Sql left outer join with three tables
I am developing basically an e-commerce application. Application has two pages (all product and my-basket) authenticated user can add product to own basket. and I have three tables, the tables contains following data. I want to if the user adds product to own basket, these products don't exist on this user's all product page.
How should be the SQL query? I am looking query for all product page. so query's return type must be Product.
If user added any products to own basket on all product page these products shouldn't see on the all product page for this user.
PRODUCT TABLE +-------+--------+ | id | name | +-------+--------+ | 1 | p1 | | 2 | p2 | +-------+--------+ USER TABLE +-------+--------+ | id | name | +-------+--------+ | 3 | U1 | | 4 | U2 | +-------+--------+ BASKET TABLE +-------+---------+-------------+ | id | fk_user | fk_product | +-------+---------+-------------+ | 5 | 3 | 1 | | 6 | 4 | 2 | +-------+---------+-------------+
So if authenticated user's id is 3. The user should see p2 product on own all product page.
SELECT product.name FROM product LEFT JOIN basket ON basket.fk_product = product.id WHERE (basket.fk_user != 3 OR basket.fk_user IS NULL)
Check my demo query
If you want you can also join the
user table but with the data you gave me is not necessary.
left join keeps all rows in the first (product) table plus all rows in the second (basket) table, when the on clause evaluates to
When the on clause evaluates to
left join still keeps all rows in the first table with
NULL values for the second table.
SQL Server LEFT JOIN By Practical Examples, Introduction to SQL Server LEFT JOIN clause The LEFT JOIN clause allows you to query data from multiple tables. It returns all rows from the left table and the matching rows from the right table. If no matching rows found in the right table, NULL are used. The outer join can be 2 types: left join and right join. This is an example of three table left join: SELECT s.name AS student_name, c.name AS course_name FROM student s LEFT JOIN student_course sc ON s.id = sc.student_id LEFT JOIN course c ON sc.course_id = c.id;
or, more commonly...
SELECT p.name FROM product p LEFT JOIN basket b on b.fk_product = p.id AND b.fk_user = 3 WHERE b.fk_user is null
SQL Left Join, Left Join: Syntax SELECT * FROM table1 LEFT [ OUTER ] JOIN table2 ON Example of SQL Left Join using multiple tables. To filtered out� There are two types of outer join in SQL : 1.Left outer Join . 2.Right outer Join. Left outer Join : Left outer join in SQL is nothing but fetching the common records from two or more tables and all records from Left table. Syntax : Type 1:Left Outer Join Syntax with + Select t1.col1,t2.col2….t ‘n’col ‘n.’. from table1 t1,table2 t2
What you are describing sounds like
SELECT p.name FROM product p WHERE NOT EXISTS (SELECT 1 FROM basket b WHERE b.fk_product = f.id AND b.fk_user = 3 );
This seems like the most direct interpretation of your question.
How to Use Outer Joins to Combine Data from Three Tables in MySQL, Another Example for Outer Joins (three tables). In this tutorial, we continue left and right join study with an example of three tables joined. The three tables The purpose is to show you the different styles of writing SQL scripts. Personally I � The SQL LEFT OUTER JOIN is the types of the outer join to combine the two tables. It combines the two table but prefer the rows of the first table and add all the rows from the first table to the resulted table. To get the left join output using SQL, it finds all the rows from the first table including the matching rows from the right table.
How to LEFT JOIN Multiple Tables in SQL, An SQL JOIN clause links the data from two or more database tables. Let's find out what is the OUTER JOIN and how does it work! Read more. SQL left outer join is also known as SQL left join. Suppose, we want to join two tables: A and B. SQL left outer join returns all rows in the left table (A) and all the matching rows found in the right table (B). It means the result of the SQL left join always contains the rows in the left table. The following illustrate SQL left outer syntax
Need SQL outer join help with 3 tables, First, join TABLE_2 and TABLE_3 using an inner join and additionally filtering on Value_A = 'a' : SELECT t2.ID_1, t3.ID_A, t3.Value_A FROM� In short, the LEFT JOIN clause returns all rows from the left table (T1) and matching rows or NULL values from the right table (T2). The following illustrates the LEFT JOIN of two tables T1 (1, 2, 3) and T2 (A, B, C). The LEFT JOIN will match rows from the T1 table with the rows from T2 table using patterns:
SQL JOIN, JOIN Syntax, JOIN Differences, 3 tables, FULL (OUTER) JOIN: Selects all records that match either left or right table records. LEFT (OUTER) JOIN: Select records from the first (left-most) table with matching right table records. RIGHT (OUTER) JOIN: Select records from the second (right-most) table with matching left table records. Two approaches to join three or more tables: 1. Using joins in sql to join the table: The same logic is applied which is done to join 2 tables i.e. minimum number of join statements to join n tables are (n-1). Query: