in index search MySQL was not explicitly
 suppressing warnings. And if the context 
 happens to enable warnings (e.g. INSERT ..
 SELECT) the warnings resulting from converting 
 the data the key is compared to are 
 reported to the client.
 Fixed by suppressing warnings when converting
 the data to the same type as the key parts.


mysql-test/r/insert_select.result:
  Bug #26207: test case
mysql-test/t/insert_select.test:
  Bug #26207: test case
sql/sql_select.h:
  Bug #26207: supress warnings when converting
    data of the same type to key buffer format.