Sql Cheat Sheet
* MS SQL Server is a Relational Database Management System developed by Microsoft Inc. * Its primary query languages are: T-SQL, ANSI SQL. * Oracle * Excellent database server choice for client/server computing. * Very large and multi-user database management system.
1. Microsoft Access is entry-level database management software. 2. RDBMS stands for Relational Database Management System. * Basis for SQL, and for all modern database systems * Based on the relational model as introduced by E. F. Codd.
1. The data in RDBMS is stored in database objects called tables. * Most common and simplest form of data storage * NULL value in a table is a value in a field that appears to be blank * Broken up into smaller entities called fields. 2. Constraints are the rules enforced on data columns on table. * ensures the accuracy and reliability * Column level constraints are applied only to one column * Table level constraints are applied to the whole table. * NOT NULL Constraint: Ensures that a column cannot have NULL value. * DEFAULT Constraint : Provides a default value for a column when none is specified. * UNIQUE Constraint: Ensures that all values in a column are different. * PRIMARY Key: Uniquely identified each rows/records in a database table. * FOREIGN Key: Uniquely identified a rows/records in any another database table. * CHECK Constraint: The CHECK constraint ensures that all values in a column satisfy certain conditions. * INDEX: Use to create and retrieve data from the database very quickly.
NOT NULL Constraint * Represents unknown data.
* For example, the following SQL creates a new table called CUSTOMERS and adds five columns, three of which, ID and NAME and AGE, specify not to accept NULLs:
DEFAULT Constraint * provides a default value to a column * For example, the following SQL creates a new table called CUSTOMERS and
1. Microsoft Access is entry-level database management software. 2. RDBMS stands for Relational Database Management System. * Basis for SQL, and for all modern database systems * Based on the relational model as introduced by E. F. Codd.
1. The data in RDBMS is stored in database objects called tables. * Most common and simplest form of data storage * NULL value in a table is a value in a field that appears to be blank * Broken up into smaller entities called fields. 2. Constraints are the rules enforced on data columns on table. * ensures the accuracy and reliability * Column level constraints are applied only to one column * Table level constraints are applied to the whole table. * NOT NULL Constraint: Ensures that a column cannot have NULL value. * DEFAULT Constraint : Provides a default value for a column when none is specified. * UNIQUE Constraint: Ensures that all values in a column are different. * PRIMARY Key: Uniquely identified each rows/records in a database table. * FOREIGN Key: Uniquely identified a rows/records in any another database table. * CHECK Constraint: The CHECK constraint ensures that all values in a column satisfy certain conditions. * INDEX: Use to create and retrieve data from the database very quickly.
NOT NULL Constraint * Represents unknown data.
* For example, the following SQL creates a new table called CUSTOMERS and adds five columns, three of which, ID and NAME and AGE, specify not to accept NULLs:
DEFAULT Constraint * provides a default value to a column * For example, the following SQL creates a new table called CUSTOMERS and