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.
