Therefore, they’re used in the payment table as a foreign key. A JOIN is a means for combining fields from two tables by using values common to each. Note that the student_id and course_code columns form a primary key in the enrollment table. SQLite Joins clause is used to combine records from two or more tables in a database. In the next condition, we get the course_code column from the enrollment table and course_code from the payment table. In the first part, we use the student_id column from the enrollment table and student_id from the payment table. P.course_code=e.course_code AND p.student_id=e.student_id How can we join the tables with these compound keys?Įasy! We just need to use a JOIN clause with more than one condition by using the AND operator after the first condition. In the second table ( payment), we have columns that are a foreign compound key ( student_id and course_code). In one joined table (in our example, enrollment), we have a primary key built from two columns ( student_id and course_code). The following diagram shows the pictorial representation of the Right Outer Join in SQL Server. In that case, the un-matching data will take the null value. If you’d like to get data stored in tables joined by a compound key that’s a primary key in one table and a foreign key in another table, simply use a join condition on multiple columns. The Right Outer Join in SQL Server is used to retrieve all the matching records from both the tables involved in the join as well as all the non-matching records from the right-hand side table. Let’s show each student’s name, course code, and payment status and amount. The payment table has data in the following columns: foreign key ( student_id and course_code, the primary keys of the enrollment table), status, and amount. The enrollment table has data in the following columns: primary key ( student_id and course_code), is_active, and start_date. To perform join between A and B using LEFT JOIN clause, you use the following statement: SELECT a, b FROM A LEFT JOIN B ON A.f B.f WHERE searchcondition Code language: SQL (Structured Query Language) (sql) The expression A.f B.f is a conditional expression. The student table has data in the following columns: id (primary key), first_name, and last_name. Our database has three tables named student, enrollment, and payment. You want to join tables on multiple columns by using a primary compound key in one table and a foreign compound key in another.
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