Selection Operation in Query Processing in DBMS
- Picking out certain information from a database is like finding the perfect pieces for a puzzle. SQL, which stands for Structured Query Language, helps us do this by using special instructions called statements. One of these statements is ‘SELECT‘, and it works together with another part called the ‘WHERE’ clause. The ‘SELECT‘ statement tells the computer which specific pieces of the puzzle, or columns, we want to look at. But the ‘WHERE‘ clause is like giving extra clues about the pieces we need. It sets rules that the data must follow in order to be included in our final puzzle picture, or result set.
SELECT column1, column2, ...
FROM table_name
- First, create a table by th name of example ‘Customer‘:
CREATE TABLE Customer(
CustomerID INT PRIMARY KEY,
CustomerName varchar(255),
Name varchar(255),
Country varchar (255),
Age int(3),
Phone int(10)
);
- then, insert data in the table
INSERT INTO Customer(CustomerID,CustomerName,LastName,Country,Age,Phone)
VALUES
(1,"Shubham","Thakur","India",23,1234567890),
(2,"Aman","Chopra","Australia",21,1234567890),
(3,"Naveem","Tulasi","Sri Lanka",24,1234567890),
(4,"Aditya","Arpan","Austria",21,1234567890),
(5,"Nishant","Jain","Spain",22,1234567890);
Selection Operation in Query Processing in DBMS
Regarding query processing, the term “selection” operation denotes fetching particular rows from a database table that fulfill some given condition or conditions. Why is this important? Because databases manage vast volumes of information, users must be able to narrow down their searches based on different parameters. The next few lines explain how selection works during query processing.
Databases are like huge libraries where information is stored in tables. The “selection” operation is like finding the books you need from all the shelves. It helps you pick out specific rows or records from a table that match certain rules or conditions you set. For example, if you want to find all the books written by a particular author, you would use the selection operation to look through the “Author” column and gather only those rows where the author’s name matches what you searched for. This operation is super important because it allows you to extract just the data you need from the vast amounts of information stored in databases. It’s often combined with other operations like choosing specific columns (projection), combining data from multiple tables (join), and calculating things like sums or averages (aggregation) to create complex database queries.