BQ JOIN checker

In BigQuery SQL, you can check the change in the number of records before join and create a join relationship diagram

【OVERVIEW】 By inputting standardSQL including BigQuery join clause, generate SQL to check the change in the number of records before and after join, and use the SQL for verification to detect unintended increase/decrease of records in join clause. I can. You can also visualize the SQL structure by analyzing the JOIN clause relationships. 【USE CASE】 When creating a mart SQL that connects sales and product data, etc., you can check from the record increase/decrease whether there is a non-normalization method. Examples of incorrect denormalization methods include the following possibilities: ・join key is wrong ・The id of the products table is not PK ・Join key is missing (sales.product_id contains NULL)