing rows. I hope.
Not an answer to your question, but a general improvement.
I'd recommend using JOIN syntax to join your tables together.
This would change your query to be:
SELECT Agents.aid
FROM Agents
INNER JOIN Orders
ON Agents.aid = Orders.aid
INNER JOIN Customers
ON Customers.cid = Orders.cid
WHERE Customers.city='Duluth'
GROUP BY Agents.aid
HAVING count(Agents.aid) > 1
What variant of SQL are you using?
To start with, you can (and should) use JOIN instead of doing it in the WHERE clause, e.g.,
select Agents.aid
from Agents
join Orders on Agents.aid = Orders.aid
join Customers on Customers.cid = Orders.cid
where Customers.city = 'Duluth'
group by Agents.aid
having count(Agents.aid) > 1
After that, I'm afraid I might be a little lost. Using the table names in your example query, what (in English, not pseudocode) are you trying to retrieve? For example, I think your sample query is retrieving the PK for all Agents that have been involved in at least 2 Orders involving Customers in Duluth.
Also, some table definitions for Agents, Orders, and Customers might help (then again, they might be irrelevant).
I'm not sure if I understood you problem, but I think the following query is what you want:
SELECT *
FROM customers b
INNER JOIN orders c USING (cid)
WHERE b.city = 'Duluth'
AND NOT EXISTS (SELECT 1
FROM customers b2
WHERE b2.city = b.city
AND b2.cid <> cid);
Probably you will need some indexes on these columns.