Will SQL update a record if there is no change to the record?

For examople, is it more efficient to replace 

```
UPDATE TABLE myTable 
Set Col1 = ISNULL(Col1,'')
...
Set Col100 = ISNULL(Col30,'')

```

with

```
UPDATE TABLE myTable 
Set Col1 = ISNULL(Col1,'')
...
Set Col100 = ISNULL(Col30,'')
WHERE 
Col1 IS NULL OR
...
Col30 IS NULL

```