Understand the SQL intersection command

Introduction

An essential tool for data handling is the SQL that crosses. In essence, Intersect joins two tables and produces a set of results that contains the intersection (common records) of the two tables. We will study syntax, applications and fundamental examples in our table of examples in this publication.

Overview

• Understand the purpose and basic syntax of the SQL intersection clause.
• Identify scenarios where the intersection clause can be applied effectively.
• Implement the intersection clause to find common records between two tables.
• Use the intersection clause in conjunction with where and order by clauses to consult advanced.
• Recognizes the advantages of using the intersection clause to simplify complex queries and improve performance.

What do you cross SQL?

Intersect only returns the ranks that are present in the two sets of results (results sets of the selected instructions). It is used to find common records: some real -world scenarios where the intersection will be used are:

• Find common employees between different departments.
• Find common customers between different companies.
• Patient records stored in different departments.

Basic Syntax of Intersection

The basic way of finding the intersection of two tables is to put intersection between two selected statements. The above code is the basic syntax to find the intersection.

SELECT column1, column2, ...
FROM table1
INTERSECT
SELECT column1, column2, ...
FROM table2;

Creating sample data

We have now learned to create sample data:

CREATE TABLE Employees (
    employee_id INT PRIMARY KEY,
    name VARCHAR(50),
    department VARCHAR(50),
    salary DECIMAL(10, 2)
);

CREATE TABLE Contractors (
    contractor_id INT PRIMARY KEY,
    name VARCHAR(50),
    department VARCHAR(50),
    hourly_rate DECIMAL(10, 2)
);

Creating necessary tables:

INSERT INTO Employees (employee_id, name, department, salary) VALUES
(1, 'Alice', 'HR', 60000),
(2, 'Bob', 'Engineering', 80000),
(3, 'Charlie', 'Marketing', 50000),
(4, 'David', 'Engineering', 75000);

INSERT INTO Contractors (contractor_id, name, department, hourly_rate) VALUES
(101, 'Eve', 'Engineering', 50),
(102, 'Frank', 'HR', 45),
(103, 'Grace', 'Engineering', 55),
(104, 'Charlie', 'Marketing', 60);

Insert required samples in the table:

Intersection implementation

Now we will implement SQL Intersect.

Find common names between the table

SELECT name FROM Employees
INTERSECT
SELECT name FROM Contractors;

The common names between the two tables, employees and contractors, will be located by this code. Common names Alice, Bob and Charlie are visible in the results set, as seen in the image above.

Find common departments

SELECT department FROM Employees
INTERSECT
SELECT department FROM Contractors;

We notice that the results set does not include the sales department as it is not present in the employee table.

Combining more columns

SELECT name, department FROM Employees
INTERSECT
SELECT name, department FROM Contractors;

We see that the results set includes records with the same name and department of both tables.

Interrupts with where the clause

SELECT name 
FROM Employees 
WHERE department="Engineering"
INTERSECT
SELECT name 
FROM Contractors 
WHERE department="Engineering";

This makes our filter more advanced, we can find exactly records that satisfy our condition. We can see that a common name with the engineering department present in the two tables is Bob.

Intersect with the clause in order

SELECT name 
FROM Employees 
WHERE salary > 50000
INTERSECT
SELECT name 
FROM Contractors 
WHERE hourly_rate > 50
ORDER BY name;

From the statement we can see that we are able to filter our names that have a salary greater than 50000 and an hour rate above 50 and also present in the two tables. After all these conditions, we sort them using the clause in order. We can implement complex conditions with the help of intersection and other clauses.

SQL advantages cross

• Simplicity: Simplify complex queries that need to find common records.
• Efficiency: Optimized for performance, especially with indexed columns.
• Legibility: Improves the readability of the query by clearly defining the intersection operation.

Conclusion

We saw some of the use cases, examples of examples of intersection. We can see that it is a very useful tool of SQL. With a good understanding of the intersecting we can get the best of our data to find information, cross -seeing coherence, etc.

Frequent questions