The concept of database code, the code examples of links with the paradigm-CodePudding

May I ask you, the in A relational schema, if each attribute can be uniquely identifies A tuple, for example, in A (id, employee number, fingerprint), is this A full code? Is that all the attributes of a code or all attributes are code

CodePudding user response:

this is a full code? Is that all the attributes of a code or all attributes are code

In business, these three attributes are the only code, so when designing the data of physical design, you can set up three yards (the only key), each code is a single attribute,

However, put three attributes together, build a combination of the code, and then the business is not consistent,

CodePudding user response:

[face] qq: 37. GIF [/fac

reference 1st floor selling fruit net reply:

this is a full code? Is that all the attributes of a code or all attributes are code

In business, these three attributes are the only code, so when designing the data of physical design, you can set up three yards (the only key), each code is a single attribute,

However, put three attributes together, build a combination of the code, and then the business is not consistent,

That this belongs to the third paradigm for? If there is a one-to-one relationship, like id number, and employee number in the database functions rely on, then, the former determine the latter or is it the latter decides the former

CodePudding user response:

refer to the second floor Excel_lent response:

[face] qq: 37. GIF [/fac

That this belongs to the third paradigm for? If there is a one-to-one relationship, like id number, and employee number in the database functions rely on, then, the former determine the latter or is it the latter decides the former

Whether to belong to the third paradigm, to list all the attributes, to determine,

Id and employee number, who is to decide who, the question to the understanding, as this is a list of the company's employees, must be employee number decision id number,

CodePudding user response:

reference 3 floor selling fruit net reply:

Quote: refer to the second floor Excel_lent response:

[face] qq: 37. GIF [/fac

That this belongs to the third paradigm for? If there is a one-to-one relationship, like id number, and employee number in the database functions rely on, then, the former determine the latter or is it the latter decides the former

Whether to belong to the third paradigm, to list all the attributes, to determine,

Id and employee number, who is to decide who, the question to the understanding, as this is a list of the company's employees, must be employee number decision id number,

If there is only a few attributes, so is can be judged belongs to which model