Q

Joining tables without JOIN or subqueries

I have two tables names T1 and T2 like below,

T1
---
slNo  value
----  ------
1      A
2      NULL
3      C

T2
---
slNo  value
----  ------
1      NULL
2      B
3      NULL
Based on these two tables, I need a third table like the following one:
T3
--
slNo  value
----  ------
1      A
2      B
3      C
So, I need a SQL query without using any JOIN operations, nested queries or subqueries to get the third table T3.


Without using joins or subqueries, you're really limiting my choice of tools. But it can be done. Here goes:

select slNo, value from T1 where value is not null
union 
select slNo, value from T2 where value is not null;

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This was first published in March 2002

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