分库不分表如何实现？

文介绍如何在建表时只分库不分表。

假设已经建好的分库数为 8，建一张表，只分库不分表，分库方式为根据 id 列哈希。

CREATE TABLE multi_db_single_tbl(
  id int,
  name varchar(30),
  primary key(id)
) dbpartition by hash(id);
查看该逻辑表的节点拓扑，可以看出在每个分库都创建了 1 张分表，既只做了分库。

mysql> show topology from multi_db_single_tbl;
+------+------------------------------------------------------------------+---------------------+
| ID   | GROUP_NAME                                                       | TABLE_NAME          |
+------+------------------------------------------------------------------+---------------------+
|    0 | SANGUAN_TEST_123_1488766060743ACTJSANGUAN_TEST_123_WVVP_0000_RDS | multi_db_single_tbl |
|    1 | SANGUAN_TEST_123_1488766060743ACTJSANGUAN_TEST_123_WVVP_0001_RDS | multi_db_single_tbl |
|    2 | SANGUAN_TEST_123_1488766060743ACTJSANGUAN_TEST_123_WVVP_0002_RDS | multi_db_single_tbl |
|    3 | SANGUAN_TEST_123_1488766060743ACTJSANGUAN_TEST_123_WVVP_0003_RDS | multi_db_single_tbl |
|    4 | SANGUAN_TEST_123_1488766060743ACTJSANGUAN_TEST_123_WVVP_0004_RDS | multi_db_single_tbl |
|    5 | SANGUAN_TEST_123_1488766060743ACTJSANGUAN_TEST_123_WVVP_0005_RDS | multi_db_single_tbl |
|    6 | SANGUAN_TEST_123_1488766060743ACTJSANGUAN_TEST_123_WVVP_0006_RDS | multi_db_single_tbl |
|    7 | SANGUAN_TEST_123_1488766060743ACTJSANGUAN_TEST_123_WVVP_0007_RDS | multi_db_single_tbl |
+------+------------------------------------------------------------------+---------------------+
8 rows in set (0.01 sec)