Constants enable you to supply custom text or numbers to the mapping. A constant's value, as the name implies, will remain the same for the duration of the mapping lifetime.
To add a constant to the mapping:
1.Do one of the following:
a.On the Insert menu, click Constant.
b.Right-click the mapping, and select Insert Constant from the context menu.
2.Enter the value of the constant, select the data type ("String", "Number", "All other"), and click OK.
Alternatively, you can also quickly add a constant as follows:
1.Double-click anywhere on an empty mapping area.
2.Do one of the following:
a.To add a string constant, start typing a double quote followed by the constant value. The closing double quote is optional.
b.To add a numeric constant, just type the number.