Basic operations of MySQL auto correlation query

Basic operations of Auto Association query

• preparation ：
• sql The data file is accessed from the following connection
  The extraction code is ：n0ug
  
  

Query all provinces and autonomous regions

select * from province where pid=0;

Statistics on all provinces, autonomous regions and municipalities directly under the central government in China ：

What cities are there in Guangdong Province ( Imagine two tables )：

select p.name,s.name from province as p inner join province as s on s.pid=p.id where p.name = " Guangdong province, ";