Author: Awais Khan
-
Show/List Triggers
The show or list trigger is much needed when we have many databases that contain various tables. Sometimes we have the same trigger names in many databases; this query plays an important role in that case. We can get the trigger information in the database server using the below statement. This statement returns all triggers…
-
Create Trigger
In this article, we are going to learn how to create the first trigger in MySQL. We can create a new trigger in MySQL by using the CREATE TRIGGER statement. It is to ensure that we have trigger privileges while using the CREATE TRIGGER command. The following is the basic syntax to create a trigger:…
-
Trigger
A trigger in MySQL is a set of SQL statements that reside in a system catalog. It is a special type of stored procedure that is invoked automatically in response to an event. Each trigger is associated with a table, which is activated on any DML statement such as INSERT, UPDATE, or DELETE. A trigger is called a…
-
Composite Key
A composite key in MySQL is a combination of two or more than two columns in a table that allows us to identify each row of the table uniquely. It is a type of candidate key which is formed by more than one column. MySQL guaranteed the uniqueness of the column only when they are combined. If…
-
Foreign Key
The foreign key is used to link one or more than one table together. It is also known as the referencing key. A foreign key matches the primary key field of another table. It means a foreign key field in one table refers to the primary key field of the other table. It identifies each row of…
-
Primary Key
MySQL primary key is a single or combination of the field, which is used to identify each record in a table uniquely. If the column contains primary key constraints, then it cannot be null or empty. A table may have duplicate columns, but it can contain only one primary key. It always contains unique value into a…
-
Unique Key
A unique key in MySQL is a single field or combination of fields that ensure all values going to store into the column will be unique. It means a column cannot stores duplicate values. For example, the email addresses and roll numbers of students in the “student_info” table or contact number of employees in the “Employee”…
-
Difference between MySQL Union and Join
Union and Join are SQL clauses used to perform operations on more than one table in a relational database management system (RDBMS). They produce a result by combining data from two or more tables. But, the way of combining the data from two or more relations differ in both clauses. Before making a comparison, we are going to discuss…
-
Difference between Left Join and Right Join
MySQL has mainly two kinds of joins named LEFT JOIN and RIGHT JOIN. The main difference between these joins is the inclusion of non-matched rows. The LEFT JOIN includes all records from the left side and matched rows from the right table, whereas RIGHT JOIN returns all rows from the right side and unmatched rows from…
-
Natural Join
When we combine rows of two or more tables based on a common column between them, this operation is called joining. A natural join is a type of join operation that creates an implicit join by combining tables based on columns with the same name and data type. It is similar to the INNER or LEFT JOIN, but we…