如果创建表时同时设置了主键，OceanBase 数据库会默认创建一个唯一索引。以下面的 SQL 为例：

    创建索引的 SQL 语法格式如下：

    在 MySQL 租户里，新增索引还有一种方法，SQL 语法格式如下：

    • 示例：对分区表新增索引
    1. obclient> create table t3(
    2.     id bigint not null primary KEY
    3.     , name varchar(50)
    4.     , gmt_create timestamp not null default current_timestamp
    5. ) partition by hash(id) partitions 8;
    6. Query OK, 0 rows affected (0.14 sec)
    7. obclient> alter table t3 add unique key t3_uk (name) local;
    10. obclient> alter table t3 
    11.     add unique key t3_uk (name, id) LOCAL
    12.     , add key t3_ind3(gmt_create) global;
    13. Query OK, 0 rows affected (18.03 sec)
    15. obclient> show indexes from t3;
    17. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+
    18. | t3    |          0 | PRIMARY  |            1 | id          | A         |        NULL | NULL     | NULL   |      | BTREE      | available |               | YES     |
    19. | t3    |          0 | t3_uk    |            1 | name        | A         |        NULL | NULL     | NULL   | YES  | BTREE      | available |               | YES     |
    20. | t3    |          0 | t3_uk    |            2 | id          | A         |        NULL | NULL     | NULL   |      | BTREE      | available |               | YES     |
    21. | t3    |          1 | t3_ind3  |            1 | gmt_create  | A         |        NULL | NULL     | NULL   |      | BTREE      | available |               | YES     |
    22. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+-----------+---------------+---------+
    23. 4 rows in set (0.01 sec)

    删除索引

    删除索引的语法格式如下：

    • 示例：删除表的索引