SQL Commands have subcategories like DDL, DML, DCL and TCL
DDL is defined as Data Definition Language : DDL is used to define data structures which deals with database descriptions.
CREATE: It helps to create database
ALTER : it helps to alter the pre-existing data
DROP: It helps to delete objects or data from the database
TRUNCATE: It remove all records from a table
COMMENT: It helps to add comments to the data dictionary.
RENAME : It helps to rename an object in the database
DML is defined by Data Manipulation Language to manipulate data itself with the following commands:
SELECT : it helps to retrieve data from one or more tables in the database
INSERT : it helps to insert data into a existing table
UPDATE : it helps to update existing data within a existing table
DELETE : it helps to delete all records from a table