Update partitioned-table.md

mysql-compatibility.md

@@ -172,7 +172,7 @@ In TiDB, all supported DDL changes can be performed online. However, there are s
 * The `ALGORITHM={INSTANT,INPLACE,COPY}` syntax functions only as an assertion in TiDB, and does not modify the `ALTER` algorithm. See [`ALTER TABLE`](/sql-statements/sql-statement-alter-table.md) for further details.
 * Adding/Dropping the primary key of the `CLUSTERED` type is unsupported. For more details about the primary key of the `CLUSTERED` type, refer to [clustered index](/clustered-indexes.md).
 * Different types of indexes (`HASH|BTREE|RTREE|FULLTEXT`) are not supported, and will be parsed and ignored when specified.
-* TiDB supports `HASH`, `RANGE`, `LIST`, and `KEY` partitioning types. Currently, the `KEY` partition type does not support partition statements with an empty partition column list. For an unsupported partition type, TiDB returns `Warning: Unsupported partition type %s, treat as normal table`, where `%s` is the specific unsupported partition type.
+* TiDB supports `HASH`, `RANGE`, `LIST`, and `KEY` partitioning types. For an unsupported partition type, TiDB returns `Warning: Unsupported partition type %s, treat as normal table`, where `%s` is the specific unsupported partition type.
 * Range, Range COLUMNS, List, and List COLUMNS partitioned tables support `ADD`, `DROP`, `TRUNCATE`, and `REORGANIZE` operations. Other partition operations are ignored.
 * Hash and Key partitioned tables support `ADD`, `COALESCE`, and `TRUNCATE` operations. Other partition operations are ignored.
 * The following syntaxes are not supported for partitioned tables:

partitioned-table.md

@@ -665,11 +665,11 @@ PARTITION BY KEY(fname, store_id)
 PARTITIONS 4;
 ```
 
-Currently, TiDB does not support creating Key partitioned tables if the partition column list specified in `PARTITION BY KEY` is empty. For example, after you execute the following statement, TiDB will create a non-partitioned table and return an `Unsupported partition type KEY, treat as normal table` warning.
+Similar to MySQL, TiDB supports creating Key partitioned tables with an empty partition column list specified in `PARTITION BY KEY`. For example, the following statement creates a partitioned table using the primary key `id` as the partitioning key:
 
 ```sql
 CREATE TABLE employees (
-    id INT NOT NULL,
+    id INT NOT NULL PRIMARY KEY,
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
@@ -682,6 +682,20 @@ PARTITION BY KEY()
 PARTITIONS 4;
 ```
 
+If the table lacks a primary key but contains a unique key, the unique key is used as the partitioning key:
+
+```sql
+CREATE TABLE k1 (
+    id INT NOT NULL,
+    name VARCHAR(20),
+    UNIQUE KEY (id)
+)
+PARTITION BY KEY()
+PARTITIONS 2;
+```
+
+However, the previous statement will fail if the unique key column is not defined as `NOT NULL`.
+
 #### How TiDB handles Linear Hash partitions
 
 Before v6.4.0, if you execute DDL statements of [MySQL Linear Hash](https://dev.mysql.com/doc/refman/8.0/en/partitioning-linear-hash.html) partitions in TiDB, TiDB can only create non-partitioned tables. In this case, if you still want to use partitioned tables in TiDB, you need to modify the DDL statements.
@@ -1682,8 +1696,6 @@ YEARWEEK()
 
 Currently, TiDB supports Range partitioning, Range COLUMNS partitioning, List partitioning, List COLUMNS partitioning, Hash partitioning, and Key partitioning. Other partitioning types that are available in MySQL are not supported yet in TiDB.
 
-Currently, TiDB does not support using an empty partition column list for Key partitioning.
-
 With regard to partition management, any operation that requires moving data in the bottom implementation is not supported currently, including but not limited to: adjust the number of partitions in a Hash partitioned table, modify the Range of a Range partitioned table, and merge partitions.
 
 For the unsupported partitioning types, when you create a table in TiDB, the partitioning information is ignored and the table is created in the regular form with a warning reported.