SQL Server primary key, use of foreign keys, and use of subqueries November 20

This morning, I learned about the use of primary and foreign keys in SQL Server and how to establish the connection between primary key and foreign key.

In the afternoon, I learned how to apply the subquery inside SQL Server, and also practiced the use of functions (String functions, aggregate functions).

Today's summary: by learning to understand the use of primary and foreign keys, as well as subqueries (select query nesting) usage, subqueries put a small scope in parentheses, and then a large range of inclusion.

SQL Server primary key, use of foreign keys, and use of subqueries November 20