DDL 拆分函数概述

DRDS DDL 拆分函数对分库分表的支持情况


DRDS 是一个支持既分库又分表的数据库服务。目前 DRDS 分库函数与分表函数的支持情况如下：

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  [backcolor=transparent]DRDS 分库分表拆分方式的注意点
  在 DRDS 中，一张逻辑表的[backcolor=transparent]拆分方式是由拆分函数（包括分片数目与路由算法）与拆分键（包括拆分键的 MySQL 数据类型）共同定义。
• 
  只有当 DRDS 的分库函数与分表函数相同并且分库键与分表键也相同时，才会被认为分库与分表都使用了共同的拆分方式。这样的方式可以让 DRDS 可以根据拆分键的值唯一定位到一个物理分库与一张物理分表。
• 
  当一张逻辑表的分库拆分方式与分表拆分方式不一致时，若 SQL 查询没有同时带上分库条件与分表条件，则 DRDS 在查询过程会产生全分库扫描或全分表扫描的操作。

1. [backcolor=transparent]CREATE [backcolor=transparent][[backcolor=transparent]TEMPORARY[backcolor=transparent]][backcolor=transparent] TABLE [backcolor=transparent][[backcolor=transparent]IF NOT EXISTS[backcolor=transparent]][backcolor=transparent] tbl_name
2. [backcolor=transparent]    [backcolor=transparent]([backcolor=transparent]create_definition[backcolor=transparent],...)
3. [backcolor=transparent]    [backcolor=transparent][[backcolor=transparent]table_options[backcolor=transparent]]
4. [backcolor=transparent]    [backcolor=transparent][[backcolor=transparent]drds_partition_options[backcolor=transparent]]
5. [backcolor=transparent]    [backcolor=transparent][[backcolor=transparent]partition_options[backcolor=transparent]]
7. [backcolor=transparent]CREATE [backcolor=transparent][[backcolor=transparent]TEMPORARY[backcolor=transparent]][backcolor=transparent] TABLE [backcolor=transparent][[backcolor=transparent]IF NOT EXISTS[backcolor=transparent]][backcolor=transparent] tbl_name
8. [backcolor=transparent]    [backcolor=transparent][([backcolor=transparent]create_definition[backcolor=transparent],...)]
9. [backcolor=transparent]    [backcolor=transparent][[backcolor=transparent]table_options[backcolor=transparent]]
10. [backcolor=transparent]    [backcolor=transparent][[backcolor=transparent]drds_partition_options[backcolor=transparent]]
11. [backcolor=transparent]    [backcolor=transparent][[backcolor=transparent]partition_options[backcolor=transparent]]
12. [backcolor=transparent]    select_statement
14. [backcolor=transparent]drds_partition_options[backcolor=transparent]:
15. [backcolor=transparent]    DBPARTITION BY
16. [backcolor=transparent]        [backcolor=transparent]{[backcolor=transparent] [backcolor=transparent]{[backcolor=transparent]HASH[backcolor=transparent]|[backcolor=transparent]YYYYMM[backcolor=transparent]|[backcolor=transparent]YYYYWEEK[backcolor=transparent]|[backcolor=transparent]YYYYDD[backcolor=transparent]|[backcolor=transparent]YYYYMM_OPT[backcolor=transparent]|[backcolor=transparent]YYYYWEEK_OPT[backcolor=transparent]|[backcolor=transparent]YYYYDD_OPT[backcolor=transparent]}([[backcolor=transparent]column[backcolor=transparent]])}
17. [backcolor=transparent]        [backcolor=transparent][[backcolor=transparent]TBPARTITION BY
18. [backcolor=transparent]            [backcolor=transparent]{[backcolor=transparent] [backcolor=transparent]{[backcolor=transparent]HASH[backcolor=transparent]|[backcolor=transparent]MM[backcolor=transparent]|[backcolor=transparent]DD[backcolor=transparent]|[backcolor=transparent]WEEK[backcolor=transparent]|[backcolor=transparent]MMDD[backcolor=transparent]|[backcolor=transparent]YYYYMM[backcolor=transparent]|[backcolor=transparent]YYYYWEEK[backcolor=transparent]|[backcolor=transparent]YYYYDD[backcolor=transparent]|[backcolor=transparent]YYYYMM_OPT[backcolor=transparent]|[backcolor=transparent]YYYYWEEK_OPT[backcolor=transparent]|[backcolor=transparent]YYYYDD_OPT[backcolor=transparent]}([backcolor=transparent]column[backcolor=transparent])}
19. [backcolor=transparent]          [backcolor=transparent][[backcolor=transparent]TBPARTITIONS num[backcolor=transparent]]
20. [backcolor=transparent]        [backcolor=transparent]]