Query languages, often known as DQLs or Data Query Languages, are computer languages that are used to make various queries in information systems and databases. The Structured Query Language (SQL) is a well-known example. DQL statements are used to query the data contained in schema objects. The primary goal of the DQL Command is to return a schema relation depending on the query supplied to it.
In this article, we will dive deeper into the Data Query Language (DQL) according to the GATE Syllabus for (Computer Science Engineering) CSE. Keep reading ahead to learn more.
Table of Contents
What is Data Query Language (DQL)?
The DQL statements can be used in order to query the data and information contained in schema objects. The goal of the DQL Commands is to return a schema relation on the basis of the query supplied to them.
Definition of DQL
DQL is a portion of a SQL statement that allows you to get and organise data from a database. You can use the SELECT command to extract data from a database in order to perform actions on it. It is the same as the projection operation in relational algebra. The result of a SELECT statement on a table or collection of tables is compiled into a new temporary table, which is subsequently displayed or received by a program, i.e. a front-end.
The chosen clause, which would be the first and one of the last clauses of a select statement, is examined by the database server. The reason for this is that before we can determine what to include in the final result set, we need to know all the alternative columns that can be included.
Syntax
SELECT expression FROM table_x WHERE code_conditions;
Example
SELECT Stu_Name FROM Student WHERE Phone = 9039462908;
The command given above would select the record from the table ‘Student’ where the phone number is ‘9039462908’.
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