Why is latin1 used?

[Fabian Uhlenbrock]

Hello,

i've got some Problems with an update to mysql 5.6 from 5.5.
All server variables are set to utf8. All columns are collation of utf8_german2_ci or utf8_unicode_ci.

If i make an select statement like "select COLUMN from TABLE where Column > 0" it works. When i add collate utf8_unicode_ci at the end of the statement it produces this error:
#1253 - COLLATION 'utf8_unicode_ci' is not valid for CHARACTER SET 'latin1'
Selected Column is an Integer used for a foreign key.

i have to use COLLATE in it, because in an UNION of two Select statements the Database shows this Error: #1271 - Illegal mix of collations for operation 'UNION'


But all is utf8 (utf8_unicode_ci & utf8_german2_ci), where does latin1 come from?

Much thanks and best regards

Fabian