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Virtual Table and DataGridView

Virtual Table and DataGridView. Virtual Table DataGridView. Virtual Tables. SQL statements create a new “virtual” table from existing tables. Think of the following statement as creating a "virtual table" SELECT city, pop2015 FROM Cities WHERE pop2015>=20 Results in:.

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Virtual Table and DataGridView

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  1. Virtual Table and DataGridView • Virtual Table • DataGridView Ch. 10

  2. Virtual Tables • SQL statements create a new “virtual” table from existing tables. • Think of the following statement as creating a "virtual table" SELECT city, pop2015 FROM Cities WHERE pop2015>=20 • Results in: city pop2015Bombay 22.6Delhi 20.9 Mexico City 20.6 Sao Paulo 20.0Tokyo 36.2 Ch. 10

  3. Another Virtual Table SELECT * FROM Countries WHERE country Like 'I%' ORDER BY pop2005 ASC • Results in: country pop2005 monetaryUnit Indonesia 222.8 rupiahIndia 1103.4 rupee Ch. 10

  4. Views • “Virtual” tables don’t exist physically. • For all practical purposes, Visual Basic acts as if they did. • You may also see a “virtual” table called a view. Ch. 10

  5. The DataGridView Control • The DataGridView displays the values for an entire view in a table format similar to the table displayed by Database Explorer. • The prefix for the name of a DataGridView control is dgv. • After a data table has been filled, the statement dgvDisplay.DataSource = dt displays the contents of the data table dt in the data grid. Ch. 10

  6. Lab sheet 10.5: Form dgvDisplay Ch. 10

  7. Lab sheet 10.5: Code Private SubfrmCities_Load(...) Handles MyBase.Load UpdateGrid("Select * From Cities") End Sub Private SubbtnOrderbyPop_Click(...) HandlesbtnOrderbyPop.Click UpdateGrid("Select * From Cities Order By pop2005 ASC") End Sub Private SubbtnShowMonUnit_Click(...) _ HandlesbtnShowMonUnit.Click UpdateGrid("SELECT city, Cities.country, " & _ "Cities.pop1995, monetaryUnit " & _ "FROM Cities INNER JOIN Countries " & _ "ON Cities.country=Countries.country " & _ "ORDER BY city ASC") End Sub Ch. 10

  8. Example Lab sheet 10.5: Code continued SubUpdateGrid(ByValsqlStr As String) Dimdt As NewDataTable() DimconnStr As String="Provider=Microsoft.Jet.OLEDB.4.0;" & _ "Data Source = MEGACITIES.MDB" DimdataAdapter As NewOleDb.OleDbDataAdapter(sqlStr, connStr) dataAdapter.Fill(dt) dataAdapter.Dispose() dgvDisplay.DataSource = dt End Sub Ch. 10

  9. Lab sheet 10.5: Output Click on the “Show Monetary Unit” button. Ch. 10

  10. Lab sheet 10.6: Form txtCountry dgvDisplay Ch. 10

  11. Lab sheet 10.6: Code Private SubbtnFindCities_Click(...) _ HandlesbtnFindCities.Click UpdateGrid("SELECT city FROM Cities WHERE" & _ "country = '" & txtCountry.Text & _ "' ORDER BY city ASC") End Sub SubUpdateGrid(ByValsqlStr As String) (Boilerplate, except for Dim sqlStr statement) Ifdt.Rows.Count = 0 Then MsgBox("No cities from that country " & _ "in the database") Else dgvDisplay.DataSource = dt End If End Sub Ch. 10

  12. Lab sheet 10.6: Output Ch. 10

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