Creating tables/Deleting tables/Altering tables/Column and table constraints

Adding/Dropping constraints

Constraints are added and dropped with the ALTER TABLE TableName followed by ADD, DROP, or CHANGE clause values

Constraint

A rule that governs allowable values in a database. Constraints are based on    relational and business rules and are implemented with special keywords in a  CREATED  TABLE statement. The database automatically rejects insert, update, and delete statement that violate a constraint

ALTER table

Adds, Deletes, or Modifies columns on an existing table

CREATE table

Creates a new table by specifying the table name, column names, and column data types. 
Example data types: INT/INTEGER, VARCHAR(N), DATE, and DECIMALS

DROP Table

Deletes a table, along with all the table's rows, from a database

Referential integrity

Every foreign key value must match an existing primary key value or be NULL