VARCHAR and Equality Comparison

This is a follow-up on the previous post.

Now that we know trailing space(s) is 'not that important' as far as DB2 is concerned, what would you expect in a simple '=' comparison?

Let's do a little test:



db2 => create table smallt (c1 varchar(4)) ;
DB20000I  The SQL command completed successfully.

db2 => insert into smallt values 'B', 'B ', 'B  ';
DB20000I  The SQL command completed successfully.

db2 => select length(c1), c1 from smallt ;

1           C1
----------- ----
          1 B
          2 B
          3 B

  3 record(s) selected.


We have three rows with different 'length' due to the trailing space(s) we inserted. If we compare this column to itself, ie, c1 = c1, how many rows would you expect?

Three?

Let's see ...



db2 => select * from smallt t1, smallt t2 where t1.c1 = t2.c1 ;

C1   C1
---- ----
B    B
B    B
B    B
B    B
B    B
B    B
B    B
B    B
B    B

  9 record(s) selected.


Need I say more? ;)