Align 6 PRs from docs-cn (#7887)

Author: TomShawn

data-type-string.md

@@ -12,7 +12,7 @@ TiDB supports all the MySQL string types, including `CHAR`, `VARCHAR`, `BINARY`,
 
 ### `CHAR` type
 
-`CHAR` is a fixed length string. Values stored as `CHAR` are right-padded with spaces to the specified length. M represents the column-length in characters (not bytes).  The range of M is 0 to 255:
+`CHAR` is a fixed length string. M represents the column-length in characters (not bytes). The range of M is 0 to 255. Different from the `VARCHAR` type, when data is inserted into a `CHAR` column, the trailing spaces are truncated.
 
 ```sql
 [NATIONAL] CHAR[(M)] [CHARACTER SET charset_name] [COLLATE collation_name]

mysql-compatibility.md

@@ -147,7 +147,7 @@ TiDB supports storage engine abstraction similar to MySQL, but you need to speci
 
 TiDB supports most [SQL modes](/sql-mode.md):
 
-- The compatibility modes, such as `ORACLE` and `POSTGRESQL` are parsed but ignored. Compatibility modes are deprecated in MySQL 5.7 and removed in MySQL 8.0.
+- The compatibility modes, such as `Oracle` and `PostgreSQL` are parsed but ignored. Compatibility modes are deprecated in MySQL 5.7 and removed in MySQL 8.0.
 - The `ONLY_FULL_GROUP_BY` mode has minor [semantic differences](/functions-and-operators/aggregate-group-by-functions.md#differences-from-mysql) from MySQL 5.7.
 - The `NO_DIR_IN_CREATE` and `NO_ENGINE_SUBSTITUTION` SQL modes in MySQL are accepted for compatibility, but are not applicable to TiDB.
 

sql-plan-replayer.md

@@ -43,7 +43,7 @@ Based on `sql-statement`, TiDB sorts out and exports the following on-site infor
 ```sql
 use test;
 create table t(a int, b int);
-insert into t valuse(1,1), (2, 2), (3, 3);
+insert into t values(1,1), (2, 2), (3, 3);
 analyze table t;
 
 plan replayer dump explain select * from t;

sql-statements/sql-statement-create-index.md

@@ -127,7 +127,7 @@ You can also specify the expression index when you create the table:
 {{< copyable "sql" >}}
 
 ```sql
-CREATE TABLE t1(col1 char(10), col2 char(10), key index((lower(col1))));
+CREATE TABLE t1(col1 char(10), col2 char(10), index((lower(col1))));
 ```
 
 > **Note**

sql-statements/sql-statement-explain.md

@@ -245,7 +245,6 @@ If the `dot` program is not installed on your computer, copy the result to [this
 
 * Both the format of `EXPLAIN` and the potential execution plans in TiDB differ substaintially from MySQL.
 * TiDB does not support the `FORMAT=JSON`  or `FORMAT=TREE` options.
-* TiDB does not currently support `EXPLAIN` for insert statements.
 
 ### `EXPLAIN FOR CONNECTION`