SQL Basic Operations--join Multi-table joint search

SQL join: use to query data from these tables based on the relationship between the columns in two or more tables.

Join and key: Sometimes we need to get the results from two or more tables in order to get the full result. We need to execute the join. Tables in the database can be linked by keys. The primary key (Primary key) is a column, and the value of each row in the column is unique. In the table, the value of each primary key is unique. The purpose of this is to cross-bind the data between tables without repeating all the data in each table.

Please see the "Persons" table:

SQL Basic Operations--join Multi-table joint search