So i have the following query

Select id, [First], [Last] , [Business] as contactbusiness, (Case When ([Business] != '' or [Business] is not null) 
        Then [Business] Else 'No Phone Number' END) from contacts

The results look like

id  First   Last    contactbusiness (No column name)
2   John    Smith       
3   Sarah   Jane    0411 111 222    0411 111 222
6   John    Smith   0411 111 111    0411 111 111
8                   NULL            No Phone Number
11  Ryan    B       08 9999 9999    08 9999 9999
14  David   F       NULL            No Phone Number

I'd expect record 2 to also show No Phone Number

If i change the "[Business] is not null" to [Business] != null then i get the correct results

id  First   Last    contactbusiness (No column name)
2   John    Smith                   No Phone Number
3   Sarah   Jane    0411 111 222    0411 111 222
6   John    Smith   0411 111 111    0411 111 111
8                   NULL            No Phone Number
11  Ryan    B       08 9999 9999    08 9999 9999
14  David   F       NULL            No Phone Number

Normally you need to use is not null rather than != null. whats going on here?