Perform the following steps to add a CASE expression
to the SQL query in the
Designer window:
-
Access
the
CASE Expression window. To perform this
task, click
CASE in the drop-down menu for
an Operand in a WHERE, HAVING, or JOIN condition. You can also access
the
CASE option in the Expression column
for any column that is listed in the
Target table field on the
Select tab.
-
Click
New to begin the first condition of the expression.
An editable row appears in the table.
-
Enter
the appropriate WHEN condition and THEN result for the first WHEN
and THEN clause.
-
Add the
remaining WHEN and THEN clauses. You need to add one row for each
clause.
-
Enter
an appropriate value in the
ELSE Result field.
This value is returned for any row that does not satisfy one of the
WHEN and THEN clauses.
-
Click
OK to save the CASE expression and close the window.
The following display depicts a sample completed CASE Expression window.
Sample Completed CASE Expression Window
Note that
the
Operand field is blank. You can specify
the operand only when the conditions in the CASE expression are all
equality tests. The expression in this sample query uses comparison
operators. Therefore, the US.Population column name must be entered
for each WHEN condition in the expression. In the sample query, the
CASE expression is added to a Pop_Group column that has been added
to the target table. The following display depicts the
Select tab.
Sample CASE Expression Query
Note that
the Population column in the
Source table field on the
Select tab is mapped to both
the Population and the Pop_Group columns in the
Target
table field. The second mapping, which links Population
to Pop_Group, is created by the CASE expression described in this
topic.
Note: Make sure that
the option in the
Select* field of the Select
Properties pane is set to
No. The CASE expression is not included in the SQL SELECT statement
when this option is enabled.
