1/9/2023 0 Comments Create join in idatabaseIf we check the Products table in the Data Reference sidebar, we’ll see that it has two connections, one to the Orders table, and one to the reviews table. ![]() In this case, the Orders table contains a product_id, which refers to a specific row in the Products table. By foreign key, we mean a column that references the entity key in another table. The same is true of products in the Products table: each row is a product with an ID. In the Orders table, each row is an order with an ID. We’ve also aliased each table ( orders AS o and products AS p), so you can tell in the SELECT statement which table each field comes from ( o.created_at comes from the orders table, and so on).īy entity key, we mean a column in a table that contains each row’s unique identifier. ![]() This query tells the database that the rows in the Orders table can be combined with the rows in the Products table by “lining up” the foreign keys in the Orders table to the entity keys (also called the primary keys) of the Products table. It’s just there to point out the key part of the code: the join statement. Note that the comment (the line starting with -) isn’t necessary. JOIN products AS p ON o.product_id = p.id For example, we want to know the order date, ID, and total, but also include some info about the product ordered. Let’s say we want to ask a question that returns rows with columns from multiple tables. This article shows how to create joins using SQL, and you can follow along in Metabase by clicking on + New, choosing SQL Query, and selecting Raw data > Sample database. You’re taking the rows from two (or more) different tables and returning a new set of rows that combines columns in both tables. ![]() Note that the term “join” is somewhat misleading, as you’re not connecting the tables. (Note that joins only work with relational databases.)įor a background on joins, check out Joins in Metabase, which walks through how to create joins using the query builder-no code necessary. To do that, you’ll need to use a JOIN to tell your database how the rows from one table relate to the rows in the other table. You have data in one table that you want to combine with data from another table.
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