database table Design 1

Time: 2015.4.21.17:50

2 years of learning programming, the first analysis of requirements. Summarize my understanding of the building table.

1. The table is stored in the database, and the table is a collection of objects.

2. The fields in the table are object properties.

3. The relationship between tables and tables is 1:1,1:n or n:1,n:n.

4.1:1 of understanding

Team Address

Team ID	Team Name	Address ID (foreign key)
QID	NAME	Did

Address ID	Address name
Did	NAME

This is a foreign key association. Through did.

Team Address

Team ID	Team Name
QID	NAME

Team ID	Address name
QID	NAME

This is the primary key association, through the QID

Analysis: Team and address relationships. A team has an address and an address for a team (regardless of the 2 teams sharing an address).

Personal thinking: I think 1:1 is very interesting. If there is no other table associated with the Address table, the Address table can not, directly in the team table to add a field "address name." Because the team table and Address Table 1:1. That is, the team table and the "address name" 1:1. This is the table corresponding to the property.

5.1:n or N:1

People provinces

Person ID	Id
Name	NAME
Save ID	Sid

Save ID	Province name
Sid	NAME

Analysis: A person belongs to a province, a province has many people.

Personal thinking: This situation has only one connection. The person is the child table, the province is the total table. The Pipe Union foreign key is placed in the child table. Why is it? This understanding: In the human table, a person only corresponds to a province ID, that is, a province. If the Union field is placed in the

In the provinces table, that is the table with a "Person id" field. The object of the table is a province with a "Person id", is a person. But it does not match the actual. The reality is: There are many people in a province.

6.n:n

Student Selection Course

School Number	Name
Sid	NAME

Course ID	Course Name
XID	NAME

Learning-Class

School Number	Course Number
Sid	XID

Analysis: A student has more than one course, and a class has multiple students.

Personal thinking: This many-to-many is also an association. You need to build an intermediate table that is the primary key of the associated table. Sid and Xid are the federated primary keys of the intermediate table (Learning-Class). There is no need to add any related words to the Student table and timetable.

database table Design 1