DQL

What
When
Where
Who
Why
How
How many

What is DQL?

DQL stands for Data Query Language. It is a type of SQL sub-language. These statements are used to select rows from a table or join tables together to retrieve data from multiple tables in a query. The most common DQL statement is the SELECT statement.

What

What is DQL?

DQL stands for Data Query Language. It is a type of SQL sub-language. These statements are used to select rows from a table or join tables together to retrieve data from multiple tables in a query. The most common DQL statement is the SELECT statement.

When to use DQL statements?

We use the DQL statement when we retrieve the data from a database. The benefits of this statement are:

  • It is a powerful and efficient language that can be used to retrieve data in a variety of ways.
  • It is a declarative language, which means that you specify what data you want to retrieve.

Where do we use DQL?

DQL can be used in a variety of places, including:

  • Web applications: It uses DQL to retrieve data from a database to display on a web page.
  • Desktop applications: It uses DQL to retrieve data from a database to populate a form.
  • Mobile applications: It uses DQL to retrieve data from a database to display on a mobile device.
  • Business intelligence tools: It uses DQL to retrieve data from a database to generate reports and dashboards.
  • Data mining tools: It uses DQL to retrieve data from a database to identify patterns and trends.

Who created DQL?

Donald D. Chamberlin and Raymond F. Boyce created DQL (Data Query Language) in the early 1970s

Why is the SELECT statement the most common DQL statement?

The SELECT statement is the most common DQL statement because it is used to select rows from a table. The SELECT statement can be used to specify which columns to return, as well as any conditions that must be met for a row to be selected. This makes the SELECT statement very versatile and useful for a wide variety of tasks.

For example, the SELECT statement can be used to:

  • Retrieve all rows from a table
  • Retrieve specific rows from a table based on a condition
  • Retrieve a subset of columns from a table
  • Retrieve data from multiple tables in a single query

The SELECT statement is also very efficient and can retrieve data quickly. This makes it the ideal choice for most data retrieval tasks.

How DQL differs from DDL?

DQL or Data Query Language is used to query data from a database. It is a subset of SQL and is used to select, insert, update, and delete data from a database.

DDL or Data Definition Language is used to define the structure of a database. It is used to create, alter, and drop tables, columns, and other database objects.

The main difference between DQL and DDL is that DQL is used to manipulate data, while DDL is used to manipulate the structure of a database.

How many different kinds of statements are there in DQL?

There are four different kinds of statements in DQL:

  • SELECT: This statement is used to select data from a database.
  • INSERT: This statement is used to insert new data into a database.
  • UPDATE: This statement is used to update existing data in a database.
  • **DELETE:**This statement is used to delete data from a database.