This document provides an overview of SQL, including: 1) SQL is a language used to work with databases in the "back end" and is not typically part of the user interface. 2) SQL standards were set in 1986 and allow for different levels of conformance between vendor implementations. 3) SQL is declarative rather than procedural, with code describing results rather than tasks, though it includes some procedural elements.

1. SQL Overview
CIS-182

2. Structured Query Language
• Language used to work with databases
• Used in „back end‟
– Typically not part of user interface (don‟t expect users
to type in a query…)

3. SEQEL to SQL
• Structured English Query Language developed
by IBM
• Other companies developed similar products
• ANSI set standards in 1986
– Standards are „open‟
– Different vendors have different levels of
conformance

4. SQL
• Most languages are procedural
– Describe how to perform a task
• SQL is non-procedural (declarative)
– Code describes results
– Includes some procedural components
• If … Then, Loops
• Database apps typically use both types of
languages
– Procedural languages manage interface, data requests
– SQL manages data storage and retrieval

5. Types of SQL Statements
• Data Definition Language (DDL): Create/edit
objects
– CREATE, ALTER
• Data Control Language (DCL): Specify access
and permissions
– GRANT, REVOKE
• Data Manipulation Language (DML): Work with
data
– SELECT * FROM Employees
– INSERT INTO Students

6. Logical Organization
• Catalogs: group of schemas
• Schema: group of related tables, views
• Implementation is up to vendor
– Some vendors use catalogs, some don‟t
– Vendors have different levels of support for schemas

7. Databases
• „Database‟ is not an ANSI specification
• Most vendors have a database object
• In practice, schema and database tend to be
viewed interchangeably
– Schema defines the contents of a database
– May have sub-schemas to reflect application needs
(include only a portion of the database)

8. Coding
• One command may extend across several lines
– [Enter] doesn‟t represent the end of a statement
– SQL uses ; (semi-colon) to identify statement end
• ; is optional in SQL Server
• Keywords are capitalized
– CREATE DATABASE MyNewDatabase
• No standard conventions for naming
– Typically use Pascal case naming with each new
word capitalized

9. Naming Requirements
• Object names are not typically case sensitive
– Delimited identifiers wrap names in double quotes
and ARE case sensitive
– “MyNewTable” uses double quotes to identify the
object name
– Single quotes identify strings (text)
• Can use letters, numbers, underscore
– Can‟t use spaces, punctuation

10. Qualified Names
• A qualified name defines explicitly how to find
an object
– „.‟ is used as separator
• SQL Server uses
ServerName.DatabaseName.OwnerName.ObjectName
OR
ServerName.DatabaseName.SchemaName.ObjectName

11. Coding Reference
• SQL Server uses special characters to identify
different parts of commands
• End of statement: ;
– Optional in SQL Server
• Placeholder: <>
• Placeholder Definition: ::=
• Optional Parameter(s): [ ]
• Specific Parameter Values: { }
• Value Separator: |
• List Separator: ,

12. Placeholder Example
• Basic command definition:
ON UPDATE <referential action>
<referential action> ::= CASCADE|SET NULL
<referential action> is placeholder
CASCADE|SET NULL is placeholder definition
(placeholder value must be one of these choices)

13. Management Studio
• Microsoft GUI for most SQL Server operations
– Additional applications manage overall server
security, business intelligence
• Separate application from SQL Server
– Uses a connection to send commands and capture
results
– SQL Server is not something we‟ll work with directly