I have tableA 

```
ID | Zipcode |  State  
1  | 76020   |  NULL  
2  | 40508   |  NULL 
3  | 90040   |  NULL 

```

and tableB which covers all zip codes and states for the US 

```
Zipcode |  State

00210   |  NH
00211   |  NH
00212   |  NH

```

How can I update NULL values in tableA from tableB by matching zip codes?