Self Join in SQL - видео

A self join in SQL is where you write a query on one table that joins to the same table a second time. Its used when you have a record in the table that refers to another record in the same table. A common example is employees and managers or product categories. Anything with a hierarchical data setup may use an SQL self join. This video shows you what an SQL self join is how to write one and how to overcome issues with column names and missing data. You can find out more about joins overall in...
Источник видео: RuTube.ru (Технологии и интернет)