SQLsatsen

SQLsatsen, or SQL statement, is a single instruction written in the SQL language used to interact with a relational database. A statement can query data, modify data, or alter the database schema. SQL statements are issued to a database management system (DBMS) such as MySQL, PostgreSQL, Oracle, or SQL Server, which parses, optimizes, and executes them. SQL statements are categorized into data manipulation language (DML), data definition language (DDL), data control language (DCL), and transaction control language (TCL). Typical DML statements include SELECT, INSERT, UPDATE, and DELETE. DDL includes CREATE, ALTER, and DROP. DCL includes GRANT and REVOKE. TCL includes COMMIT, ROLLBACK, and SAVEPOINT.

Common syntax basics: a SELECT statement can include a SELECT list, FROM clause, WHERE filter, and optional GROUP BY, HAVING, and ORDER BY clauses. For example: SELECT name, email FROM customers WHERE country = 'Sweden'; or INSERT INTO orders (customer_id, amount) VALUES (123, 45.50).

Standards and implementation: SQL is standardized by ISO/IEC 9075, with vendor-specific extensions. Most DBMSs support core SQL with variations and proprietary features, which can affect syntax and available functions.

Security and best practices: use parameterized or prepared statements to avoid SQL injection; validate and escape inputs; use transactions for atomicity; handle errors gracefully. History: SQL originated in the 1970s at IBM and was standardized in the following decades, leading to widespread adoption across relational databases.