I have a table as below

Id, String, Numeric, Date are the column names. Id is the primary key. Id is going to have only one value (either string or numeric or date).

How to I get single value for single Id using select query leaving null values of other respective columns

I tried

select String OR Numeric OR Date 
from Table t 
where id = '2';

CodePudding user response：

You could use the coalesce function to do this

select COALESCE(String, Numeric::text, Date::text) 
from Table t 
where id = '2';

This will give back the first non-null value out of the three columns or null if all three columns are null. The output of this query is a string however, so depending on your application you might have the recast the result back again later. You could also consider using a case instead

SELECT
    CASE WHEN string IS NOT NULL THEN string
         WHEN numeric IS NOT NULL THEN numeric::string
         WHEN date IS NOT NULL THEN date::string 
         ELSE NULL 
    END 
FROM
    Table t 
WHERE
    id = '2';

This will get very messy when there are lots of columns so I wouldn't recommend it in general, but it does allow for some extra flexibility on the output if required.