主题：SQLcommand里可以引用变量吗？

Dim aa AS String = "01"

Dim sqlcmd As New SQLCommand
Dim dt As DataTable
sqlcmd.C
sqlcmd.commandtext = "Select *　from {收入} Where 科目代码 = '01'"

dt=sqlcmd.ExecuteReader

怎样将上文中的 '01' 变为变量aa呢？