//生成allter语句.
mysql -e "show tables in lt_bbsx;" | tail --lines=+2 | xargs -i echo "ALTER TABLE {} ENGINE=INNODB;" > /tmp/alter_table.sql
mysql > use lt_bbsx;
mysql > alter table pre_forum_postposition drop primary key,add primary key(position,tid);
mysql > ALTER TABLE pre_forum_postposition ENGINE=INNODB;
mysql > source /tmp/alter_table.sql