Sql Cheat Sheet

Topics: SQL, Relational model, Data modeling Pages: 3 (594 words) Published: June 29, 2013
* 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 adds five...
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