A query language is a computer programming language used to retrieve information from a database. It is a set of keywords and symbols that are used to construct queries, which are instructions to the database to return specific data.

Query languages can be classified into two main types:

• Procedural query languages specify the steps that the database must take to retrieve the desired data. For example, a procedural query language might specify that the database should first sort the data by a certain field, and then select the top 10 records.
• Non-procedural query languages specify the desired data without specifying the steps that the database must take to retrieve it. For example, a non-procedural query language might simply specify that the database should return all records where the name field is equal to “John Smith”.

The most common query language is Structured Query Language (SQL), which is a non-procedural query language. SQL is used to interact with relational databases, which are the most common type of database.

Other examples of query languages include:

• NoSQL query languages are used to interact with NoSQL databases, which are a type of database that does not follow the relational model. NoSQL databases are often used for big data applications.
• Information retrieval query languages are used to interact with search engines. These languages are designed to find documents that are relevant to a user’s query, even if the documents do not contain the exact words that the user typed in.

Query languages are an essential tool for working with databases. They allow users to easily retrieve the data that they need, without having to know how the database is structured or how the data is stored.

Here are some of the benefits of using query languages:

• Ease of use: Query languages are designed to be easy to use, even for users who are not familiar with programming.
• Power: Query languages can be used to retrieve complex data sets, and to perform sophisticated queries.
• Flexibility: Query languages can be used to interact with a wide variety of databases.
• Portability: Query languages are often portable, meaning that they can be used with different databases on different platforms.

Overall, query languages are a powerful and versatile tool for working with databases. They are essential for anyone who needs to retrieve data from a database, regardless of their level of technical expertise.