Get none null column row and other row when its null-CodePudding

I have a problem and I wondered if I can do it only with sql.

So I have a table named: tbl, and columns a, b, c which a and b rows aren't null and c can be null, for example:

a	b	c
a1	b1	NULL
a2	b2	c2
a3	b3	NULL

And I wish to get the result with columns a and x when x is defined: take from b when c is null and take from c if its not null, so the output will be:

a	col2
a1	b1
a2	c2
a3	b3

There is a sql command which can do the above?

Thanks

CodePudding user response：

You can use the COALESCE function, given that your DBMS supports it.

SELECT a, 
       COALESCE(c, b)
FROM tab

CodePudding user response：

select a, nvl(c, b) from table;

Thank you

CodePudding user response：

If your DBMS does not support the functions from answers above, you can do it with CASE function:

SELECT
  a,
  CASE
    WHEN c IS NULL THEN b
    ELSE c
    END AS col2
FROM
  tbl