I am using Oracle via the SQL+ command line, i'm trying to display data from two different tables, but i require the use of a third table to determine what to display. Below is an image of my sample 3 tables.
Stack won't let me show my images in the question so here is a link:
I want to display the "Name","O_ID" and "Date" for each order. I'm quite new to SQL and this may have been answered before but i could not find it.
JOIN the tables:
SELECT
c.Name,
o.O_ID,
od.Date
FROM Customer AS c
INNER JOIN "Order" AS o ON c.C_ID = o.C_ID
INNER JOIN OrderDate AS od ON o.O_ID = od.O_ID;
What you are attempting to do is a very common practice and requires a INNER JOIN.
From a design perspective, the Order Date table shouldn't even exist. The date column should just reside within the Order table. I wrote the query based on that design:
SELECT
o.O_ID,
o.Date,
c.Name,
FROM
customer AS c
INNER JOIN order AS o ON c.C_ID = o.C_ID
Edit:
More on the issue of your design: A natural ordering of your data would be that there is 1 date for an order, not many dates for an order. Introducing another table to simply store the date allows for there to potentially be many dates associated with an order, which is simply unnatural.
Do a JOIN
select c.Name, o.O_ID, od.Date
from Customer c
inner join Order o on o.O_ID = c.C_ID
inner join OrderDate od on o.O_ID = od_ID
Doc: http://www.w3schools.com/sql/sql_join.asp
Related
I am struggling with a sql statement. I am hoping a guru can help a beginner out, currently I have multiple select in statements.. but think there is a better way as I have been stuck.
Below are the tables and pertinent columns in each table
country
-country_id
barcodes_banned_in_country
-barcode(varchar)
-country_id
-country_name
orders
-order_id
-country_name
item
-order_id
-item_id
-barcode(varchar)
The goal is to get all orders that are banned based off the barcode banned list.
Any help with this sql statement would be appreciated.
One option uses exists:
select o.*
from orders o
where exists (
select 1
from barcodes_banned_in_country bic
inner join item i on i.barcode = bic.barcode
where i.order_id = o.order_id and bic.country_name = o.country_name
)
This brings all orders whose at least one item have a barcode that is banned in the order's country.
If, on the other hand, you want the list of the banned barcodes per order, then you can join and aggregate:
select o.order_id, o.country_name, listagg(i.barcode, ',') banned_barcodes
from orders o
inner join item i
on i.order_id = o.order_id
inner join barcodes_banned_in_country bic
on i.barcode = bic.barcode
and bic.country_name = o.country_name
group by o.order_id, o.country_name
Note that, as commented by MT0, you should really be storing the id of the country in orders rather than the country name. Accordingly, you wouldn't need the country name in the banned barcodes table.
I have to create a view that joins together all of the columns in the CUSTOMERS, ORDERS, ORDERDETAILS, EMPLOYEES, PAYMENTS and PRODUCTS tables.
the schema for the table is below
I tried the following query, though I am at a loss how to solve the above question :
create view orders_view AS
select *
from sys.customers c
left JOIN EMPLOYEES e
on c.SALESREPEMPLOYEENUMBER = e.EMPLOYEENUMBER
left join sys.orders o
on c.CUSTOMER NUMBER = o.CUSTOMERNUMBER
left join sys.orderdetails od
on o.ORDERNUMBER = od.ORDERNUMBER
left join sys.products p
on od.PRODUCTCODE = p.PRODUCTCODE
left join sys.PAYMENTS py
on c.CUSTOMERNUMBER = py.customernumber
I am a newbie with SQL and databases, so any help is appreciated.
Here are some observations on things going wrong:
You have curly braces that are not necessary (perhaps this is a typo in the question).
You are selecting *, but have duplicate column names (such as productcode), which prevents the view from being created. Best practice: list all the columns explicitly in the view.
You have c.CUSTOMER NUMBER = o.CUSTOMERNUMBER. The space is probably a typo. If not, change the name so the space is not part of the name. Best practice: Use identifiers that do not have to be escaped.
I am not aware of a sys.customers table. The sys schema should only be used for internal Oracle objects. (Here is one source.)
thank you for all the inputs. they helped me a lot in figuring out the answer.
Following is the query for the question asked above.it gave me a view with columns from all tables.
create or replace view overall AS
select c.*,
e.LASTNAME,
e.FIRSTNAME,
e.EXTENSION,
e.EMAIL,
e.OFFICECODE,
e.REPORTSTO,
e.JOBTITLE,
o.ORDERNUMBER,
o.ORDERDATE,
o.REQUIREDDATE,
o.SHIPPEDDATE,
o.STATUS,
o.COMMENTS,
od.PRODUCTCODE,
od.QUANTITYORDERED,
od.PRICEEACH,
od.ORDERLINENUMBER,
p.PRODUCTNAME,
p.PRODUCTLINE,
p.PRODUCTSCALE,
p.PRODUCTVENDOR,
p.PRODUCTDESCRIPTION,
p.QUANTITYINSTOCK,
p.BUYPRICE,
p.MSRP,
py.CHECKNUMBER,
py.PAYMENTDATE,
py.AMOUNT
from sys.customers c
left JOIN EMPLOYEES e
on c.SALESREPEMPLOYEENUMBER = e.EMPLOYEENUMBER
left join sys.orders o
on c.CUSTOMERNUMBER = o.CUSTOMERNUMBER
left join sys.orderdetails od
on o.ORDERNUMBER = od.ORDERNUMBER
left join sys.products p
on od.PRODUCTCODE = p.PRODUCTCODE
left join sys.PAYMENTS py
on c.CUSTOMERNUMBER = py.customernumber
;
Your query looks alright, but I don't think it will let you create a view if more than one column has the same name.
Since there are duplicates, e.g. CITY, I think the only way around it is to name all the columns and give unique names for duplicate columns.
I'm taking my first steps in terms of practical SQL use in real life.
I have a few tables with contractual and financial information and the query works exactly as I need - to a certain point. It looks more or less like that:
SELECT /some columns/ from CONTRACTS
Linked 3 extra tables with INNER JOIN to add things like department names, product information etc. This all works but they all have simplish one-to-one relationship (one contract related to single department in Department table, one product information entry in the corresponding table etc).
Now this is my challenge:
I also need to add contract invoicing information doing something like:
inner join INVOICES on CONTRACTS.contnoC = INVOICES.contnoI
(and selecting also the Invoice number linked to the Contract number, although that's partly optional)
The problem I'm facing is that unlike with other tables where there's always one-to-one relationship when joining tables, INVOICES table can have multiple (or none at all) entries that correspond to a single contract no. The result is that I will get multiple query results for a single contract no (with different invoice numbers presented), needlessly crowding the query results.
Essentially I'm looking to add INVOICES table to a query to just identify if the contract no is present in the INVOICES table (contract has been invoiced or not). Invoice number itself could be presented (it is with INNER JOIN), however it's not critical as long it's somehow marked. Invoice number fields remains blank in the result with the INNER JOIN function, which is also necessary (i.e. to have the row presented even if the match is not found in INVOICES table).
SELECT DISTINCT would look to do what I need, but I seemed to face the problem that I need to levy DISTINCT criteria only for column representing contract numbers, NOT any other column (there can be same values presented, but all those should be presented).
Unfortunately I'm not totally aware of what database system I am using.
Seems like the question is still getting some attention and in an effort to provide some explanation here are a few techniques.
If you just want any contract with details from the 1 to 1 tables you can do it similarily to what you have described. the key being NOT to include any column from Invoices table in the column list.
SELECT
DISTINCT Contract, Department, ProductId .....(nothing from Invoices Table!!!)
FROM
Contracts c
INNER JOIN Departments D
ON c.departmentId = d.Department
INNER JOIN Product p
ON c.ProductId = p.ProductId
INNER JOIN Invoices i
ON c.contnoC = i.contnoI
Perhaps a Little cleaner would be to use IN or EXISTS like so:
SELECT
Contract, Department, ProductId .....(nothing from Invoices Table!!!)
FROM
Contracts c
INNER JOIN Departments D
ON c.departmentId = d.Department
INNER JOIN Product p
ON c.ProductId = p.ProductId
WHERE
EXISTS (SELECT 1 FROM Invoices i WHERE i.contnoI = c.contnoC )
SELECT
Contract, Department, ProductId .....(nothing from Invoices Table!!!)
FROM
Contracts c
INNER JOIN Departments D
ON c.departmentId = d.Department
INNER JOIN Product p
ON c.ProductId = p.ProductId
WHERE
contnoC IN (SELECT contnoI FROM Invoices)
Don't use IN if the SELECT ... list can return a NULL!!!
If you Actually want all of the contracts and just know if a contract has been invoiced you can use aggregation and a case expression:
SELECT
Contract, Department, ProductId, CASE WHEN COUNT(i.contnoI) = 0 THEN 0 ELSE 1 END as Invoiced
FROM
Contracts c
INNER JOIN Departments D
ON c.departmentId = d.Department
INNER JOIN Product p
ON c.ProductId = p.ProductId
LEFT JOIN Invoices i
ON c.contnoC = i.contnoI
GROUP BY
Contract, Department, ProductId
Then if you actually want to return details about a particular invoice you can use a technique similar to that of cybercentic87 if your RDBMS supports or you could use a calculated column with TOP or LIMIT depending on your system.
SELECT
Contract, Department, ProductId, (SELECT TOP 1 InvoiceNo FROM invoices i WHERE c.contnoC = i.contnoI ORDER BY CreateDate DESC) as LastestInvoiceNo
FROM
Contracts c
INNER JOIN Departments D
ON c.departmentId = d.Department
INNER JOIN Product p
ON c.ProductId = p.ProductId
GROUP BY
Contract, Department, ProductId
I would do it this way:
with mainquery as(
<<here goes you main query>>
),
invoices_rn as(
select *,
ROW_NUMBER() OVER (PARTITION BY contnoI order by
<<some column to decide which invoice you want to take eg. date>>) as rn
)
invoices as (
select * from invoices_rn where rn = 1
)
select * from mainquery
left join invoices i on contnoC = i.contnoI
This gives you an ability to get all of the invoice details to your query, also it gives you full control of which invoice you want see in your main query. Please read more about CTEs; they are pretty handy and much easier to understand / read than nested selects.
I still don't know what database you are using. If ROW_NUMBER is not available, I will figure out something else :)
Also with a left join you should use COALESCE function for example:
COALESCE(i.invoice_number,'0')
Of course this gives you some more possibilities, you could for example in your main select do:
CASE WHEN i.invoicenumber is null then 'NOT INVOICED'
else 'INVOICED'
END as isInvoiced
You can use
SELECT ..., invoiced = 'YES' ... where exists ...
union
SELECT ..., invoiced = 'NO' ... where not exists ...
or you can use a column like "invoiced" with a subquery into invoices to set it's value depending on whether you get a hit or not
Im practicing basic SQL with this site http://www.sqlishard.com/Exercise
Here is the question:
S5.0 - INNER JOIN
Now that we can pull data out of a single table and qualify column
names, let's take it a step further. JOIN statements allow us to
'join' the rows of several tables together using a condition to define
how they match one another. SELECT [columns] FROM FirstTable INNER
JOIN SecondTable ON FirstTable.Id = SecondTable.FirstTableId
Try using the INNER JOIN syntax to SELECT all columns from the
Customers and Orders tables where the CustomerId column in Orders
matches the Id column in Customers. Since both tables have an Id
column, you will need to qualify the Customers id in the WHERE clause
with either the table name or a table alias.
Here is my answer:
SELECT *
FROM Customers AS c
INNER JOIN Orders AS o ON c.ID = o.ID
WHERE o.CustomerID = c.ID
The site says im wrong? Could anyone explain where i'm going wrong?
EDIT: I see now I dont need the WHERE clause, but the question states..
you will need to qualify the Customers id in the WHERE clause with
either the table name or a table alias.
Hence my confusion. Thanks none the less.
Try this way:
SELECT c.ID,o.ID
FROM Customers AS c
INNER JOIN Orders AS o ON o.CustomerID = c.ID
or using where clause
SELECT *
FROM Customers AS c, Orders AS o
where o.CustomerID = c.ID
If you use JOIN.. ON, you do not need where clause
Suppose I have 3 tables.
Sales Rep
Rep Code
First Name
Last Name
Phone
Email
Sales Team
Orders
Order Number
Rep Code
Customer Number
Order Date
Order Status
Customer
Customer Number
Name
Address
Phone Number
I want to get a detailed report of Sales for 2010. I would be doing a join. I am interested in knowing which of the following is more efficient and why ?
SELECT
O.OrderNum, R.Name, C.Name
FROM
Order O INNER JOIN Rep R ON O.RepCode = R.RepCode
INNER JOIN Customer C ON O.CustomerNumber = C.CustomerNumber
WHERE
O.OrderDate >= '01/01/2010'
OR
SELECT
O.OrderNum, R.Name, C.Name
FROM
Order O INNER JOIN Rep R ON (O.RepCode = R.RepCode AND O.OrderDate >= '01/01/2010')
INNER JOIN Customer C ON O.CustomerNumber = C.CustomerNumber
JOINs must reflect the relationship aspect of your tables. WHERE clause, is a place where you filter records. I prefer the first one.
Make it readable first, table relationships should be obvious (by using JOINs), then profile
Efficiency-wise, the only way to know is to profile it, different database have different planner on executing the query
Wherein some database might apply filter first, then do the join subsquently; some database might join tables blindly first, then execute where clause later. Try to profile, on Postgres and MySQL use EXPLAIN SELECT ..., in SQL Server use Ctrl+K, with SQL Server you can see which of the two queries is faster relative to each other