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SQL: The Structured Query Language 13 * Introducing Structured Query Language * Discovering Access data types * Learning SQL's sub-languages * Operating on databases with SQL Stations Along the Way

Introducing Structured Query Language  Uses the acronym SQL (pronounced ess-que-ell)  Is supported (to some degree) by all modern relational databases  Contains three sub-languages  Interfaces directly with Access table data  Can connect to external data sources

SQL as an Action Language  Syntax: Specifies the order and spelling of words in SQL statements  Semantics: Imparts meaning  Commands: Demand action from a database  Keywords: Specify the action in a command

Data Types for SQL Statements In Access, column data types tell you… …the type of data in a column and …what you can do with it Define column data types for the data’s intended use

SQL Syntax Definitions Symbol / ConventionWhat It Does ALL CAPSIdentifies a keyword lowercaseIdentifies table and field names [ ] (square brackets)Enclose optional keywords... (ellipsis)Signifies continuation,... (comma + ellipsis)Marks multiple entries of one type { } (curly brackets)Contain alternative required options

SQL Sub-Languages Sub-LanguageCommon Keywords Data Definition Language (DDL) ALTER CREATE DROP Data Manipulation Language (DML) DELETE INSERT SELECT SELECT...INTO TRANSFORM UPDATE Data Control Language (DCL)GRANT REVOKE

Data Definition Language  Defines the database landscape  Creates database objects with CREATE: Tables Views Indexes  Deletes database objects with DROP  Modifies table structure with ALTER

Data Manipulation Language  Manipulates data in a database  Writes data to a table or tables with INSERT  Pulls data from a database with SELECT  Makes a new table from one or more tables with SELECT... INTO  Change or correct table data with UPDATE  Remove table data (not objects) with DELETE

Data Control Language  Supports user-level security for pre-2007 Access databases  Bestows user privileges with GRANT  Removes user privileges with REVOKE

Discussion Topics What is Structured Query Language? Is SQL really a language? Why does SQL have sub-languages?