SQL join filling null columns

Question

I have two tables where I need to do a FULL JOIN. Table2 has many missing values that can be found in table1.

I need to combine (if column1, 2 and 3 are the same) and append the information from table2 filling the null values from table1.

TABLE1

Column1	Column2	Column3	measure1	measure2
A	B	DAY1	50	null
A	B	DAY2	10	null

TABLE 2

Column1	Column2	Column3	measure1	measure2
A	B	DAY1	null	100
A	null	DAY3	null	300

DESIRED RESULT

Column1	Column2	Column3	measure1	measure2
A	B	DAY1	50	100
A	B	DAY2	10	null
A	B	DAY3	null	300

In this case, I combined first rows from table1 and table2. For second row in table2 we lookup the value of column2 from table1.1.

Answer 1

You can use FULL OUTER JOIN here:

select 
    coalesce(t1.id, t2.id) id,
    coalesce(t1.c1, t2.c1) c1,
    coalesce(t1.c2, t2.c2) c2
from t1
full outer join t2 on t1.id = t2.id;

SQLize fiddle