fix partition table doc error (#5903) (#5911)

partitioned-table.md

@@ -27,8 +27,8 @@ CREATE TABLE employees (
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
-    separated DATE NOT NULL DEFAULT '9999-12-31',
-    job_code INT NOT NULL,
+    separated DATE DEFAULT '9999-12-31',
+    job_code INT,
     store_id INT NOT NULL
 );
 ```
@@ -43,8 +43,8 @@ CREATE TABLE employees (
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
-    separated DATE NOT NULL DEFAULT '9999-12-31',
-    job_code INT NOT NULL,
+    separated DATE DEFAULT '9999-12-31',
+    job_code INT,
     store_id INT NOT NULL
 )
 
@@ -58,7 +58,7 @@ PARTITION BY RANGE (store_id) (
 
 In this partition scheme, all rows corresponding to employees whose `store_id` is 1 through 5 are stored in the `p0` partition while all employees whose `store_id` is 6 through 10 are stored in `p1`. Range partitioning requires the partitions to be ordered, from lowest to highest.
 
-If you insert a row of data `(72, 'Tom', 'John', '2015-06-25', NULL, 15)`, it falls in the `p2` partition. But if you insert a record whose `store_id` is larger than 20, an error is reported because TiDB can not know which partition this record should be inserted into. In this case, you can use `MAXVALUE` when creating a table:
+If you insert a row of data `(72, 'Tom', 'John', '2015-06-25', NULL, NULL, 15)`, it falls in the `p2` partition. But if you insert a record whose `store_id` is larger than 20, an error is reported because TiDB can not know which partition this record should be inserted into. In this case, you can use `MAXVALUE` when creating a table:
 
 {{< copyable "sql" >}}
 
@@ -68,8 +68,8 @@ CREATE TABLE employees (
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
-    separated DATE NOT NULL DEFAULT '9999-12-31',
-    job_code INT NOT NULL,
+    separated DATE DEFAULT '9999-12-31',
+    job_code INT,
     store_id INT NOT NULL
 )
 
@@ -93,8 +93,8 @@ CREATE TABLE employees (
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
-    separated DATE NOT NULL DEFAULT '9999-12-31',
-    job_code INT NOT NULL,
+    separated DATE DEFAULT '9999-12-31',
+    job_code INT,
     store_id INT NOT NULL
 )
 
@@ -117,7 +117,7 @@ CREATE TABLE employees (
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
-    separated DATE NOT NULL DEFAULT '9999-12-31',
+    separated DATE DEFAULT '9999-12-31',
     job_code INT,
     store_id INT
 )
@@ -293,7 +293,7 @@ CREATE TABLE employees_1 (
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
-    separated DATE NOT NULL DEFAULT '9999-12-31',
+    separated DATE DEFAULT '9999-12-31',
     job_code INT,
     store_id INT,
     city VARCHAR(15)
@@ -318,7 +318,7 @@ CREATE TABLE employees_2 (
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
-    separated DATE NOT NULL DEFAULT '9999-12-31',
+    separated DATE DEFAULT '9999-12-31',
     job_code INT,
     store_id INT,
     city VARCHAR(15)
@@ -367,7 +367,7 @@ CREATE TABLE employees (
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
-    separated DATE NOT NULL DEFAULT '9999-12-31',
+    separated DATE DEFAULT '9999-12-31',
     job_code INT,
     store_id INT
 )
@@ -388,7 +388,7 @@ CREATE TABLE employees (
     fname VARCHAR(30),
     lname VARCHAR(30),
     hired DATE NOT NULL DEFAULT '1970-01-01',
-    separated DATE NOT NULL DEFAULT '9999-12-31',
+    separated DATE DEFAULT '9999-12-31',
     job_code INT,
     store_id INT
 )