select a.TABLE_SCHEMA,a.TABLE_NAME,a.COLUMN_NAME,a.DATA_TYPE,a.COLUMN_DEFAULT
from information_schema.`COLUMNS` a 
where a.TABLE_SCHEMA='db1' and a.COLUMN_NAME NOT IN(SELECT b.COLUMN_NAME from information_schema.`COLUMNS` b where b.TABLE_SCHEMA='db2' and a.TABLE_SCHEMA='db1'
and a.TABLE_NAME=b.TABLE_NAME );

db1中的表字段在db2中不存在

select a.TABLE_SCHEMA,a.TABLE_NAME,a.COLUMN_NAME,a.DATA_TYPE,a.COLUMN_DEFAULT
from information_schema.`COLUMNS` a 
where a.TABLE_SCHEMA='db2' and a.COLUMN_NAME NOT IN(SELECT b.COLUMN_NAME from information_schema.`COLUMNS` b where b.TABLE_SCHEMA='db1' and a.TABLE_SCHEMA='db2'
and a.TABLE_NAME=b.TABLE_NAME );

db2中的表字段在db1中不存在