SQL

SQL (Structured Query Language) is used to manage data in a relational database management system.

Diagrams from ByteByteGo

Execution Order

SQL Components

Engineering relational databases required an understanding of the following components

• DDL: (data definition language)
  • syntax for creating and modifying database objects such as tables, indices, and users
  • e.g., CREATE, ALTER, DROP
• DQL: (data query language)
  • used for performing queries on the data within schema objects
  • e.g., SELECT
• DML: (data manipulation language)
  • used for adding (inserting), deleting, and modifying (updating) data
  • e.g., INSERT, UPDATE, DELETE
• DCL: (data control language)
  • used to control access to data stored in a database i.e., authorization
  • e.g., GRANT, REVOKE
• TCL: (transaction control language)
  • used to maintain the integrity and consistency of the data stored in the database
  • e.g., COMMIT, ROLLBACK

Types of Joins