SQLlekérdezéseket

SQL lekérdezések, often referred to as SQL queries, are commands written in structured query language (SQL) used to retrieve, manipulate, and manage data stored in relational databases. These queries are the fundamental way users interact with a database, allowing them to extract specific information, update existing records, insert new data, or delete unwanted entries.

The most common type of SQL query is the SELECT statement. This command is used to fetch data from one or more tables. It allows for filtering records based on specific conditions using the WHERE clause, sorting the results with the ORDER BY clause, and joining data from multiple tables with JOIN operations. Other crucial SQL commands include INSERT for adding new rows, UPDATE for modifying existing data, and DELETE for removing records.

SQL is a declarative language, meaning users specify what data they want, and the database management system (DBMS) figures out the most efficient way to retrieve or modify it. This abstraction makes SQL powerful and versatile, enabling complex data operations with relatively simple syntax. Understanding SQL queries is essential for anyone working with databases, from data analysts and developers to database administrators.