Category: SQL Faqs

An SQL view is essentially a virtual table that derives its data from the outcome of a SELECT query. Views serve multiple purposes, including simplifying intricate queries, enhancing data security through an added layer, and enabling the presentation of targeted data subsets to users, all while keeping the underlying table structure hidden.

The WHERE clause is employed to restrict individual rows before they are grouped, such as when filtering rows prior to a GROUP BY operation. Conversely, the HAVING clause is utilized to filter groups of rows after they have been grouped, like filtering groups based on aggregate values.

The ORDER BY clause is used to sort the result set of a query based on one or more columns. You can specify each column’s sorting order (ascending or descending). For example: SELECT * FROM products ORDER BY price DESC;

An SQL alias serves as a transitory label bestowed upon either a table or a column within a query, with the primary purpose of enhancing the clarity of query outcomes or simplifying the process of renaming columns for improved referencing. For example: SELECT first_name AS “First Name”, last_name AS “Last Name” FROM employees;

The GROUP BY clause organizes rows from a table into groups based on the values in one or more columns. It is commonly employed alongside aggregate functions like SUM, COUNT, AVG, MIN, and MAX to perform computations on data that has been grouped together.

Indexes improve the data retrieval operations speed. They provide a quick way to locate specific rows in a table by creating a sorted data structure based on one or more columns. Indexes are essential for optimizing query performance.

Normalization is the method used to streamline data storage within a database, reducing redundancy and enhancing data integrity. This approach entails dividing tables into more manageable, interrelated tables and establishing connections between them.

A constraint in SQL defines rules or restrictions that apply to data in a table, ensuring data integrity. Common constraints include:

The SELECT statement serves the purpose of fetching data from one or multiple tables, enabling you to specify the desired columns to retrieve, apply filters through the WHERE clause, and manage the result’s sorting using the ORDER BY clause.

In SQL, a table is a structured data collection organized into rows and columns. Each column in a table is called a field, representing a specific attribute or property of the data.