In an era where data has become a valuable resource for many activities, managing and searching for information quickly and accurately is an essential requirement for individuals and organizations. With the rapid increase in data, the need to retrieve information is becoming more important than ever.

To visualize it more easily, searching for a book in a scientifically arranged library will be much simpler than searching in a messy bookstore. Similarly, in database management, data queries help find the necessary information quickly and accurately.

Data queries play a key role in information exploitation, helping to meet the need to use data in many different situations, especially in the current era of data explosion.

What is a query?

A data query is a request or question to provide information from a system. In computer science, queries are both intended to search for data, with the main difference being the source of information retrieved from the database.

What is a database query?

Database queries can be divided into two main types: select queries and action queries. Select queries are requests to retrieve data from the database, while action queries are requests to perform additional operations on the data, such as inserting, updating, or deleting data.

In order for the database to understand and process the query request, the user needs to use a predefined query language, such as SQL (Structured Query Language). This is a popular language that helps users create accurate and efficient queries.

In the context of database management, a query means a request to find and provide information from the database. When a user executes a query, the database engine retrieves information from data tables (or a combination of tables) and converts the data into an understandable format, such as a table, text, or image.

Query results will help users examine and analyze information, thereby making decisions or delving deeper into the issues being researched.

What is a query in SQL?

A query in SQL is a request or statement executed in a database to retrieve, edit, or manage data. SQL (Structured Query Language) is the most popular standard query language used to execute queries in a database. This is an important language in interacting and manipulating with databases, helping users retrieve and process data effectively.

Although Microsoft SQL is the most popular SQL language, there are many other types of databases and query languages, such as NoSQL databases and related query languages ​​such as CQL (Cassandra Query Language), DMX (Data Mining Extensions), Cypher (Neo4j) and XQuery.

What is the difference between SQL and NoSQL?

When choosing a database, organizations often base their decision on the data structure and decide whether to use a relational (SQL) or non-relational (NoSQL) database. Here are some of the differences between SQL and NoSQL:

• Scalability: NoSQL databases are horizontally scalable, easily handling large amounts of data by distributing them across multiple servers. Meanwhile, SQL databases scale up, i.e., upgrading hardware to handle more data.
• Data schema: SQL databases have a predefined schema, i.e., the data structure must follow a certain model (relational). In contrast, NoSQL databases use a dynamic schema, which is suitable for unstructured data and can be flexible with data types such as documents, graphs, key values, or multi-column stores.

While both SQL and NoSQL are viable options, choosing between the two types of databases depends on the specific needs and requirements of each project.

How does a database query work?

A database query can perform a variety of tasks, but it is essentially used to search for specific data by filtering according to specific criteria. Queries can also automate many management tasks, summarize data, and perform calculations.

In addition, queries can include many operations such as join tables, crosstabs, deletes, create tables, parameters, aggregates, and updates. A query parameter allows users to run variations of a specific query, asking users to enter field values ​​and using those values ​​to create search criteria. Meanwhile, a rollup query helps users group and summarize data for easy analysis.

In SQL relational databases, data is stored as records (or rows of information). An SQL SELECT query allows users to select and return data from the database to the application. The results of a query are stored in a table called a “result set”. Users can use the SELECT statement with components such as FROM, WHERE, and ORDER BY to detail the query request. SQL SELECT queries can also group and aggregate data for analysis or summarization.

To make it easier to understand, the query process can be compared to ordering a cup of coffee at a coffee shop. When a customer requests a cup of coffee, the barista understands the request and provides the correct service. Queries work in a similar way: the user requests information, and the database system understands and returns the requested results.

The query code for a particular request is a common code used across query languages, allowing users and databases to communicate easily because they both “speak” the same language. However, queries are not only performed using query languages. For example, users can also perform queries through available parameters, which increases flexibility when requesting data.

Database Query Tools

Query Folding

Query folding is a key feature in Power Query, Microsoft's data transformation and aggregation tool. For SQL and NoSQL data sources such as Active Directory, OData, or Exchange, Power Query uses the aggregation engine to convert data from M Language (Power Query's data transformation language) into a language the data source can understand, usually SQL.

When performing complex calculations and transformations, Power Query uses query folding to push these tasks directly to the data source, thereby optimizing efficiency and saving resources. This tool is developed to handle large volumes of data efficiently. Power Query tries to perform query folding whenever possible to improve performance.

Power BI, Microsoft's business intelligence platform, integrates with Power Query, allowing users to perform hundreds of different data transformations and participate in query folding. Power BI provides powerful tools for aggregating, analyzing, visualizing, and sharing data, creating an optimal ecosystem for data management.

Web Search Queries

Web search queries describe the keywords or sentences that users enter into search engines such as Bing, Google, or Yahoo. Unlike SQL queries, web search queries do not require location parameters or specific keywords. Instead, they request information about a specific topic.

Search engines use algorithms to find and return the most accurate results based on user requests. Search results are sorted by importance and relevance, in order to provide the most accurate information.

Web search queries can be divided into three main types:

• Navigational search: Searches aimed at finding a specific website.
• Informational search: Searches to cover a broad topic.
• Transactional Search: Searches that are intended to complete a transaction, such as online shopping.

Other Query Types

In addition to SQL queries and web searches, there are other types of queries such as querySelector() in JavaScript and query errors on platforms like Facebook.

querySelector() in JavaScript: This function helps users search for elements on a web page that satisfy certain conditions using a CSS selector chain. The querySelectorAll() method is also used to return all matching elements. If the selector is invalid, the system returns a SyntaxError exception, and if no elements match, the function returns a null value.

Facebook Query Error: When encountering problems with a query on Facebook, users may receive an error message such as "Error while executing query". This error can be resolved by refreshing the page, logging out and logging back in, or clearing cache and cookies.

Databases play an important role in building and operating applications, storing data and helping applications operate normally. Database queries are basic tools that help users request, retrieve and control information easily from the database system. Contact Intech Group now for more in-depth advice and support on how to use data in many different situations, especially in the current era of data explosion.

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