IE 423 – Design of Decision Support Systems Database development – Relationships and Queries Introduction to SQL

Important Events Back from Spring Break (hopefully) Welcome Back

Keepin Up Read Pol and Ahuja – Chapter 8 (should have already done this) Pol and Ahuja – Chapter 9 – SQL Pol and Ahuja – Chapter 10 – Visual Studio

SQL SQL – Structured Query Language Standard language for managing and manipulating Relational Databases and Relational DataBase Management Systems RDBMS? Standard – because it is widely used in RDBMSs  …but not in all

SQL SQL – used in MS Access (behind the “curtain”) MS SQL Server Oracle DB2 MySQL PostGres …

SQL SQL – standard, but… Some variations in SQL across platforms Usually syntactic differences Function differences  Subsets  Arguments

SQL SQL – Important Point! SQL is a database management language SQL is not a programming language What does this mean? Why does this matter? What can we do about this?

SQL SQL – four components to the language DDL – Data Definition Language  Define/delete db objects DML – Data Manipulation Language  Language for using db DCL – Data Control Language  Defines/sets control features of db DSPL – Data Stored Procedure Language  Tools for creating SQL modules

SQL SQL – four components to the language DCL and DSPL – outside the scope of this class (mostly) DDL and DML – we will take a closer look at these two languages

SQL SQL – four components to the language DCL and DSPL – outside the scope of this class (mostly) DDL and DML – we will take a closer look at these two languages

DDL DDL – Data Definition Language Create  TABLES  PRIMARY KEYS  FOREIGN KEYS  INDEXES

DDL CREATE tables CREATE TABLE [tblName] ({ }, {},…) CONSTRAINT { PRIMARY KEY (fieldname1, fieldname2,…) {}… ;

DDL CREATE tables CREATE TABLE tblDepartment (DeptIDVARCHAR2 (10) NOT NULL, NameVARCHAR2 (20), Address VARCHAR2 (200), PhoneNUMBER (30), CollegeIDVARCHAR2(3) ) CONSTRAINT deptPK PRIMARY KEY (DeptID), deptFK FOREIGN KEY (CollegeID) REFERENCES tblCollege (CollegeID) ;

DDL CREATE tables Standard SQL datatypes  VARCHAR(maxbytes) -- TEXT same in MySQL Max maxbytes – Oracle = 4000; SQL Server=8000; MySQL=65,532 (see docs for specific DB platform  DECIMAL(precision, scale) (optional) Numeric base10 to a specific precision and scale (number of fractional decimal positions) DECIMAL(9,2) could store 9,999,  DATE (some variation across DB platforms) DATE TIME TIMESTAMP

DDL CREATE tables Standard SQL datatypes  SMALLINT 2 bytes -32,768 to 32,767  INTEGER 4 bytes -2,147,483,648 to a 2,147,483,647  BIGINT 8 bytes -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807

DDL CREATE Indexes CREATE INDEX tblDeptAddressIndex ON tblDepartment (Address) ;

DDL DDL – Data Definition Language DROP – deletes db objects DROP TABLE – deletes a table (and its data) from a db …not used to drop a field from a table or a record from a table

DDL DDL – Data Definition Language DROP TABLE [tblName];  DROP TABLE tblInstructors; DROP INDEX [tblNameindex]  DROP INDEX tblStudentIndex;

DDL DDL – Data Definition Language ALTER – modifies db objects Add a field to a table ALTER tblDepartment ADD COLUMN Chair Number (10) ADD CONSTRAINT deptFK2 FOREIGN KEY (Chair) REFERENCES tblFaculty(FacultyID) ;

DDL DDL – Data Definition Language ALTER – modifies db objects Delete a field from a table ALTER tblDepartment DROP Chair DROP CONSTRAINT DeptFK2 ;

DML DML – Data Manipulation Language Language to use DB Language to do queries and other DB functions Why do you need to know this?

DML Select Queries SELECT [fieldName, fieldName2,…] FROM [tblName]; SELECT Name, Phone FROM tblDept; SELECT * FROM tblStudent;

DML Select Queries - JOIN SELECT [fieldName, fieldName2,…] FROM [tblName1, tblName2, tblName3,…]; SELECT Name, , DeptName FROM tblFaculty tblDept; Simple Query with Join But what does this do?

DML Select Queries – JOIN SELECT Name, , DeptName FROM tblFaculty tblDept; Simple Query with Join But what does this do? Cartesian Product What’s that?

DML Select Queries – JOIN and the WHERE clause SELECT Name, , DeptName FROM tblFaculty tblDept WHERE tblFaculty.DeptID=tblDept.DeptID;

DML Select Queries – JOIN and the WHERE clause How about this – Name in tblFaculty, Name in tblDept SELECT Name, , Phone, Name FROM tblFaculty tblDept WHERE tblFaculty.DeptID=tblDept.DeptID; Two fields in query with same identifier? Oh my!

DML Select Queries – JOIN and the WHERE clause Use a qualifier – fully specify field name using its table name SELECT tblFaculty.Name, , Phone, tblDept.Name FROM tblFaculty tblDept WHERE tblFaculty.DeptID=tblDept.DeptID;

DML Select Queries – JOIN and the WHERE clause WHERE clause operators –  = >= !=  BETWEEN, LIKE, IN  AND, OR, NOT

DML Select Queries – JOIN and the WHERE clause SELECT Name, , Salary, StartDate, tblDept.Name FROM tblFaculty, tblDept WHERE tblFaculty.DeptID=tblDept.DeptID AND (Salary > 80000) AND (StartDate > #1/1/1995#);

DML Select Queries – JOIN and the WHERE clause BETWEEN – matching a range SELECT Name, , Salary, StartDate, tblDept.Name FROM tblFaculty, tblDept WHERE tblFaculty.DeptID=tblDept.DeptID AND (Salary BETWEEN AND 80000) AND (StartDate > #1/1/1995#);

DML Select Queries – JOIN and the WHERE clause BETWEEN – matching a range SELECT Name, , Salary, StartDate, tblDept.Name FROM tblFaculty, tblDept WHERE tblFaculty.DeptID=tblDept.DeptID AND (Salary BETWEEN AND 80000) AND (StartDate > #1/1/1995#);

DML Select Queries – JOIN and the WHERE clause LIKE – matching a string or part of one SELECT Name, , Rank FROM tblStudent, tblRegister, tblCourses WHERE (tblStudent.SID=tblRegister.StudentID) AND (tblRegister.CourseID=tblCourses.CourseID) AND (tblCourses.Cname LIKE “Cooking*” OR tblCourses.Cname LIKE “Food*” );

DML Select Queries – JOIN and the WHERE clause LIKE – matching a string or part of one LIKE match operators * - zero or more characters ? – zero or one character % - any number of characters ( %science% ) _ - any one character

DML Select Queries – JOIN and the WHERE clause Using aliases AS -- lets your rename objects  Within the query  Alias does not persist SELECT Name, , Rank FROM tblStudent AS tS, tblRegister AS tR, tblCourses AS tC WHERE (tS.SID=tR.StudentID) AND (tR.CourseID=tC.CourseID) AND (tC.Cname LIKE “Cooking*” OR tC.Cname LIKE “Food*” );

DML Select Queries – JOIN and the WHERE clause Using aliases AS -- lets your rename objects  Within the query  Alias does not persist SELECT CONCAT(FirstName,” “,LastName) AS FullName, , Rank FROM tblStudent;

DML Select Queries – JOIN and the WHERE clause Sometimes we only want one result per entity

DML Select Queries – JOIN and the WHERE clause Remember this? What would we get as a result?

DML Select Queries – JOIN and the WHERE clause Remember this? What would we get as a result? SELECT Name, , Rank FROM tblStudent AS tS, tblRegister AS tR, tblCourses AS tC WHERE (tS.SID IN SELECT DISTINCT StudentID FROM tR WHERE tR.CourseID IN SELECT CourseID FROM tC WHERE (tC.Cname LIKE “Cooking*” OR tC.Cname LIKE “Food*” );

DML Select Queries – JOIN and the WHERE clause The keywork DISTINCT causes only one record per criteria match to be returned SELECT Name, , Rank FROM tblStudent AS tS, tblRegister AS tR, tblCourses AS tC WHERE (tS.SID IN SELECT DISTINCT StudentID FROM tR WHERE tR.CourseID IN SELECT CourseID FROM tC WHERE (tC.Cname LIKE “Cooking*” OR tC.Cname LIKE “Food*” );

DML Select Queries – JOIN and the WHERE clause Did you notice something else new? The keyword IN SELECT Name, , Rank FROM tblStudent AS tS, tblRegister AS tR, tblCourses AS tC WHERE (tS.SID IN SELECT DISTINCT StudentID FROM tR WHERE tR.CourseID IN SELECT CourseID FROM tC WHERE (tC.Cname LIKE “Cooking*” OR tC.Cname LIKE “Food*” );

DML Select Queries – JOIN and the WHERE clause Did you notice something else new? The keyword IN  Allows you to nest queries in queries

DML Select Queries – Ordering the results Use the ORDER BY clause SELECT [fields] FROM [tables] WHERE [select_criteria] ORDER BY [field1 ;

DML Select Queries – Ordering the results Use the ORDER BY clause SELECT Name, , Phone, StartDate FROM tblFaculty ORDER BY StartDate ASC; SELECT Name, , Phone, StartDate FROM tblFaculty ORDER BY StartDate DESC, Name ASC;

DML Select Queries – Summarizing data – getting some stats The GROUP BY clause SELECT tblDept.Name, COUNT(tblStudent.SID) AS StudentCount), AVG(tblStudent.GPA) AS MeanGPA FROM tblStudent, tblDept WHERE tblStudent.DeptID = tblDept.DeptID AND (tblDept.College=“CEMR”) GROUP BY tblDept.Name;

DML Select Queries – Summarizing data – getting some stats The HAVING clause, like WHERE but for GROUP BY SELECT tblDept.Name, COUNT(tblStudent.SID) AS StudentCount), AVG(tblStudent.GPA) AS MeanGPA FROM tblStudent, tblDept WHERE tblStudent.DeptID = tblDept.DeptID AND (tblDept.College=“CEMR”) GROUP BY tblDept.Name HAVING COUNT(tblStudent.SID >25);

DML Action Queries INSERT Queries DELETE Queries UPDATE Queries

DML Action Queries INSERT Queries INSERT INTO [table] (field1, field2, …) Values(“value1”, value2,…);

DML Action Queries INSERT Queries INSERT INTO tblStudent (Name, Age, ) Values(“Bob Smith”, 21, Order is important Datatypes must match

DML Action Queries DELETE Queries Deletes records from a table DELETE FROM [table] WHERE [delete_criteria];

DML Action Queries DELETE Queries Deletes records from a table DELETE FROM tblStudent WHERE Rank=“Senior”;

DML Action Queries Update Queries UPDATE [table] SET [field=value, field=value, …] WHERE [update_criteria];

DML Action Queries Update Queries UPDATE tblFaculty SET Salary = Salary *1.01 WHERE StartDate < 1/1/1920;