parser: fix the compatibility problem of `UNION` statement (#6335)#6784

Merged

jackysp merged 1 commit intopingcap:release-2.0from lysu:dev-cp-union1

Jun 8, 2018

+117-62

Commits on Jun 8, 2018

parser: fix the compatibility problem of UNION statement (#6335 )

spongedu
authored and
lysu
committed