I have table A:

```
ColA |  ColB          
  A  |   0    
  B  |   0      
  C  |   0      

```

and table B:

```
ColA |  ColB          
  A  |   10    
  D  |   50      

```

I want to use LEFT OUTER JOIN that if rows of right table exists then it will use right table else use the left table. The result I want is:

```
ColA |  ColB          
  A  |   10    
  B  |   0      
  C  |   0  

```