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I have a simple database with few tables (and some sample columns):
Posts (ID, Title, Content)
Categories (ID, Title)
PostCategories (ID, ID_Post, ID_Category)
Is there a way to create single SQL query which will return posts with categories that are assigned to each post?
You can use the GROUP_CONCAT function
select p.*, group_concat(DISTINCT c.title ORDER BY c.title DESC SEPARATOR ', ') from Posts p inner join PostCategories pc on p.ID = pc.ID_Post inner join Categories c on pc.ID_Category = c.ID group by p.id, p.title, p.content
How to Handle a Many-to-Many Relationship in Database Design , Learn how to handle many-to-many relationships in database design with an [ NEW TREND REPORT] The Database Evolution: SQL or NoSQL in the Age of Big Data because this only stores a single relationship, and we need many. multiple values, which is very hard for maintenance and querying. The One-to-Many relationship is defined as a relationship between two tables where a row from one table can have multiple matching rows in another table. This relationship can be created using Primary key-Foreign key relationship. In the One-to-Many Relationship in SQL Server, for example, a book can have multiple authors.
Simple joins work well.
SELECT posts.id, posts.title, categories.id, categories.title FROM posts JOIN posts_categories ON posts.id = posts_categories.post_id JOIN categories ON posts_categories.category_id = categories.id
Need explanation SELECT query on many to many relationship , Your version uses a very old JOIN syntax from the ANSI-89 standards - as in 1989. In 1992, the standard was updated to adopt the JOIN. Many-to-many: Multiple records in one table are related to multiple records in another table. Handling a one-to-one relationship or a one-or-many relationship can be done by adding the primary
select p.*, c.* from Posts p inner join PostCategories pc on p.ID = pc.ID_Post inner join Categories c on pc.ID_Category = c.ID
If you mean with only one record per post, I will need to know what database platform you are using.
How to Manage Many-to-Many Joins in SQL for HTML5and CSS3 , Inner joins are a perfect way to implement one-to-many SQL relationships for The point of this query is to use the hero_power table to identify relationships� I have just created a many to many relationship in MS Access with three tables as shown below AE Career Fair - Struc contains a list of companies where the company name is distinct. Office Locations - Int is a junction table containing in one column all the companies occuring in AE Career Fair - Struc, but duplicated based on the countries in
Sure. If I understand your question correctly, it should be as simple as
SELECT Posts.title, Categories.title FROM Posts, Categories, PostCategories WHERE PostCategories.ID_Post = Posts.ID AND PostCategories.ID_Category = Categories.ID ORDER BY Posts.title, Categories.title;
Getting one row per Post will be a little more complicated, and will depend on what RDBMS you're using.
Many-to-many relationships, Relational database systems usually don't allow you to implement a direct many- to-many relationship between two tables. Consider the example of keeping track � SQL Query to get data from two table with one to many relationship [Answered] RSS 9 replies Last post Jul 04, 2011 07:37 AM by NidaNovice
We can use this query also.
select e.*,c.* from Posts e, Categories c, PostCategories cp where cp.id in ( select s.id from PostCategories s where s.empid=e.id and s.companyid=c.id );
How to create a many-to-many relationship, Create a third table: right-click the database diagram body and select New Table Add new table to create many-to-many relationship SQL� SQL queries asking for the combined relationship tables from both databases View in datagrid all data from master table where relationship with other table in ms access using in VB.NET sql problem (query and relationship)
Creating multiple tables and table relationships, Such relationships include: One-to-One, One-to-Many, and Many-to-Many. Thus far in this book, all the work we've done has been with a single database table. Executing the above SQL statement will create an addresses table, and� Hi all, I have two tables with one to many relationship. Can i get the line table data separated by comma within a single select statement in sql 2005.
Inner vs Outer Joins on a Many-To-Many Relationship, Inner vs Outer Joins on a Many-To-Many Relationship my examples, then here's the zipped mysqldump file: recipes-db.sql. Since there are multiple tables in the query now, it is important to If you were looking for examples of inner and outer joins across a real (if simple!) database with multiple joins,� How can I modify the query to return something like this: AppID AppName AppType Tags 1 Application1 Utility Test1,Test2,Test3 sql-server-2008 join syntax group-concatenation
Define a Many-to-Many Relationship and Many-to , SQL Server Analysis Services no A simple many-to-many relationship includes two dimensions having a many-to-many To simplify your model, clear all the measures, and then select just Sales Amount and Fact Internet� Many to Many Relationships In some cases, you may need multiple instances on both sides of the relationship. For example, each order can contain multiple items. And each item can also be in multiple orders.
- Thx for answers. I'm using MySQL. To be clear what I mean is that if there are 3 records in Categories, 1 record in Posts and 3 records in PostCategories (so that one post belongs to three categories), then the query should return only one row containing the post, but for example in one of its columns will be those categories where it belongs. In OOP it will be something like one instance of post object containing properties for ID, Title, Content and (generic) list of categories.
- Note that this will work with current versions of mysql, but not necessarily with other database systems.