SQL Data Definition – Objects

This section provides an overview of the primary database objects that can be defined using SQL Data Definition Language (DDL) statements.

Tables

Tables store data in rows and columns. They are defined with CREATE TABLE and can include constraints such as primary keys, foreign keys, defaults, and checks.

DDL Statement	Description
`CREATE TABLE`	Creates a new table.
`ALTER TABLE`	Adds, modifies, or drops columns and constraints.
`DROP TABLE`	Removes a table and its data.

Views

Views are virtual tables defined by a query. They simplify complex queries and can provide security by restricting column access.

DDL Statement	Description
`CREATE VIEW`	Defines a new view.
`ALTER VIEW`	Modifies an existing view definition.
`DROP VIEW`	Deletes a view.

Indexes

Indexes improve query performance by providing fast access paths to rows. They can be clustered, non‑clustered, unique, or filtered.

DDL Statement	Description
`CREATE INDEX`	Creates a new index.
`CREATE UNIQUE INDEX`	Creates a unique index.
`DROP INDEX`	Removes an index.

Stored Procedures

Stored procedures encapsulate reusable T‑SQL logic. They can accept parameters, return result sets, and manage transactions.

DDL Statement	Description
`CREATE PROCEDURE`	Creates a new stored procedure.
`ALTER PROCEDURE`	Modifies an existing procedure.
`DROP PROCEDURE`	Deletes a procedure.

Functions

Functions return a scalar value or a table. They are deterministic and can be used in queries, constraints, and computed columns.

DDL Statement	Description
`CREATE FUNCTION`	Creates a new scalar or table‑valued function.
`ALTER FUNCTION`	Modifies an existing function.
`DROP FUNCTION`	Deletes a function.

For detailed syntax and examples, refer to the individual object pages linked in the left navigation.

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