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Introduction to MySQL Database Normalization Day 2
| Date post: | 27-Jul-2015 |
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Technology |
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Introduction to MySQLDatabase Normalization
Day 2
Relevance of normalization
• We could have store all the data in a single table like
• But there are several issues arise here
Emp_id Emp_name Emp_age Emp_email Fk_int_designation
Vchr_Desig_roles
1000 Deepak 45 [email protected]
Are Manager Handles all the district level operations
1001 Aneesh 23 [email protected] Sales person Will increase sales and ensure customer satisfaction
1002 Naveen 25 [email protected]
Sales person Will increase sales and ensure customer
satisfaction
1003 Jacob 25 [email protected]
Administrator Handles all the district level operations
Relevance of normalization
• We could have store all the data in a single table like
Emp_id Emp_name Emp_age Emp_email Fk_int_designation
Vchr_Desig_roles
1000 Deepak 45 [email protected]
Are Manager Handles all the district level operations
1001 Aneesh 23 [email protected] Sales person Will increase sales and ensure customer satisfaction
1002 Naveen 25 [email protected] Sales person Will increase sales and ensure customer satisfaction
1003 Jacob 25 [email protected]
Administrator Handles all the district level operations
Here designation is repeated for all the rows and where ever it repeats the designation role also has to repeat. This redundancy takes a lot of space to store and
is inefficient
Relevance of normalization
• We could have store all the data in a single table like
Emp_id Emp_name Emp_age Emp_email Fk_int_designation
Vchr_Desig_roles
1000 Deepak 45 [email protected]
Are Manager Handles all the district level operations
1001 Aneesh 23 [email protected] Sales person Will increase sales and ensure customer satisfaction
1002 Naveen 25 [email protected] Sales person Will increase sales and ensure customer satisfaction
1003 Jacob 25 [email protected]
Administrator Handles all the district level operations
Suppose if i want to modify the roles of any designation, i will have to do the same for all records in the table. Its time consuming and not an effective way to follow
Normalization• Normalization is the process of moving data into related
tables
• Will save data dependency and redundancy
• Save typing of repetitive data
• Reduce disk space
Types of Normalization
• There are several levels of normalization– 1st Normalization– 2nd Normalization– 3rd Normalization
First Normal Form
First Normal Form– Each field contains the smallest meaningful value– The table does not contain repeating groups of fields or
repeating data within the same field
To attain 1st normalized form what you have to do is•Create a separate field/table for each set of related data. •Identify each set of related data with a primary key
Table violating 1st Normal Form
Company (pk) Branches
Baabte Cochin, Calicut
baabtra Calicut,Trivandrum
It really is a bad setup that we are storing multiple values in a single column. For a table to be in 1st normalised form it should only have atomic values
Table violating 1st Normal Form
Company (Pk) Branche1 Branch2
Baabte Cochin Calicut
baabtra Calicut Trivandrum
It still in a bad set up , as we should not have multiple columns describing the same property of an entity.
Table conforming to 1st Normal Form
Company (pk) Branch (pk)
Baabte Cochin
Baabte Calicut
baabtra Calicut
baabtra Trivandrum
We have resulted in a 1st normalised table with primary key consists of two columns
Second Normalisation
Second Normalisation
– usually used in tables with a multiple-field primary key (composite key)
– each non-key field relates to the entire primary key– any field that does not relate to the primary key is placed
in a separate table• To attain 1st normalized form what you have to do is
•eliminate redundant data in a table •Create separate tables for sets of values that apply to
multiple records
Table violating 2nd Normal Form
Employee (pk) Skill (pk) WorkLocation
John IOS programmer Calicut
Mathew Java programmer Cochin
Thomas Android programmer
Trivandrum
Alex PHP programmer Banglore
Ram Java programmer Mumbai
John PHP programmer Delhi
Soozan doNet programmer Calicut
Primary key= { Employee,Skill }
Table violating 2nd Normal Form
Employee (pk) Skill (pk) WorkLocation
John IOS programmer Calicut
Mathew Java programmer Cochin
Thomas Android programmer
Trivandrum
Alex PHP programmer Banglore
Ram Java programmer Mumbai
John PHP programmer Delhi
Soozan doNet programmer Calicut
Here non key attribute do not fully depends on compete primary key. IeWorkLocation depends only on Employee and doesn’t depend on Skill (partial
dependency)
Primary key= { Employee,Skill }
Table conforming to 2nd Normal Form
Employee (pk)
Skill (pk)
John IOS programmer
Mathew Java programmer
Thomas Android programmer
Alex PHP programmer
Ram Java programmer
John PHP programmer
Soozan doNet programmer
Employee (pk)
WorkLocation
John Calicut
Mathew Cochin
Thomas Trivandrum
Alex Banglore
Ram Mumbai
John Delhi
Soozan Calicut
Third Normalisation
Third Normal Form• Usually used in tables with a single field primary key
--records do not depend on anything other than a table's primary key – each non-key field is a fact about the key– Values in a record that are not part of that record's key do
not belong in the table. In general, any time the contents of a group of fields may apply to more than a single record in the table, consider placing those fields in a separate table.
EMPNO (Primary Key)
FIRSTNAME LASTNAME WORKDEPTNO DEPTNAME
000290 John Parker OP11 Operations
000320 Ramlal Mehta SE21 Software Support
000310 Maude Setright OP11 Operations
Table violating 3rd Normal Form
EMPNO (Primary Key)
FIRSTNAME LASTNAME WORKDEPTNO DEPTNAME
000290 John Parker OP11 Operations
000320 Ramlal Mehta SE21 Software Support
000310 Maude Setright OP11 Operations
Table violating 3rd Normal Form
Here all the fields are not completely depend on Primary key.Ie Dept Name column only depends on DeptNo.And deptno depends on the EMPNO.
Ie its a transitive dependency. Which should be avoided
Table conforming to 3rd Normal Form
EMPNO (Primary Key)
FIRSTNAME LASTNAME WORKDEPTNO
000290 John Parker OP11
000320 Ramlal Mehta SE21
000310 Maude Setright OP11
WORKDEPTNO DEPTNAME
OP11 Operations
SE21 Software Support
OP11 Operations
Here all the fields are completely depend on Primary key.
End of Day2
