azexcy commented on PR #27983:
URL: https://github.com/apache/shardingsphere/pull/27983#issuecomment-1668865510
The primary key will have a unique index
MySQL
```
mysql> CREATE TABLE t_order (order_id INT NOT NULL, user_id INT NOT NULL,
status VARCHAR(50), PRIMARY KEY (order_id))
mysql> describe t_order;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| order_id | int | NO | PRI | NULL | |
| user_id | int | NO | | NULL | |
| status | varchar(50) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.01 sec)
mysql> SHOW INDEX FROM t_order;
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation |
Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
Visible | Expression |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| t_order | 0 | PRIMARY | 1 | order_id | A |
0 | NULL | NULL | | BTREE | | |
YES | NULL |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
1 row in set (0.01 sec)
```
PostgreSQL
```
create table t_order (
order_id integer primary key ,
user_id integer not null,
status character varying(255)
);
postgres=# \c ds_0
You are now connected to database "ds_0" as user "aze".
ds_0=# \d t_order
Table "public.t_order"
Column | Type | Collation | Nullable | Default
----------+------------------------+-----------+----------+---------
order_id | integer | | not null |
user_id | integer | | not null |
status | character varying(255) | | |
Indexes:
"t_order_pkey" PRIMARY KEY, btree (order_id)
ds_0=# SELECT * FROM pg_indexes WHERE tablename = 't_order';
schemaname | tablename | indexname | tablespace |
indexdef
------------+-----------+--------------+------------+---------------------------------------------------------------------------
public | t_order | t_order_pkey | | CREATE UNIQUE INDEX
t_order_pkey ON public.t_order USING btree (order_id)
(1 row)
ds_0=#
```
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