InterBase中带文字的联合查询

Question

I have just started using Interbase and I am trying to run the simple query. When I have 'SEQUENCE' (or 'INDEX' or 'something') in BOTH part of union query it works fine, but when I have different strings in two parts of the query it produces an error:

Data type unknown.

select rdb$generator_name as name, 'SEQUENCE' as typ from rdb$generators 
where upper(rdb$generator_name) like '%RD%' 
union all 
select rdb$index_name as name, 'INDEX' as typ from rdb$indices 
where upper(rdb$index_name) like '%RD%';

Therefore, the question is: how could I specify the type or what other thing I could do to run the query?

Thanks in advance

Answer 1

We can solve it using type casting:

select rdb$generator_name as name, cast('SEQUENCE' as varchar(10)) as typ from rdb$generators
where upper(rdb$generator_name) like '%RD%' 
union all 
select rdb$index_name as name, cast('INDEX' as varchar(10)) as typ from rdb$indices
where upper(rdb$index_name) like '%RD%';