VB for applications

Lesson Plan Fundamentals of VB VB for handling events in Access

Project 1 (parts 1-2-3) Avg = (27 submissions)

Visual Basic in Access Previous version (< 2002) –Use macro to perform automation –Use VB This version - Very little support for macro (only for backward compatibility) - Focus on VB

Visual Basic in Access VB is a real programming language and is NOT a macro language We focus on using VB for handling user-initiated events (keyboard press, mouse lick..) Where do we use Visual Basic for Applications code? –Docmd command –Write query expression –To create user-defined functions –Even handling, error handling …

Modules Form modules: –Contain code in response to event- triggered by a user using controls of a form Report modules –Contain code in response t event-trigged by reports, sections of reports Access modules, and Class modules –Allows you to define custom objects

Modules One or more procedures (sub-procedures) Example: Private Sub Add_Click() On Error GoTo Err_Add_Click ‘Start procedure code DoCmd.GoToRecord,, acNewRec Exit_Add_Click: ……. ‘End procedure code End Sub

Procedures Definition: private/public SUB ‘ code right here end SUB Similar to void-returned method in Java/C++ (or void returned functions in C)

Functions Functions: private/public FUNCTION ([Parameter as Datatype]) As ReturnType ‘ code right here end Function Similar to non-void-returned method in Java/C++ (or non- void returned functions in C)

Datatype Symbol value: type-declaration character Byte: [0,255] Symbol value: none Integer: [-2 31, ] Symbol value: % Boolean: true, false. Symbol value: none Long: [-2,147,483,648; 2,147,483,647] Symbol value: & Double: Symbol value: # Currency: symbol String: symbol value $ Date: symbol value none

Variables and naming conventions Implicit variables: IntegerVar% = 1234 Explicit variables: Dim IntegerVar As Integer

Variables Arrays: are variables that consists of a collection of values Dim newArray(20) as String ‘create an array with 21 elements indexed from 0 to 20 Dim newArray(1 to 20) as String ‘create an array with 20 elements indexed from 1 to 20

Controlling program flow Conditional statements: If boolean_expression1 then statement to be executed if boolean_expression1 is true Else statement to be executed if boolean_expression1 is false Endif

Controlling program flow Select case statement: Select Case case exp1 statement being executed if the value of variable name = exp1 case exp2 statement being executed if the value of variable name = exp2 …case else: statement being executed if none of the above is met End Select

Controlling program flow Case expression can be: single value or list of values range of values expression with relational operators Example: select case inputStr case “A” to “Z” char = “Upper Case” case “a” to “z” char =“Lower Case”

Repetitive commands For, Next For counter=startValue to stopValue Step stepValue ‘Code are here Next Example: Sum%=0 For i = 1 to 100 step 2 Sum%= Sum%+ i next i

Repetitive commands On Error GoTO Label GoTo label: creates a loop but breaks the structure of a program

VBA for event handling in Access Form -An event: mouse click, mouse movement, keyboard press -VBA code is used to process the actions associated with such an event. -Event procedure from properties for any controls in a form

Adding a button to open a new form

Private Sub Login_Click() On Error GoTo Err_OpenNewUserForm_Click Dim formName As String Dim formCriteria As String formName = "NewUser" DoCmd.OpenForm formName,,, formCriteria Exit_Err_OpenNewUserForm_Click: Exit Sub Err_OpenNewUserForm_Click: MsgBox Err.Description Resume Exit_Err_OpenNewUserForm_Click End Sub

Adding a button to display a specific record on another form

Private Sub DisplayUserInfo_Click() On Error GoTo Err_DisplayUserInfo_Click Dim stDocName As String Dim stLinkCriteria As String stDocName = "UserInformation" stLinkCriteria = "[FirstName]=" & "'" & Me![userfirstname] & "'" DoCmd.OpenForm stDocName,,, stLinkCriteria Exit_DisplayUserInfo_Click: Exit Sub Err_DisplayUserInfo_Click: MsgBox Err.Description Resume Exit_DisplayUserInfo_Click End Sub

Adding a button to display a specific record on another form

Private Sub DisplayUserInfo_Click() On Error GoTo Err_DisplayUserInfo_Click Dim stDocName As String Dim stLinkCriteria As String stDocName = "UserInformation" stLinkCriteria = "[FirstName] LIKE " & "'" & Me![userfirstname] & "'" DoCmd.OpenForm stDocName,,, stLinkCriteria Exit_DisplayUserInfo_Click: Exit Sub Err_DisplayUserInfo_Click: MsgBox Err.Description Resume Exit_DisplayUserInfo_Click End Sub

Referring to Access Object with VBA Form and form property: Example: Forms!UserInformation Forms!UserInformation.RecordSource Me.RecordSource Me.Userpassword

Validating data

Private Sub ISBN_BeforeUpdate(Cancel As Integer) If IsNull(Me!ISBN) Then MsgBox "This should not be empty" Exit Sub End If firstChar$ = Left(Me!ISBN, 1) Select Case firstChar$ Case 0 To 9 Exit Sub Case Else MsgBox “ISBN should start with a number" Cancel = True End Select End Sub

Practice Work on project 1 – part 5-6

Review for Exam Week 1: Three separate types of functionality: –Data Management –Application logic –Presentation Single-tier, client-server, three-tier architecture How Do Databases Support the World Wide Web

Review for Exam Week 2 Relational model: table, key(PR,FK), row, column, domain,tuple/record, NULL value Data integrity, entity integrity, Referential Integrity, enterprise integrity Views, relationship (three types, how to model them)

Review for Exam Week 3 Normalization Validating data (field level, table level) SQL statements

Review for midterm exam Week 4: Query: boolean expressions, different types of queries (select,action, parameter, crosstab) Different types of joins (equ(inner)joins, left/right joins)

Review for midterm exam Week 5 and week 6: Form and report

Review for midterm exam 1.Matching A-3 B-6 C-4 D-2 E-5 F-1

Review for midterm exam 2.Query operations on a database are very important. Which operation is not a query operation? a. Insert b. Update c. Select d. Model

Review for midterm exam 3. Consider a database with a logical description Employee (employeeNumber, lastName, firstName, age). Select the entry that would most likely be require to be unique a. employeeNumber b. lastName c. firstName d. Age e. None of the above

Review for midterm exam 4. Insert into video (videoId, movieName,typeDVDVHS) values (102, ‘Citizen Kane’,’VHS’); Insert into video (videoId, movieName,typeDVDVHS) values(103, ‘Chicago’,’DVD’);

Review for midterm exam 5. Employee table: Empid: Primary key (PK) State: Foreign key (FK) State table: Stateid: primary key(PK) Relationship between state and employee: one to many State: parent table Employee: child table

Review for midterm exam 5.2. SELECT Employee.Empid, Employee.Salary,Employee.Startdate, State.abbr FROM State INNER JOIN Employee ON State.Stateid=Employee.State WHERE State.abbr='WI';

Review for midterm exam 5.2. SELECT Employee.Empid, Employee.Salary, State.abbr FROM State INNER JOIN Employee ON State.Stateid=Employee.State WHERE Employee.StartDate < #1/1/2004#;

Review for midterm exam 5.4. SELECT STATE, COUNT(EMPID) as TotalEmployee, SUM(SALARY) as TotalSalary FROM EMPLOYEE GROUP BY STATE STATETotalEmployeeTotalSalary

Review for midterm exam Result EMPIDSALARYABBR CT CT NY NY NV WI SELECT EMPLOYEE.EMPID, EMPLOYEE.SALARY, STATE.ABBR FROM EMPLOYEE, STATE WHERE EMPLOYEE.STATE = STATE.STATEID

Review for midterm exam Result EMPIDABBR 00002CT 00005CT 00001NY 00003NY 00004NV 00006WI MD SELECT EMPLOYEE.EMPID, STATE.ABBR FROM STATE LEFT JOIN EMPLOYEE ON EMPLOYEE.STATE = STATE.STATEID

Review for midterm exam Result TotalSalary SELECT SUM(SALARY) FROM EMPLOYEE WHERE STARTDATE > #1/1/2004#

Review for midterm exam Result SALARYSTARTDATE /8/ /20/2003 SELECT SALARY, STARTDATE FROM EMPLOYEE WHERE STATE = (SELECT STATEID FROM STATE WHERE ABBR=”CT”)