primary key concept is critical to an efficient relational database. Without
the primary key and closely related foreign key concepts, relational databases
would not work.
all individuals deal with primary keys frequently but unknowingly in everyday
life. For example, students are routinely assigned unique identification (ID)
numbers, and all U.S. citizens have government-assigned and uniquely
identifiable Social Security numbers.
example, a database must hold all of the data stored by a commercial bank. Two
of the database tables include the CUSTOMER_MASTER, which stores basic and
static customer data (name, date of birth, address, Social Security number,
etc.) and the ACCOUNTS_MASTER, which stores various bank account data (account
creation date, account type, withdrawal limits or corresponding account
uniquely identify customers, a column or combination of columns is selected to
guarantee that two customers never have the same unique value. Thus, certain
columns are immediately eliminated, e.g., surname and date of birth. A good
primary key candidate is the column that is designated to hold Social Security
numbers. However, some account holders may not have Social Security numbers, so
this column’s candidacy is eliminated. The next logical option is to use a
combination of columns, such as adding the surname to the date of birth to the
email address, resulting in a long and cumbersome primary key.
best option is to create a separate primary key in a new column named
CUSTOMER_ID. Then, the database automatically generates a unique number each
time a customer is added, guaranteeing unique identification. As this key is
created, the column is designated as the primary key within the SQL script that
creates the table, and all null values are automatically rejected.
account number associated with each CUSTOMER_ID allows for the secure handling
of customer queries and also demonstrates why primary keys offer the fastest
method of data searching within tables. For example, a customer may be asked to
provide his surname when conducting a bank query. A common surname (such as
Smith) query is likely to return multiple results. When querying data,
utilizing the primary key uniqueness feature guarantees one result.
The primary key concept is critical to an efficient relational database