add description about limitation (#19068) (#19130)

pingcap · Oct 15, 2024 · c521b72 · c521b72
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diff --git a/sql-statements/sql-statement-change-column.md b/sql-statements/sql-statement-change-column.md
@@ -151,7 +151,7 @@ ERROR 8200 (HY000): Unsupported modify column: change from original type decimal
 * Changes of [Reorg-Data](/sql-statements/sql-statement-modify-column.md#reorg-data-change) types on primary key columns are not supported.
 * Changes of column types on partitioned tables are not supported.
 * Changes of column types on generated columns are not supported.
-* Changes of some data types (for example, some TIME, Bit, Set, Enum, and JSON types) are not supported due to the compatibility issues of the `CAST` function's behavior between TiDB and MySQL.
+* Changes from some data types (for example, TIME, BIT, SET, ENUM, and JSON types) to some other types are not supported due to the compatibility issues of the `CAST` function's behavior between TiDB and MySQL.
 
 ## See also
 

diff --git a/sql-statements/sql-statement-modify-column.md b/sql-statements/sql-statement-modify-column.md
@@ -204,7 +204,7 @@ CREATE TABLE `t1` (
     ERROR 8200 (HY000): Unsupported modify column: table is partition table
     ```
 
-* Does not support modifying some data types (for example, some TIME types, Bit, Set, Enum, JSON) are not supported due to some compatibility issues of the `cast` function's behavior between TiDB and MySQL.
+* Does not support modifying from some data types (for example, some TIME types, BIT, SET, ENUM, JSON) to some other types due to some compatibility issues of the `cast` function's behavior between TiDB and MySQL.
 
     ```sql
     CREATE TABLE t (a DECIMAL(13, 7));

diff --git a/tidb-limitations.md b/tidb-limitations.md
@@ -7,6 +7,10 @@ summary: Learn the usage limitations of TiDB.
 
 This document describes the common usage limitations of TiDB, including the maximum identifier length and the maximum number of supported databases, tables, indexes, partitioned tables, and sequences.
 
+> **Note:**
+>
+> TiDB offers high compatibility with the MySQL protocol and syntax, including many MySQL limitations. For example, a single index can include a maximum of 16 columns. For more information, see [MySQL Compatibility](/mysql-compatibility.md) and the official MySQL documentation.
+
 ## Limitations on identifier length
 
 | Identifier type | Maximum length (number of characters allowed) |