oracle sql query to get data from two tables of similar type
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I have two tables ACTUAL AND ESTIMATE.

In ACTUAL table I have
actual_id, sal_id, gal_id, actual_value, process_flag  
1 111 222 10 N  
2 110 223 20 N  

In ESTIMATE table I have
estimate_id, sal_id, gal_id, estimate_value process_flag  
1 111 222 5 N  
2 123 250 15 N  
 
Now I want a final table, which should have record from ACTUAL table and if no record exist for sal_id+gal_id mapping in ACTUAL but exist in ESTIMATE, then populate estimate record.

In FINAL table  
**111 222 10** (since record exist in actual table for 111 222)   
**110 223 20** (since record exist in actual table for 110 223)  
**123 250 15** (since record not exist in actual table but estimate exist for 123 250)    

What should my query look like? 

Thanks
