Working with Data Sources 3

Posted 2020-08-20 阿难的机器学习计划

SQL And Database:

1.SQL query is to request the data from the database.

2.We use SELECT command to pick the specific column from the database.

　　SELECT rank,major # This command will return a list which contains the data completely follow the order of column it selected. 

　　FROM recent_grads;

3.Use WHERE command to select certain rows which satisfy the condition.

　　SELECT Major,Employed FROM recent_grads WHERE Employed > 10000 

4.Use LIMIT to specify certain number of results.

5.Use Order by to specify the order for the rows.(desc and asc)　　

6.Order by can also specify mutiple columns by orders.