There are two tables with the type of column is char. when Using a 'like' predicate in a join condition will result in an incorrect result.
Because there is no 'like' operator that left operand and right operand are all bpchar.(bpchar ~~ bpchar), final the operator 'bpchar ~~ text' will be found form candidate set. so database do the cast from bpchar to text, The space at the end of the string was removed during the cast.
A similar complaint was made the other day; Tom's response succinctly sums up the prevailing opinion as to the character type.