MySQL Common query statement summary (not updated regularly ....) ）

In this article I will introduce some examples of common SQL statement directories in everyday programming:

• # 1. Establishment of the database

• # # 2. Common queries

# 1. An example of a database is given in the form of an ER diagram:

4 relational patterns from this conversion: Note: The underscore is a straight line key, and the underscore is a red dashed line for the foreign key

This allows you to create the following database: C: S: SC: T:

For a specific database setup script, check out my github

# # 2. Common queries

• Query for the minimum age of four persons (sorted by age from small to large, if same age, in name order)

SELECT * from S  ORDER by age Asc,convert (SName USING GBK) LIMIT 4

• Check the first two courses of exam time (Examdate is datetime type data)

SELECT * from CORDER by Examdate Asc,convert (cName USING GBK) LIMIT 2

• Get three student data at a random

SELECT * from SORDER by RAND () LIMIT 3

MySQL Common query statement summary (not updated regularly ....) ）