This exception occurs when our code attempts to perform a SQL operation that would violate an integrity constraint defined in the database schema. This error could occur for a variety of reasons, such as attempting to insert a duplicate primary key value into the table or failing to provide values for one or more required columns.
Let's run through an example to understand it better-
CREATE TABLE abc_table(
user_name varchar(255) NOT NULL PRIMARY KEY,
DB::table(' abc_table ')->insert($data);
In the above example abc_table has a column user_name with the primary key constraint.
We are trying to insert duplicate value in the user_name column thus it is giving us an un-called error.