SQL Overview Structured Query Language

Description  When Codd first described the theory of relational databases, he asserted that there should be a comprehensive language that would describe both the data and the meta data.  SQL has developed into that language

SQL Features  SQL does not come as a separate package  It is always a part of a Data Base Management system  SQL is a fourth generation language (meaning it is not procedural. You describe what you want to do not how to do it)

Standards  SQL is an ANSI standard  Most DBMS implement the 1992 standard, some are beginning to implement the 1999 standard  In addition to the standard SQL most DBMSs add their own commands and features SQL Server has T-SQL Oracle has PSQL

Three Uses  To define data (including setting indexes and user permissions)  To query data  To manipulate data

Data Definition  You can define all the data structures in a relational database with SQL CREATE TABLE tblCustomer ( CustomerID Integer Primary Key, CustomerLastName varchar(50), CustomerFirstName varchar(35) )

Data Query  You can retrieve any data or combination of the data from the database with SQL queries SELECT CustomerLastName, CustomerFirstname, OrderID, OrderDate FROM tblCustomer c INNER JOIN tblOrder o ON c.CustomerID=o.CustomerID WHERE c.CustomerID=5;

Data Manipulation  You can Insert, Update and Manipulate data with SQL UPDATE tblCustomer SET LastName=‘Smith’ WHERE CustomerID=7;