my table contains category_name and parent_category_Id column
My parent_category data contains, the same table primary key id.
i need to select the all rows and insted my parent_category_Id i need to select the catogry_name
I think this is what you're after, though it's hard to discern from the question:
Select c.*
From category c
Join parent_category pc ON c.parent_category_id = pc.id
Where pc.category_name = 'Some Name'
Try something like:
SELECT c.category_name, p.category_name
FROM categories c LEFT JOIN parent_categories p
ON c.parent_id = p.id
PS: you may think about restructuring your database, it would make more sense to store all the categories in the same table. See for instance: http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/
You should restructure your database to have one table with:
id, name, and parent columns, with the parent column referencing the same table's id column. Your current database is not normalized and will likely cause issues in the future.
At a minimum you should have an auto_increment id column in the categories table.
The other answers here are correct (depending on the SQL server you are using).
Related
I have a table A with ID's only and another table B with two columns, ID and Product Number. The ID column in table B has nulls and Product Number has Product Numbers. I would like to update table B with the ID's in column in no specific order just so that the Product Number has ID's.
I have tried to use update but that has not worked, have tried insert but it just adds the ID's in A to the bottom of the list in B. Would like to do this in Microsoft SQL.
SQL code tried:
IF OBJECT_ID('tempdb..#ProductNum') IS NOT NULL DROP TABLE #ProductNum
SELECT ID
INTO #ProductNum
FROM Products
UPDATE [ProductCatalogue] PC
SET
PC.ID = Pn.ID
FROM #ProductNum Pn
INNER JOIN
[ProductCatalogue] PC
ON Pc.ID = Pn.ID
WHERE Pc.ID IS NULL
It sounds a lot like you would be better off having the ID-Column Autoincrement, instead of giving it the IDs from table A. This is already explained in this answer.
In case you actually need the specific IDs from table A, this SO thread might help you.
Solved the issue by creating auto increment columns on each table and called it Row_ID. Then I used Row_ID to join the tables together with some logic provided by #Chris above.
I am trying to join two tables together using UNION (although im not sure that is the best option) there are technically two related columns however they don't have the same name so i'm assuming that isn't an option here is my query:
SELECT title, type, release_date FROM pictures
UNION
SELECT name, residence, NULL as Col3 FROM actor
ORDER BY release_date ASC;
It is only printing out the pictures columns from this? Thank you for any help in advance.
To relate two tables you could use some foreign key or a third table in the case of beign a many-to-many relation, you should use one of the join options, for example:
Imagine that exists a table that relate actor and pictures, called actor_pictures.
Image that we will relate the tables by id (it could be another one, and it doesn't have to have the same name).
You could do this:
SELECT * FROM actor_pictures ap
JOIN actor a ON ap.actor_id = a.id
JOIN pictures p ON ap.pictures_id = p.id
ORDER BY p.release_date ASC
Read this: https://www.w3schools.com/sql/sql_join.asp
I've just started learning SQL and need help with an assignment question. I am asked to look through a dataset about Kickstarter campaigns. I'm asked to find the top 3 categories by amount of backers.
Here is the ER diagram:
ER diagram
In the 'Campaign' Table, there's the 'backers' column, but the 'Category' Table is only related with the Campaign through the 'Sub-Category' Table.
So far, I have been able to Join sub_category.category_id with the sub-category.category_name, but i'm not sure how to take this new Table and join it with Campaign
SELECT C.name AS category_name, SC.category_id, SC.id AS SC_id
FROM Category AS C
JOIN sub_category AS SC ON C.id = SC.category_id
Screenshot
I am hoping to have a table where there is a column for 'Category Name' and 'Backers' and then simply sort it by the number of backers
How should I go about this? Am I on the right track?
SELECT C.name AS category_name, CA.backers
FROM campaign AS CA
JOIN sub_category AS SC
ON CA.sub_category_id =SC.Id
JOIN Category AS C
ON C.id = SC.category_id
order by CA.backers
You can have multiple joins all together in one query.
Secondly there is a connection between Campaign and Sub_Category table which will help to join these two tables.
Later we can then join Category table as these two table has a connection between them based on Category_Id which is a foreign key in sub category table.
At last you can just order by based on Backers.
Let me know if you have any issue or doubt in comments.
And just to take Magnus's answer and rewrite visually, you can better see the hierarchy of the query. See how it closely resembles that of your table relationships
SELECT
C.name category_name,
CA.backers
FROM
campaign CA
JOIN sub_category SC
ON CA.sub_category_id = SC.Id
JOIN Category C
ON SC.category_id = C.id
order by
CA.backers
Notice the indentation to the table its ID is based upon from that prior to it. This way you know which column FROM connecting TO. I have found that if you list the tables in the FROM clause first to show all the HOW tables are related and ON what foreign : primary key relationships, that is the hardest part. Then its just pulling the columns you want after that.
So I have three tables: companies, addresses and company_address.
For optimization reasons I need to copy city column from addresses table to companies table. Relation between companies and addresses is many to one (as many companies can occupy same address). They are connected through company_address table, consisting of address_id and company_id columns.
I found this solution for case without intermediate table: How to copy one column of a table into another table's column in PostgreSQL comparing same ID
Trying to modify query I came up with:
UPDATE company SET company.city=foo.city
FROM (
SELECT company_address.company_id, company_address.address_id, address.city
FROM address LEFT JOIN company_address
ON address.id=company_address.address_id
) foo
WHERE company.id=foo.company_id;
but it gives error:
ERROR: column "company" of relation "company" does not exist
I cant figure out what is going on. I'll be grateful for any ideas.
You don't need a subquery for that. Also, refer in the SET clause to your table columns without preceding with table name.
I believe that since your WHERE condition includes joined table, it should be INNER JOIN instead of a LEFT JOIN.
UPDATE company c
SET city = a.city
FROM address a
INNER JOIN company_address ca ON a.id = ca.address_id
WHERE c.id = ca.company_id
Note how using aliases for table names shortens the code and makes it readable at the very first glance.
You're right syntactically, you just don't need the table name at the beginning of the update statement:
UPDATE company SET city=foo.city
FROM (
SELECT company_address.company_id, company_address.address_id, address.city
FROM address LEFT JOIN company_address
ON address.id=company_address.address_id
) foo
WHERE company.id=foo.company_id;
I have 2 tables. One who is like a transactional table
userId category
Second table also has
userId (as primary key)
and other columns (not important)
I wanted to create a view based on these 2 tables. Also, I want to have one column which puts into the cells the count from the transactional table who has the same id and eventually matches a special categorie f.e "car".
I thought of maybe using nested select statement, but since i'm a beginner i'm a little bit confused.
Try something like this.
select count(b.userId) as ID, b.category from table2 a inner join transactional b
on a.userId = b.userId where b.category= 'car' group by b.category;