Computer Programming Concepts and Visual Basic David I. Schneider

346 Computer Programming Concepts and Visual Basic
3. To view an existing record, use the navigator buttons (identical to those of the
data control) or the Find button to move to a record of a specified value.
4. To remove the current record from the table, click the Delete button. The record
is immediately deleted and cannot be recovered.
5. To edit an existing record, make changes in the data and click on the Update
button.
6. Press the Close button to return to the Database window.
At any time, the main section of the Database window contains a list of the
tables you have specified. Initially the main section is blank except for Properties.
(This is a list of properties pertaining to the database.) If you click the right
mouse button while highlighting a table, a menu will appear with the following
options:
Menu Item Use
Open Open the table to allow records to be added.
Design Specify the design (number and types of fields).
Rename Rename the given table.
Delete Remove the given table from the database.
Copy Structure Copies the structure of the given database with or without the data currently
contained in the database.
Refresh List Redisplay the list in the Database window.
New Table Open the Table Structure window.
New Query Open the Query Builder window.
■ CREATING A DATABASE IN CODE
The following lines of code create a database named “DBNAME.MDB” with two tables,
TABLE1 and TABLE2. TABLE1 has the fields FIELD1A (type Text with maximum length 50)
and FIELD1B (numeric of type Single). TABLE2 has analogous fields called FIELD2A and
FIELD2B, and also FIELD2C of type Integer. FIELD1A is a primary key of TABLE1 and
FIELD2A is a foreign key in TABLE2 referring to FIELD1A of TABLE1. FIELD2C is a primary
key of TABLE2. The record (“alpha”, 1997) is placed in TABLE1 and the record (“alpha”,
2000, 1) is placed in TABLE2. This code, which is contained in the file CREATEDB.TXT accompanying
this textbook, is intended as a template that you can modify to create a database
programmatically. (Note: The code can be placed into an event procedure. Before you run the
program, click on References in the Project menu and make sure that “DAO 3.51 Object
Library” is selected.)
Dim MyDB As Database, MyWs As Workspace
Dim T1, T2 As TableDef
Dim T1Flds(1 To 2), T2Flds(1 To 3) As Field
Dim TempFld As Field
Dim T1Idx, T2Idx As Index
Dim Rel As Relation
Dim MyRec As Recordset
’Create Database
Set MyWs = DBEngine.Workspaces(0)
Set MyDB = MyWs.
CreateDatabase(“C:\DBNAME.MDB”, dbLangGeneral)’Create first Table, TABLE1
Set T1 = MyDB.CreateTableDef(“TABLE1”)
’Specify fields for TABLE1
’Note the use of the optional parameter 50 for field size
’If 50 is omitted, the size will default to 20
Set T1Flds(1) = T1.CreateField(“FIELD1A”, dbText, 50)
Set T1Flds(2) = T1.CreateField(“FIELD1B”, dbSingle)
’Add the New fields to the field list in the Table