Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I try to attempt to explain normalization in layman terms here. First off, it is something that applies to relational database (Oracle, Access, MySQL) so it is not only for MySQL.</p> <p>Normalisation is about making sure each table has the only minimal fields and to get rid of dependencies. Imagine you have an employee record, and each employee belongs to a department. If you store the department as a field along with the other data of the employee, you have a problem - what happens if a department is removed? You have to update all the department fields, and there's opportunity for error. And what if some employees does not have a department (newly assigned, perhaps?). Now there will be null values.</p> <p>So the normalisation, in brief, is to avoid having fields that would be null, and making sure that the all the fields in the table only belong to one domain of data being described. For example, in the employee table, the fields could be id, name, social security number, but those three fields have nothing to do with the department. Only employee id describes which department the employee belongs to. So this implies that which department an employee is in should be in another table.</p> <p>Here's a simple normalization process.</p> <pre><code>EMPLOYEE ( &lt; employee_id &gt;, name, social_security, department_name) </code></pre> <p>This is not normalized, as explained. A normalized form could look like</p> <pre><code>EMPLOYEE ( &lt; employee_id &gt;, name, social_security) </code></pre> <p>Here, the Employee table is only responsible for one set of data. So where do we store which department the employee belongs to? In another table</p> <pre><code>EMPLOYEE_DEPARTMENT ( &lt; employee_id &gt;, department_name ) </code></pre> <p>This is not optimal. What if the department name changes? (it happens in the US government all the time). Hence it is better to do this</p> <pre><code>EMPLOYEE_DEPARTMENT ( &lt; employee_id &gt;, department_id ) DEPARTMENT ( &lt; department_id &gt;, department_name ) </code></pre> <p>There are first normal form, second normal form and third normal form. But unless you are studying a DB course, I usually just go for the most normalized form I could understand.</p> <p>Hope this helps.</p>
    singulars
    1. This table or related slice is empty.
    1. PONormalization in MYSQL
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USTim
    1. USExtrakun
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PONormalization in MYSQL
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COthanks for you help man...
      singulars
      1. PO
      1. USFero
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload