用于选择行的单个SQL语句，但仅限于只有一个匹配行

Consider the following SQL:

考虑以下SQL:

SELECT @Count = COUNT(*)
FROM Widgets
WHERE WidgetName = 'foo'

IF ( @Count = 1 ) BEGIN
    SELECT @WidgetId = WidgetId
    FROM Widgets
    WHERE WidgetName = 'foo'
END
SELECT