How to concatenate strings in a request???

[Emmanuel Jotterand]

I could not find any answer, just ignored from documentation...

+ is for numerical value

. do not work

& do not work

what else should be tried???

I want to use a Like with textual values taken from 2 cells, and I need to include the '%' to accept any other caracter which should be present at the strings extremity...

I have a cell which is calculated, and which is the mix of culumn B and C, so I wrote 

=QUERY(A!B2:K;"select B where (I contains 'Observatoire') AND ('"&'Bâtiments'!K26&"' LIKE '%'.B.'%'.D.'%')";-1)

Will try with

=QUERY(A!B2:K;"select B where (I contains 'Observatoire') AND ('"&'Bâtiments'!K26&"' LIKE '%B%D%')";-1)

but how can it be interpreted as B and D are columns and not text??? The last one return #N/A ! What a stupid thing letting things so well done but unfinished, they just ignored users of such developments... Google do not care of human beings...