What is Implicit Joins?
Implicit joins in SQLite refer to joining tables in a query using the WHERE clause without explicitly using the JOIN keyword. This method of joining tables is considered implicit because the join condition is implied by the WHERE clause, rather than explicitly stated in a JOIN clause. Let’s understand through the below examples.
Consider the following two tables called STUDENTS and COURSES. Here STUDENTS consists of id,first_name, last_name and COURSES consist of id, course_name as Columns.
Implicit Joins( Database)
Example 1
Let’s Retrieve the first name and last name of students along with the name of the course they are enrolled in, based on matching IDs between the students and courses tables.
SELECT students.first_name, students.last_name, courses.course_name
FROM students, courses
WHERE students.id = courses.id;
Output:
Implicit Joins( Example-1 output)
Explanation: In the above query, We selects the first name and last name of students along with the name of the course they are enrolled in, based on matching IDs between the students and courses tables. It retrieves data from the “students” and “courses” tables where the ID of a student matches the ID of a course.
Example 2
Let’s Retrieve the first name and last name of students along with the name of the course they are enrolled in, without any specific condition for matching IDs between the students and courses tables.
SELECT students.first_name, students.last_name, courses.course_name
FROM students, courses;
Output:
Implicit Joins( Example-2 output)
Explanation: In the above query, We selects the first name and last name of students along with the name of the courses they are enrolled in. It retrieves data from the “students” table and the “courses” table, combining every row from the “students” table with every row from the “courses” table which effectively creating a Cartesian product of the two tables
Explicit vs Implicit Joins in SQLite
When working with SQLite databases, users often need to retrieve data from multiple tables. Joins are used to combine data from these tables based on a common column. SQLite supports two types of joins which are explicit joins and implicit joins. In this article, We’ll learn about Explicit vs implicit joins in SQLite along with their differences and some examples and so on.