select
建议带上 shardkey 字段，proxy 根据该字段的 hash 值直接将 SQL 请求路由至对应的数据库实例进行处理；否则就需要发送给集群中所有的数据库实例执行，然后 proxy 根据数据库返回的结果集进行聚合，影响执行效率：
mysql> select * from test1 where a=2;+------+------+---------+| a | b | c |+------+------+---------+| 2 | 3 | record2 || 2 | 4 | record3 |+------+------+---------+2 rows in set (0.00 sec)
insert/replace
字段必须包含 shardkey，否则会拒绝执行该 SQL，因为 proxy 不知道将该 SQL 发往哪个后端数据库：
mysql> insert into test1 (b,c) values(4,"record3");ERROR 810 (HY000): Proxy ERROR:sql is too complex,need to send to only noshard table.Shard table insert must has field specmysql> insert into test1 (a,c) values(4,"record3");Query OK, 1 row affected (0.01 sec)
delete/update
使用分表时，为安全考虑，执行该类 SQL 时，必须带有 where 条件，否则拒绝执行该 SQL 命令：
mysql> delete from test1;ERROR 810 (HY000): Proxy ERROR:sql is too complex,need to send to only noshard table.Shard table delete/update must have a where clausemysql> delete from test1 where a=1;Query OK, 1 row affected (0.01 sec)