The following sql query below produces the specified result.
select product.product_no,product_type,salesteam.rep_name,salesteam.SUPERVISOR_NAME
from product
inner join salesteam
on product.product_rep=salesteam.rep_id
ORDER BY product.Product_No;
However my intensions are to further produce a more detailed result which will include all the attributes in the PRODUCT table. my approach is to list all the attributes in the first line of the query.
select product.product_no,product.product_date,product.product_colour,product.product_style,
product.product_age product_type,salesteam.rep_name,salesteam.SUPERVISOR_NAME
from product
inner join salesteam
on product.product_rep=salesteam.rep_id
ORDER BY product.Product_No;
Is there another way it can be done instead of listing all the attributes of PRoduct table one by one?
You can use * to select all columns from all tables, or you can use [table/alias].* to select all columns from the specified table. In your case, you can use product.*:
select product.*,salesteam.rep_name,salesteam.SUPERVISOR_NAME
from product
inner join salesteam
on product.product_rep=salesteam.rep_id
ORDER BY product.Product_No;
It is important to note that you should only do this if you are 100% sure you need every single column, and always will. There are performance implications associated with this; if you're selecting 100 columns from a table when you really only need 4 or 5 of them, you're adding a lot of overhead to the query. The DBMS has to work harder, and you're also sending more data across the wire (if your database is not on the same machine as your executing code).
If any columns are later added to the product table, those columns will also be returned by this query in the future.
select
product.*,
salesteam.rep_name,
salesteam.SUPERVISOR_NAME
from product inner join salesteam on
product.product_rep=salesteam.rep_id
ORDER BY
product.Product_No;
This should do.
You can write like this
select P.* --- all Product columns
,S.* --- all salesteam columns
from product P
inner join salesteam S
on P.product_rep=S.rep_id
ORDER BY P.Product_No;
Related
We're currently starting SQL in school ... so I'm very beginner.
Now we got a task that says:
Write a SQL-query which gives the same output like the following query. Use cross joins.
SELECT PRODUCT_NAME, QUANTITY_ON_HAND, WAREHOUSE_NAME
FROM WAREHOUSES
NATURAL JOIN INVENTORIES
NATURAL JOIN PRODUCT_INFORMATION
ORDER BY PRODUCT_NAME;
Now I don't know what to do. For me it doesn't make sense to replace natural join by cross join or isn't even possible?!
Please help.
Diagram:
The cross join can be seen also as a cartesian product: so every row of the first table is combined with a row on the second one, so the resulting number of rows will be rows(TableA) * rows(TableB).
To emulate a natural join with a cross join you'll need to compare the foreign/primary key of the different tables to see if they are the same like this:
SELECT PRODUCT_NAME, QUANTITY_ON_HAND, WAREHOUSE_NAME
FROM WAREHOUSES
CROSS JOIN INVENTORIES
CROSS JOIN PRODUCT_INFORMATION
WHERE WAREHOUSES.WAREHOUSES_ID = INVENTORIES.WAREHOUSE_ID AND
INVENTORIES.PRODUCT_ID = PRODUCT_INFORMATION.PRODUCT_ID
ORDER BY PRODUCT_NAME;
If you need more information about cross-join or natural join.
If it can help you try to think at it like this:
First you create a table with all the possible combination of rows
between the three tables
Than you start compare on each row the common and repetitive field, you've on each row 2 PRODUCT_ID and WAREHOUSE_ID columns, each of them coming from his specific table (try to execute the query taking all the columns with * to see this).
After that you take only the rows where the 2 type of columns have the same value (Emulating a natural join)
You're just doing a normal join....with extra steps.
I have the following query that uses joins to join multiple tables
select DISTINCT
tblArticles.Article_Title,
tblArticles.Article_img,
tblArticles.Article_Content,
tblArticles.Article_Date_Created,
tblArticles.Article_Sequence,
tblWriters.Writer_Name,
tblTypes.Article_Type_Name,
tblimages.image_path as "Extra images"
from tblArticles inner join tblWriters
on tblArticles.Writer_ID_Fkey = tblWriters.Writer_ID inner join
tblArticleType on tblArticles.Article_ID = tblArticleType.Article_ID_Fkey inner join
tblTypes on tblArticleType.Article_Type_ID_Fkey = tblTypes.Article_Type_ID left outer join tblExtraImages
on tblArticles.Article_ID = tblExtraImages.Article_ID_Fkey left outer join tblimages
on tblExtraImages.image_id_fkey = tblimages.image_id
order by tblArticles.Article_Sequence, tblArticles.Article_Date_Created;
And I get the following results:
If an article has more than one type_name then I will get repeated columns for the rest of the records. Is there another way of joining these tables that would prevent that from happening?
The simplest method is to just remove column Article_Type_Name from the select clause. This allows SELECT DISTINCT to identify the rows as duplicates, and eliminate them.
Another option is to use an aggregation function on the column. In recent SQL Server versions, STRING_AGG() comes handy (you can also use MIN() or MAX()):
select
tblArticles.Article_Title,
tblArticles.Article_img,
tblArticles.Article_Content,
tblArticles.Article_Date_Created,
tblArticles.Article_Sequence,
tblWriters.Writer_Name,
string_agg(tblTypes.Article_Type_Name, ',')
within group(order by tblTypes.Article_Type_Name) Article_Type_Name_List,
tblimages.image_path as Extra_Images
from ..
group by
tblArticles.Article_Title,
tblArticles.Article_img,
tblArticles.Article_Content,
tblArticles.Article_Date_Created,
tblArticles.Article_Sequence,
tblWriters.Writer_Name,
tblimages.image_path
What you're seeing here is a Cartesian product; you've joined Tables in such a way that multiple rows from one side match with rows from the other
If you don't care about the article_type, then group the other columns and take the max(article_type), or omit it in a subquery that selects distinct records, not including the article type column, from the table that contains article type). If your SQLS is recent enough and you want to know all the article types you could STRING_AGG them into a csv list
Ultimately what you choose to do depends on what you want them for; filter the rows out, or group them down
I have three tables
PackingLists
ItemsToPackingLists
Items
I would like to have a list of all PackingLists with the Number of items per PackingList and the WeightInGramms for the PackingList.
I wrote the following query, but it gives wrong results. I guess I have to arrange the joins somehow different.
Any help how to refactor the query is appreciated.
SELECT p.ID,
p.NameOfPackingList,
COUNT(ItemsToP.ItemID) AS NumberOfDifferentItems,
SUM(items.WeightInGrams * ItemsToP.Quantity) AS WeightInGramms
FROM PackingLists AS p
LEFT OUTER JOIN ItemsToPackingLists AS ItemsToP
ON (ItemsToP.PackingListID = p.ID)
LEFT OUTER JOIN Items AS items
ON (ItemsToP.ItemID = items.ID)
GROUP BY p.ID,p.NameOfPackingList
Not really clear what you want to get, but two options to check.
Use COUNT(Distinct ItemsToP.ItemID) instead of COUNT(ItemsToP.ItemID), you might including the same item twice in one package (with different quantities), and naming of the col 'NumberOfDifferentItems' suggest using distinct as well.
However, your question is 'Number of items per PackingList'. To my understanding you should sum the quantities, SUM(ItemsToP.Quantity) instead of counting the IDs.
I just hit a wall with my SQL query fetching data from my MS SQL Server.
To simplify, say i have one table for sales, and one table for customers. They each have a corresponding userId which i can use to join the tables.
I wish to first SELECT from the sales table where say price is equal to 10, and then join it on the userId, in order to get access to the name and address etc. from the customer table.
In which order should i structure the query? Do i need some sort of subquery or what do i do?
I have tried something like this
SELECT *
FROM Sales
WHERE price = 10
INNER JOIN Customers
ON Sales.userId = Customers.userId;
Needless to say this is very simplified and not my database schema, yet it explains my problem simply.
Any suggestions ? I am at a loss here.
A SELECT has a certain order of its components
In the simple form this is:
What do I select: column list
From where: table name and joined tables
Are there filters: WHERE
How to sort: ORDER BY
So: most likely it was enough to change your statement to
SELECT *
FROM Sales
INNER JOIN Customers ON Sales.userId = Customers.userId
WHERE price = 10;
The WHERE clause must follow the joins:
SELECT * FROM Sales
INNER JOIN Customers
ON Sales.userId = Customers.userId
WHERE price = 10
This is simply the way SQL syntax works. You seem to be trying to put the clauses in the order that you think they should be applied, but SQL is a declarative languages, not a procedural one - you are defining what you want to occur, not how it will be done.
You could also write the same thing like this:
SELECT * FROM (
SELECT * FROM Sales WHERE price = 10
) AS filteredSales
INNER JOIN Customers
ON filteredSales.userId = Customers.userId
This may seem like it indicates a different order for the operations to occur, but it is logically identical to the first query, and in either case, the database engine may determine to do the join and filtering operations in either order, as long as the result is identical.
Sounds fine to me, did you run the query and check?
SELECT s.*, c.*
FROM Sales s
INNER JOIN Customers c
ON s.userId = c.userId;
WHERE s.price = 10
Okay, I'm relatively new to the more advanced uses of SQL Server.
I have several tables that I need to gather informations from, and several of these tables links to other tables where I need a specific information. As a result, I just want one row with all the information, preferential named with aliases.
For example:
Tab_Transcoders:
ID, VideoCamID, InputStreamID, OutputStreamID.
where InputStream links to another table where I need the row of the matching ID, where in this row are other ID's (e.g. StreamType_ID that belongs to a third table containing ID_StreamType and Description etc.)
Same with OutputStreamID, same with VideoCamID.
In the end, I need a row containing for example:
ID, VideoCamID, InputStreamID, InputStreamType, InputStreamTypeDesc,
OutputStreamID, OutputStreamType, OutputStreamDesc, VideoCamID, etc. etc. etc.
It is important for me that I can set aliases, as for example InputStreamID & OutputStreamID links to the same table where all my Streams are listed (with IP's, Descs..)
I can accomplish this with doing like 100 SELECTS & SUBSELECTS, but I don't think that's an appropriate way.
I read some informations about things like CURSOR, UNION, FETCH, JOIN etc. etc.. but I don't know which one I have to use for my purpose.
eli
I think you want something like the following....
Select
t.ID,
t.VideoCamID,
i.InputStreamID,
is.StreamType as InputStreamType,
is.StreamDesc as InputStreamDesc,
o.OutputStreamID,
os.StreamType as OutputStreamType,
os.StreamDesc as OutputStreamDesc,
v.VideoCamID
from
Tab_Transcoders t
inner join InputStreams i on i.InputStreamID=t.InputStreamId
inner join Streams is on is.StreamId=i.StreamId
inner join OutputStreams o on o.OutputStreamId=t.OutputStreamId
inner join Streams os on os.StreamID=o.StreamId
inner join VideoCams v on v.VideoCamId=t.VideoCamID
If there is a defined relationship between your tables, then Use Join.
e.g Customer Order
Order will have customer Id
Select Order.ID,Order.Quantity, Order.CustomerId, Customer.FullName, Customer.Address
From Orders Order
Join
Customer
On
Order.CustomerId = Customer.CustomerId
First start by getting data from two tables using the join and then if it works as per your requirement, add another required table in the join.
Read about SQl JOINS.. It is fairly simple.
I will recommend reading you some of the articles around CTE aka Common Table Expression.
Refer http://msdn.microsoft.com/en-us/library/ms190766%28v=sql.105%29.aspx.
Apart from this never use subqueries. Try to use inner join / any other join if possible.