Data Manipulation Language, or DML for short, is a powerful tool that allows you to manage and manipulate data in a relational database. Whether you're a seasoned developer or just starting, understanding DML is essential for working with databases and creating dynamic, data-driven applications. In this article, we'll dive deeply into DML and explore the various commands and techniques used to manage data in a structured and organized manner. From SELECT and INSERT to UPDATE and DELETE, we'll cover everything you need to know to master DML and take your database skills to the next level. So, whether you're looking to become a pro at manipulating data or just want to learn more about DML, read on and discover how this powerful language can help you unlock the full potential of your data!

What is Data Manipulation Language (DML)?

Data Manipulation Language (DML) is a subset of SQL (Structured Query Language) that is used to manage and manipulate data in a relational database. DML commands are used to insert, update, delete, and retrieve data from a database. These commands allow users to change the data stored in the database without affecting the database schema or the definition of the database objects. An interesting fact, the no-code platform AppMaster, with which you can create a web application, mobile application, and backend, has a business process editor based on DML.

Types of DML Statements

  • SELECT statement: The SELECT statement is used to retrieve data from one or more tables in a database. The result of a SELECT statement is a table, also known as a result set. The SELECT statement can also be used to retrieve data from multiple tables using a join operation.
  • INSERT statement: The INSERT statement is used to insert new rows of data into a table. The INSERT statement can be used to insert data into a single table or multiple tables at once.
  • UPDATE and DELETE statement: The UPDATE statement is used to modify existing data in a table, while the DELETE statement is used to delete data from a table. Both statements can be used to update or delete data from a single table or multiple tables at once.

In addition to these statements, DML also includes statements such as MERGE and CALL. The MERGE statement is used to combine the data from two tables into one, while the CALL statement is used to execute a stored procedure.

It's worth noting that DML statements are executed within a transaction, which means that all the changes made by DML statements are committed or rolled back as a single unit of work. This allows users to ensure that the data remains consistent and accurate even when multiple DML statements are executed simultaneously.

DML commands are executed using SQL, and they are often used in conjunction with other SQL commands, such as the Data Definition Language (DDL) commands, to create and manage a relational database. For example, a DDL command like CREATE TABLE is used to create a table, and then DML commands are used to insert, update, and retrieve data from that table. It's important to note that DML statements are executed within a transaction, which means that all the changes made by DML statements are committed or rolled back as a single unit of work.

In summary, Data Manipulation Language (DML) is a powerful set of commands used to manage and manipulate data in a relational database. The SELECT, INSERT, UPDATE, and DELETE commands are most commonly used in DML, allowing users to make changes to the data stored in the database without affecting the database schema or the definition of the database objects. DML statements are executed using SQL and are often used in conjunction with DDL commands to create and manage a relational database.

FAQ

What is Data Manipulation Language (DML)?

Data Manipulation Language (DML) is a subset of SQL that is used to manage and manipulate data in a relational database.

What are some examples of DML statements?

Some examples of DML statements include SELECT, INSERT, UPDATE, and DELETE.

How do I use the SELECT statement in DML?

The SELECT statement is used to retrieve data from one or more tables in a database. The basic syntax of a SELECT statement is "SELECT column1, column2, ... FROM table_name."

How do I use the INSERT statement in DML?

The INSERT statement is used to add new rows of data to a table. The basic syntax of an INSERT statement is "INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...)."

How do I use the UPDATE statement in DML?

The UPDATE statement is used to modify existing data in a table. The basic syntax of an UPDATE statement is "UPDATE table_name SET column1 = new_value1, column2 = new_value2, ... WHERE some_column = some_value."

How do I use the DELETE statement in DML?

The DELETE statement deletes existing data in a table. The basic syntax of a DELETE statement is "DELETE FROM table_name WHERE some_column = some_value."

What are some best practices for using DML statements?

It is important to use WHERE clauses in your DML statements to ensure that you are only modifying or deleting the intended data. It is also a good idea to use transaction management and back up your data before making any changes.

Can DML statements be used in stored procedures?

Yes, DML statements can be used in stored procedures, which are pre-compiled sets of SQL statements that can be stored in a database and executed as a single unit.

Can DML statements be used to modify multiple tables at once?

No, DML statements can only be used to modify one table at a time. If you need to modify data in multiple tables, you will need to use multiple DML statements or use a transaction to ensure that all the changes are made atomically.