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Enterprise Development Using Visual Basic 6.0 Autumn 2002 Tirgul #8

Enterprise Development Using Visual Basic 6.0 Autumn 2002 Tirgul #8. Objectives. SQL Queries & Statements Useful SQL techniques DB Comparison. retrieve All records. SELECT * FROM Users Use Constants: Use inside Function:. Public Const GET_ALL_USERS = "Select * From Users".

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Enterprise Development Using Visual Basic 6.0 Autumn 2002 Tirgul #8

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  1. Enterprise Development Using Visual Basic 6.0 Autumn 2002Tirgul #8 ‘Tirgul’ # 8

  2. Objectives • SQL Queries & Statements • Useful SQL techniques • DB Comparison ‘Tirgul’ # 8

  3. retrieve All records • SELECT * FROM Users • Use Constants: • Use inside Function: PublicConst GET_ALL_USERS = "Select * From Users" PublicFunction GetAllUsers() As ADODB.Recordset '... Set RS = Connection.execute(GET_ALL_USERS) '... EndFunction ‘Tirgul’ # 8

  4. retrieve Some fields • SELECT UserID, UserName FROM Users • Use Constants: • Inside a function Public Const GET_USERS_FIELDS = "Select UserID, UserName” & _ “ From Users" Public Function GetUsersFields() As ADODB.Recordset '... Set RS = Connection.execute(GET_USERS_FIELDS) '... End Function ‘Tirgul’ # 8

  5. Conditions • SELECT UserID, UserName FROM Users WHERE UserName = 'James‘ • SELECT UserID, UserName FROM Users WHERE UserID < 10 • SELECT UserID, UserName FROM Users WHERE UserID < 10 OR UserName = 'James' ‘Tirgul’ # 8

  6. Conditions • Cannot build all string • Use inside Function: Public ConstGET_USER_BY_NAME = "SELECT UserID, UserName FROM Users WHERE UserName = '" Public Function GetUserByName(strUserName As String) As ADODB.Recordset '... Dim strQuery AsString strQuery = GET_USER_BY_NAME & strName & "'" Set RS = Connection.execute(strQuery) '... End Function ‘Tirgul’ # 8

  7. Sorting • SELECT * FROM Users ORDERBY UserName DESC • SELECT * FROM Users ORDERBY UserName • SELECT * FROM Users ORDERBY UserName ASC • SELECT * FROM Users ORDERBY UserName, UserID DESC ‘Tirgul’ # 8

  8. Sorting • Use Constants: • Use inside Function: PublicConst GET_USERS_ORDER_DESC = "SELECT * FROM Users ORDER BY UserName DESC" PublicFunction GetUserOrderDesc() As ADODB.Recordset '... Set RS = Connection.execute(GET_USERS_ORDER_DESC) '... EndFunction ‘Tirgul’ # 8

  9. Add records • INSERTINTO Users VALUES (10, 'James Crowley', 'PASSWORD') • INSERTINTO Users (UserName, UserID) VALUES ('James Crowley', 10) • INSERTINTO Users (UserName, Password) VALUES ('James Crowley', 'PASSWORD') ‘Tirgul’ # 8

  10. Add records Little an Evil.. • Use Constants: • Use inside Function: PublicConst INSERT_USER = "INSERT INTO Users (UserID,” & _ UserName)VALUES (‘" No Return value PublicFunction InsertUser(strUserID As String, _ strUserName As String) '... Dim strQuery AsString strQuery = INSERT_USER & strUserID & "'" & strUserName & "')" Set RS = Connection.execute(strQuery) '... EndFunction ‘Tirgul’ # 8

  11. Another option. • Use Array: PublicFunction InsertUser(UserDataArr) '... Dim strQuery AsString strQuery = INSERT_USER & UserDataArr(0) & "'" & UserDataArr(0) & "')" Connection.execute(strQuery) '... EndFunction PublicFunction InsertUser(UserDataArr) '... RS!UserID = UserDataArr(0) RS!UserName = UserDataArr(1) '... EndFunction ‘Tirgul’ # 8

  12. Updaterecords • UPDATE Users SET UserName = 'James Smith', Password = 'NEWPASSWORD' WHERE UserID = 10 • UPDATE Furniture SET Price = 10 WHERE ItemType = 'Cupboard' ‘Tirgul’ # 8

  13. Updaterecords • Use Constants: • Use inside Function: PublicConst UPDATE_USER = "UPDATE Users SET UserName = ‘" PublicFunction UpdateUser(strUserName As String) '... Dim strQuery AsString strQuery = UPDATE_USER & strUserName & "'" Connection.execute(strQuery) '... EndFunction ‘Tirgul’ # 8

  14. Delete a record • DELETEFROM Users WHERE UserID = 10 • DELETEFROM Furniture WHERE Price < 10 • TRUNCATETABLEauthors TRUNCATE TABLE is faster and uses fewer system and transaction log resources than DELETE ‘Tirgul’ # 8

  15. SQL Transaction statements • BEGIN TRANSACTION • COMMIT TRANSACTION • ROLLBACK TRANSACTION ‘Tirgul’ # 8

  16. Transaction Use PublicFunction Insert() AsBoolean Conn.BeginTrans 'Add 'Delete 'Update If Err.Number <> 0 Then Conn.RollBack Insert = False ExitFunction EndIf Conn.Commit EndFunction ‘Tirgul’ # 8

  17. Commercial Databases • Access • Simple yet useful • For a single/double work stations • Limit data size • MS SQL Server • Very common • Only Microsoft… • Ease of use • Time-to-market • Oracle • More “Commercial” • Known as a powerful tool • Multi platform – Win/Unix/Linux • IBM DB2 • More “Commercial” • Multi platform – Win/Unix/Linux • Useful for IBM family & tools ‘Tirgul’ # 8

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