SQL Basics

I thought to write few posts about SQL and Database testing. This post is the result of that interest.

SQL - Structured Query Language. SQL is used to interact with databases. SQL is a non-procedural language and has few standards. SQL is standardized by the American National Standards Institute (ANSI).

Rules for writing SQL statements

• It is not case sensitive.
• It cannot be abbreviated or split across lines.
• It can be on one or more lines.
• Indents are used to enhance readability.
• Clauses are usually placed on separate lines.

SQL's Components / Sub Languages
SQL consists of few components and given below:

• DDL - Data Definition Language - Create, Alter, Drop, Truncate - For creating, altering and dropping the database objects like tables, viewes, indexes, synonyms,sequences and contraints.
• DML - Data Manipulation Language - Insert, Update, Delete - For reading and updating data.
• DRL - Data Retrieval Language - SELECT - For querying the data. SELECT has many clauses.
• TCL - Transaction Control Language - Commit, Rollback, SavePoint - These allow to group one or more DML statements into units of work or transactions. All statements in a transaction either succeed or fail as a single group.
• DCL - Data Control Language - Grant, Revoke - For managing database security, by creating user ids and assigning or removing privileges from them.