I'm new in SQL language and RDBMS. I'm trying to show the same column from the same table but using different references.
Problem
I have the following database and tables:
DATABASE: PRODUCTS
PROD (CodProd <PK>, Descr, PrecoUnit, QtdeEst)
PROD_SIM (CodProd <PK>, CodProdSim <PK>)
PROD_SIM (CodProd) REFERENCES PROD (CodProd)
PROD_SIM (CodProdSim) REFERENCES PROD (CodProd)
I was asked to show all the products desc that have other products considered similar to them, and show the desc column from the similar product too.
Example
I have the following data:
PROD:
(0, `spachetti`, 12.5, 2)
(1, `noodle`, 8.0, 4)
PROD_SIM:
(0, 1)
I want to show this:
+-----------+-------------+
| Product | SimilarProd |
+-----------+-------------+
| spaghetti | noodle |
+-----------+-------------+
Tried
SELECT PROD.Desc, PROD.Desc FROM PROD
INNER JOIN PROD_SIM ON PROD_SIM.CodProd = PROD.CodProd
But of course, this will not work, because I'm selecting the same table twice and I don't know how to specify from what reference should the selected column consider display Desc.
If I've understood your request and your schema correctly (I don't have enough reputation to comment), I think you're only one join away from achieving the desired result:
SELECT A.Desc original_product, B.Desc similar_product
FROM PROD A
INNER JOIN PROD_SIM S ON A.CodProd = S.CodProd
INNER JOIN PROD B ON S.CodProdSim = B.CodProd
Related
I am new in Sql. My question is how to get data from three different tables with null values.
I have tried a query as below:
SELECT *
FROM [USER]
JOIN [Location] ON ([Location].UserId = [USER].Id)
JOIN [ParentChild] ON ([ParentChild].UserId = [USER].Id) WHERE ParentId=7
which I find from this link.
Its working fine but, it not fetches all and each data associated with the ParentId
Something like it only fetches data which are available in all tables, but also omits some data which not available in Location tables but it comes under the given ParentId.
For example:
+----------+-------------+
| UserId | ParentId |
+----------+-------------+
| 1 | 7 |
+----------+-------------+
| 8 | 7 |
+----------+-------------+
For userId 8, there is data available in Location table,so it fetches all data. But there is no data for userId 1 available in Location table, so the query didn't work for this.
But I want all and every data.
If there is no data for userId then it can return only null columns.
Is it possible ??
hope everyone can understand my problem.
If you always want to return a list of users, but some may not have locations then you want to change the type of join from an "Inner Join" (or as you have used the short hand "JOIN") to a "Left Join".
SELECT *
FROM [USER]
INNER JOIN [ParentChild] ON ([ParentChild].UserId = [USER].Id)
LEFT JOIN [Location] ON ([Location].UserId = [USER].Id)
WHERE ParentId=7
This doesn't account for users that do not have a parent. If you still want to return users who do not have a parent then you would then need to change the JOIN type to your ParentChild table to a LEFT join also.
Hello all :) I'm wondering if there is way to tell the database to look at the schema and infer the JOIN predicate:
+--------------+ +---------------+
| prices | | products |
+--------------+ +---------------+
| price_id (PK)| |-1| product_id(PK)|
| prod_id |*-| | weight |
| shop | +---------------+
| unit_price |
| qty |
+--------------+
Is there a way (preferably in Oracle 10g) to go from:
SELECT * FROM prices JOIN product ON prices.prod_id = products.product_id
to:
SELECT * FROM pricesIMPLICIT JOINproduct
The closest you can get to not writing the actual join condition is a natural join.
select * from t1 natural join t2
Oracle will look for columns with identical names and join by them (this is not true in your case). See the documentation on the SELECT statement:
A natural join is based on all columns in the two tables that have the same name. It selects rows from the two tables that have equal values in the relevant columns. If two columns with the same name do not have compatible data types, then an error is raised
This is very poor practice and I strongly recommend not using it on any environment
You shouldnt do that. Some db systems allow you to but what if you modify the fk's (i.e. add foreign keys)? You should always state what to join on to avoid problems. Most db systems won't even allow you to do an implicit join though (good!).
Sorry if this is a basic question. I'm fairly new to SQL, so I guess I'm just missing the name of the concept to search for.
Quick overview.
First table (items):
ID | name
-------------
1 | abc
2 | def
3 | ghi
4 | jkl
Second table (pairs):
ID | FirstMember | SecondMember Virtual column (pair name)
-------------------------------------
1 | 2 | 3 defghi
2 | 1 | 4 abcjkl
I'm trying to build the virtual column shown in the second table
It could be built at the time any entry is made in the second table, but if done that way, the data in that column would get wrong any time one of the items in the first table is renamed.
I also understand that I can build that column any time I need it (in either plain requests or stored procedures), but that would lead to code duplication, since the second table can be involved in multiple different requests.
So is there a way to define a "virtual" column, that could be accessed as a normal column, but whose content is built dynamically?
Thanks.
Edit: this is on MsSql 2008, but an engine-agnostic solution would be preferred.
Edit: the example above was oversimplified in multiple ways - the major one being that the virtual column content isn't a straight concatenation of both names, but something more complex, depending on the content of columns I didn't described. Still, you've provided multiple paths that seems promising - I'll be back. Thanks.
You need to join the items table twice:
select p.id,
p.firstMember,
p.secondMember,
i1.name||i2.name as pair_name
from pairs as p
join items as i1 on p.FirstMember = i1.id
join items as i2 on p.SecondMember = i2.id;
Then put this into a view and you have your "virtual column". You would simply query the view instead of the actual pairs table wherever you need the pair_name column.
Note that the above uses inner joins, if your "FirstMember" and "SecondMember" columns might be null, you probably want to use an outer join instead.
You can use a view, which creates a table-like object from a query result, such as the one with a_horse_with_no_name provided.
CREATE VIEW pair_names AS
SELECT p.id,
p.firstMember,
p.secondMember,
CONCAT(i1.name, i2.name) AS pair_name
FROM pairs AS p
JOIN items AS i1 ON p.FirstMember = i1.id
JOIN items AS i2 ON p.SecondMember = i2.id;
Then to query the results just do:
SELECT id, pair_name FROM pair_names;
You could create a view for your 'virtual column', if you wanted to, like so:
CREATE VIEW aView AS
SELECT
p.ID,
p.FirstMember,
p.SecondMember,
a.name + b.name as 'PairName'
FROM
pairs p
LEFT JOIN
items a
ON
p.FirstMember = a.ID
LEFT JOIN
items b
ON
p.SecondMember = b.ID
Edit:
Or, of course, you could just use a similar select statement every time.
When selecting from tables you can name the results of a column using AS.
SELECT st.ID, st.FirstMember, st.SecondMember, ft1.Name + ft2.Name AS PairName
FROM Second_Table st
JOIN First_Table ft1 ON st.FirstMember = ft1.ID
JOIN First_Table ft2 ON st.SecondMember = ft2.ID
Should give you something like what you are after.
Edit: this isn't to be a dynamic output, the output view structure is fixed.
I am trying to create a SQL Server view that shows a single fixed column row for each user, and flattens out an associated one to many table into that row.
Although the associated table has a one to many relationship, the output table structure is limited to 4 elememts form that table.
My table structure is like so:
User (Id, FirstName, LastName)
Assessment (Id, Date, Location, User_Id)
Topics (Id, Topic, Assessment_Id)
Where the Assessment is joined to the User by the User_Id (One 2 One), and the Topics are joined to the Assessment by the Assessment_Id.
So, if I have three topics for an assessment, I'd want the view to look something like:
User_Id | FirstName | LastName | Date | Location | Topic1 | Topic2 | Topic3 | Topic4 |
1 | dave | toby | 2/2/11 | In situ | apples | pears | lemons | NULL |
My current SQL looks like this:
SELECT User.Id, User.FirstName, User.LastName, Assessment.Date, Assessment.Location, Topic.Topic
FROM User LEFT OUTER JOIN
Assessment INNER JOIN
Topic ON Assessment.Id = Topic.Assessment_Id ON
User.Id = Assessment.User_Id
But this returns a row for each concern - it doesn't compress them to one line. I've played with a few different joins, but haven't been able to get the behaviour I want.
Is it possible to do this in a view?
What do I need to do to make it happen??
Thanks!
There is no such JOIN. SQL has a fixed column output: so you can't add arbritrary numbers of columns. It doesn't matter if it's a view, direct or in a stored procedure.
There are 2 main options
concatenate the many rows into one column which is a popular questions here on SO. One random solution using XML PATH
use dynamic SQL to add a column per row in a stored procedure.
Note: PIVOT is fixed column output too
Edit: for a maximum of 4 child rows
SELECT
P.col1, P.col2,
C1.col1 AS Topic1,
C2.col1 AS Topic2,
C3.col1 AS Topic2,
C4.col1 AS Topic4
FROM
Parent P
LEFT JOIN
Child C1 ON P.Key = C1.FKey AND C1.ID = 1
LEFT JOIN
Child C2 ON P.Key = C2.FKey AND C2.ID = 2
LEFT JOIN
Child C3 ON P.Key = C3.FKey AND C3.ID = 3
LEFT JOIN
Child C4 ON P.Key = C4.FKey AND C4.ID = 4
You can use PIVOT too but I prefer the simpler self joins.
Take a look at PIVOT table functionality - e.g. http://www.help-sql.info/27/9/610208.html and http://blog.sqlauthority.com/2008/05/22/sql-server-pivot-table-example/
Although you will need to know the AssessmentId's before you can write the PIVOT
I need to localize a SQL Server 2008 database. After investigating recommendations, I have found that it is best to have separate tables or each of the languages for the strings. That way different sorting settings can be set for each table. For example, a typical Product table has ProdID, Product Description, and Price fields. The recommended solution is to set the table structures to have the Product table be ProdID and Price. Then a specific table for each language would have the following structure: ProdID and Description.
My question is how do I create a store procedure that has a parameter which passes in the culture to use for the sub-table and then use that to join the tables? The sub-table needs to change based on the parameter. How can that be done? I am using SQL Server 2008.
First off, are you sure you really want to implement different tables for each culture? It would make more sense to modify your Product table to remove the description, and then add a ProductDescription table with a ProdID, culture, and description field. This way you don't have to toy around with dynamic SQL (which is what you'll have to use) to select the correct table based on the culture parameter.
...specific table for each language would have the following structure: ProdID and Description.
...which is why you're having to look at a really involved setup to get your information out of the database.
A better approach would be to use a single table, and use a code for the language. You don't want to be defining a column per attribute you want translated either, so you'd be looking at implementing something like:
LANGUAGES table
LANGUAGE_ID, pk
LANGUAGE_DESCRIPTION
Example data:
LANGUAGE_ID | LANGUAGE_DESCRIPTION
------------------------------------
1 | ENGLISH
2 | FRENCH
TRANSLATED_ATTRIBUTES table
TRANSLATED_ATTRIBUTE_ID, pk
TRANSLATED_ATTRIBUTE_DESC
Example data:
TRANSLATED_ATTRIBUTE_ID | TRANSLATED_ATTRIBUTE_DESC
------------------------------------
1 | PROD_ID
2 | PROD_DESC
LOCALIZATIONS table
LANGUAGE_ID, pk
TRANSLATED_ATTRIBUTE_ID, pk
TRANSLATED_VALUE
Example data:
LANGUAGE_ID | TRANSLATED_ATTRIBUTE_ID | TRANSLATED_VALUE
----------------------------------------------------------
1 | 1 | Product ID
2 | 1 | Produit ID
You'll want a table associating the TRANSLATED_ATTRIBUTE_ID with a given item - Product is the example you've given so:
ATTRIBUTES table
ATTRIBUTE_ID, pk
ATTRIBUTE_TYPE_CODE, fk
TRANSLATED_ATTRIBUTE_ID, fk
Example data:
ATTRIBUTE_ID | ATTRIBUTE_TYPE_CODE | TRANSLATED_ATTRIBUTE_ID
----------------------------------------------------------------
1 | PRODUCT | 1
If you want to relate on a per product basis:
ATTRIBUTES table
ATTRIBUTE_ID, pk
PRODUCT_ID, fk
TRANSLATED_ATTRIBUTE_ID, fk
Now can you use two parameters - the language (English) & what the item is (Product):
SELECT t.translated_attribute_desc,
t.translated_value
FROM LOCALIZATIONS t
JOIN TRANSLATED_ATTRIBUTES ta ON ta.translated_attribute_id = t.translated_attribute_id
JOIN ATTRIBUTES a ON a.translated_attribute_id = ta.translated_attribute_id
JOIN ATTRIBUTE_TYPE_CODES atc ON atc.attribute_type_code = a.attribute_type_code
JOIN LANGUAGES lang ON lang.language_id = t.language_id
WHERE lang.language_description = 'ENGLISH' --alternate: lang.language_id = 1
AND atc.attribute_type_code = 'PRODUCT'
You can pivot the data as necessary.