Intro to SQL CS-422 Dick Steflik

Structured Query Language Developed by C. Date for Relational Data Base Management Systems (RDBMS) Simple Declarative Language has no program control statements

SQL Two categories of commands Data Manipulation Commands deal with: RETRIEVING DATA MAINTAINING DATA ADDING, UPDATING, DELETING Data Definition Commands DEAL WITH: CREATING DATABASE OBJECTS (TABLES,VIEWS) Object organization and attributes

Data Model Database objects are modeled on the concept of a table (i.e. rows and columns) Each row is a single table object Columns are the attributes of that table A database is a collection of related tables

Referential Integrity Rules to insure that table data stays accurate and accessible rows in a table should be unique one column should contain no duplicate data primary key column values cannot contain repeating groups or arrays null is different than space and zero, 2 null values are not considered equal

Data Manipulation Commands Select - query and display data from a database Insert - a new row into a table Update - modify a column in a table Delete a row from a table

Select Select (column list) from (sources) where (conditions) order by (ocolumn list) column list - comma separated list of names of columns to be in output Ex. ssn , lastname , firstname,gpa can contain literals to be included in output Ex. Ssn,”~”,lastname,”~”,firstname sources - name(s) of table(s) to retrieve data from conditions (optional) - conditions for selections lastname like “S%” (lastname = “Steflik) and (firstname like “R%”) ocolumn list (optional)- list of columns that output should be ordered by Ex select * from student select lastname,fristname from student where gpa > 3.0 select lastname,firstname from student order by lastname,firstname

Select - joined tables Two tables may be joined and viewed as a single data source is the both have a common column suppose we have 2 tables: Inventory and category and each has a column called catg_code In category catg_code is unique and is the primary key

Select - joined tables (cont.) Inventory Category P_no Catg_code qty Catg_code descr

Select - joined tables (cont.) To retrieve all of the part numbers and the name of the category to which the part belongs: select inventory.p_no category.descr from inventroy , category select a.p_no,” “,b.descr from a inventory , b category

Insert Add a row to a table use jdbc execute Update method insert into category values(“IGN”,”Ignition System”) use jdbc execute Update method ex. Stmt.executeUpdate(“insert into Category values(‘IGN’,’Ignition System’)”);

Update Modify an existing row in a table Use jdbc executeUpdate method update category set descr = “Ignition Subsystem” where catg_code = “IGN” Use jdbc executeUpdate method String s = “update category set descr = ‘Ignition Subsystem’ where catg_code = ‘IGN’ ”; stmt.executeUpdate(s);

Delete Remove a row from a table delete from category where catg_code = “IGN” remove the IGN category delete from category where catg_code like “I%” remove all rows where catg_code starts with an “I”

Data Definition Commands Create table add a table to a database Drop Table remove a table from a database Alter Table add or delete column(s)

A good reference Phil Greenspun – SQL for Web Nerds http://philip.greenspun.com/sql/