What is SQL (Structured Query Language)?
Turkish: SQL
SQL is the standard language for querying, changing, and reporting on structured data stored in relational database tables.
What is SQL?
SQL (Structured Query Language) is the query language used to read and change data stored in relational tables. A system can use SQL to find customers who ordered in the last 30 days, update stock quantities, or build a monthly sales report.
The core SQL statements are SELECT, INSERT, UPDATE, and DELETE. JOIN combines data from related tables, GROUP BY creates aggregates for reporting, and transactions make several changes succeed or roll back as one unit. Indexes can make reads much faster when designed well, but they also add cost to writes and storage.
Business Use
SQL is the common data language behind accounting, CRM, e-commerce, ERP, and reporting systems. PostgreSQL, MySQL, SQL Server, and Oracle differ in features, but the basic query model is shared across them.
In business applications, SQL is not only a developer tool. Finance teams rely on it for reconciliation, operations teams use it for inventory movement, and leadership teams read SQL-backed dashboards. Secure use depends on parameterized queries, careful permissions, backups, and regular review of slow or expensive queries.
Related Terms
ACID describes Atomicity, Consistency, Isolation, and Durability, the transaction guarantees that keep database writes reliable.
Connection PoolA connection pool keeps database or service connections open for reuse, lowering latency and connection overhead under traffic.
Database IndexingDatabase indexing creates auxiliary data structures on selected columns so queries find rows faster without scanning every record.
Database TransactionA database transaction groups reads and writes into one unit of work that either commits completely or rolls back safely.
ERD (Entity-Relationship Diagram)An ERD visualizes database entities, attributes, and relationships so teams can understand and review data model decisions.
Foreign KeyA foreign key links a value in one table to a key in another table, preserving referential integrity in relational databases.
Database IndexA database index stores selected columns in a separate data structure so queries can avoid scanning a table from start to finish.
Database MigrationDatabase migration applies table, column, index, and data transformation changes through versioned files in a controlled way.
MySQLMySQL is a relational database that stores SQL data in tables, indexes, and transactions, widely used behind web applications and services.
PostgreSQLPostgreSQL is an open-source ACID-compliant relational database that combines SQL, JSON support, indexing, and extensibility.