Searching Information in a Relational Database

Understanding Relational Databases

A relational database is a type of database that stores and organises data in tables related by common attributes.
It employs a structure that allows us to determine relationships between different sets of data.
This design feature is fundamental to performing effective searches on the database.

Searching Techniques

Queries are a fundamental tool to search for specific information in a relational database.
The simplest query is a SELECT statement, used to retrieve data from one or more tables.
Queries can contain criteria to narrow down the search. For example, SELECT * FROM Customers WHERE Country = ‘UK’.
Using logical operators, such as AND, OR, and NOT, can help refine search results.
Equally, comparing different attributes of the data (e.g., age, address, id) using comparison operators (=, <, >, <=, >=, <>), makes specific information searching possible.

Sorting and Filtering

Sorting data is another fundamental way to sift through information in databases. It is done using the ORDER BY command.
The sorting command can arrange data in an ascending (ASC) or descending (DESC) order.
Filtering helps to narrow down the data in a table by specific criteria. This is often done through a WHERE clause in the SQL query.

Joining Tables

When information occurs in more than one table, use of the JOIN command to link these tables based on common attributes becomes necessary.
Joining tables is key in relational databases as it allows comprehensive and complex data retrieval across tables.

Standard Search Functions

Functions like SUM, AVG, MIN, MAX, and COUNT can be used within a SELECT statement for a more detailed search.
Using these aggregate functions, users can analyse and navigate large volumes of data effectively.

Practice with Sample Databases

To have a solid understanding of searching in relational databases, practice with sample databases is advisable.
Freely available sample databases provide valuable experience in database querying and data manipulation.