Selecting on fields in an outer join

[mdtimo]

I am dealing with three tables with the fields listed below

Time
-index
-tworkdt
-tudef
Cost
-index(links to costudf.index)
-cdisbdt
Costudf (there will be no record fo Costudf for Costs with no udf)
-index
-cudef

I want a querry that will list all the distinct values for both tudef and cudef. I am writing this for an Informix database

I have tried the following

select distinct(tudef) from time
UNION
select distinct(cudef) from cost,outer(costudf)
where cost.cindex=costudf.cindex

My results will display all the values but will display the null value twice. And I can't see how to avoid this.

 

[barbarul2001]

It's strange what you say. The syntax looks ok and i don't know why this does not work.
Do you really need those nulls? If not, it's simple: try to filtrate in where with cudefis not null . senior rdbms specialist