Some notes of MySQL

Three paradigms of database

• First normal form ： emphasize The atomicity of a field , The meaning of a field is indivisible , Accurately express the meaning of its field ;

• Second normal form ： emphasize Uniqueness of records , A primary key can uniquely identify a data , No redundant data ;

  surface ： Student number 、 The student's name 、 Course 、 credits

• Third normal form ： emphasize Redundancy of fields , Any field of a table cannot be derived from other fields , The required field is not Rongyou , namely There is no transitive relationship ;

  surface ： Student number 、 full name 、 Age 、 The name of the College 、 College phone ;

  • There are transitive dependencies , Student number -> Student -> My college -> College phone