Page 50 - Database-En-V3

Then the primary key of the table is determined:

• Primary key:
It is a table field in which data is not allowed to be duplicated and
is used to distinguish table records. It is used to link tables logically
and can be searched through to obtain valid results within the
table
Key column specifications:

The primary key is the field that distinguishes records from other records. It consists of only one field
and is characterized by the following:

• No two values in a primary key field are the same.
• None of its values must be null.
• Preferably a number

Example: In a table containing student data, the most appropriate
primary key for the table is “university number,” as it is: Contains values
that cannot be repeated.

No two students at the university have the same university number or Phone
the same student code. number

University ID the name Specialization the level reward Regularity date of birth the address

12321 Cairo 1/3/2010 yes 1000 1 mathematics Manal 433001
12414 Cairo 1000 2
12414 Cairo 1000 1 Mohammed

2/11/2009 yes Physics Maha 433002
Ahmad

4/5/2010 yes Mathematics Names 433003
Khaled

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