Therefore, they’re used in the payment table as a foreign key. Note that the student_id and course_code columns form a primary key in the enrollment table. 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). A product may have multiple barcodes, which is why I've separated it off into it's own table. In one joined table (in our example, enrollment), we have a primary key built from two columns ( student_id and course_code). You can use grouping to get only one row per Name. 26 I have two MySQL tables, products, and barcodes. 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. If you are using MySQL 8+, then ROWNUMBER combined with pivoting logic provides one way: WITH cte AS ( SELECT, ROWNUMBER () OVER (PARTITION BY id ORDER BY val) rn FROM yourTable ) SELECT id, MAX (CASE WHEN rn 1 THEN val END) AS val1, MAX (CASE WHEN rn 2 THEN val END) AS val2, MAX (CASE WHEN rn 3 THEN val END) AS val3, MAX. 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. The student table has data in the following columns: id (primary key), first_name, and last_name. I have a sql table having multiple rows in which i want to get single row from same column value in my case SKU Column.I want to merge multiple rows from same sku value into one row having all values of attributeid and attributevalue. 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. If youd like to get data stored in tables joined by a compound key thats a primary key in one table and a foreign key in another table, simply use a join.
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