• DDL: Data Definition Language, SQL for creating, changing, or deleting database structures.
    • CREATE: Creates database objects such as tables and indexes.
    • ALTER: Changes the structure of a database object, such as adding a column to an existing table.
    • DROP: Deletes a database object itself, such as a table. Dropping a table also deletes the data it contains.
    • TRUNCATE: Removes all rows while keeping the table structure. You cannot use WHERE to select specific rows to remove.
  • DML: Data Manipulation Language, SQL for adding, updating, or deleting data in a database.
    • INSERT: Adds new rows to a table.
    • UPDATE: Modifies values in existing rows. You can specify which rows to update with WHERE; omitting it targets all rows.
    • DELETE: Deletes rows from a table. You can specify which rows to delete with WHERE; omitting it targets all rows. The table structure is preserved.
  • DQL: Data Query Language, SQL for querying data. However, SELECT is sometimes included in DML.
    • SELECT: Queries data. It can select the columns you need, filter rows by conditions, join multiple tables, or aggregate data.
  • SQL (Structured Query Language) is a language for working with database structures and data, and DDL, DML, DQL, and other categories classify SQL commands by purpose.