test-sqldexter

SQL Query Categories:

• DDL – It stands for Data Definition Language. These statement used to define the structure of database and schema.
• CREATE – creates object in database
• DROP – deletes object from database
• ALTER – alters structure of database
• TRUNCATE – Removes all records from a table
• COMMENT – Add comment to data dictionary
• RENAME – rename an object in database.

• DML - Data Manipulation Language (DML) statements are used for data manipulation.
• INSERT – inserts data into a table
• SELECT – retrieve/fetch data from database
• UPDATE – update existing data within a table
• DELETE – deletes data from a table
• UPSERT – Update on duplicate else insert data into a table

? Why Truncate is a DDL statement while delete is DML although both achieve same result??

• DCL – Data Control Language (DCL) statements uses for control over data. It control access rights of users.
• GRANT – gives access permission to database
• REVOKE – withdraw access privilege given to user/users
• · TCL – Transaction Control Language(TCL) statement controls atomicity of the statements. It controls transaction.
• COMMIT –saves permanently into database.
• ROLLBACK – Restore database to its previous stable state
• SAVEPOINT – Identify a point to which transaction can be rolled back in case of any error/issue.
• START TRANSACTION – Indicates starting point of transaction

SQL stands for structured query language. SQL is a kind of programming language specially designed for managing relational database management system (RDBMS). It is based upon relational algebra and tuple relational calculus.

The concept of relational data model for databases and its characteristics was coined by Edgar F. Codd. He had proposed few guidelines/ rules that must be followed by a database in order to be said as relational database. Codd’s 12 rules was the pioneer in laying the foundation of relational data model for databases.

Kindly refer for codd’s rule in detail at http://en.wikipedia.org/wiki/Codd%27s_12_rules.

SQL and its Uses:

SQL is standard medium to communicate with database and get relevant information queried. SQL queries/statements can be broadly classified into following four categories:

• DDL

• DML

• DCL

• TCL