diff --git a/functions-and-operators/string-functions.md b/functions-and-operators/string-functions.md
index d6c9f6bf1ad7b..6f7f763e274b7 100644
--- a/functions-and-operators/string-functions.md
+++ b/functions-and-operators/string-functions.md
@@ -6,7 +6,7 @@ aliases: ['/docs/dev/functions-and-operators/string-functions/','/docs/dev/refer
 
 # String Functions
 
-TiDB supports most of the [string functions](https://dev.mysql.com/doc/refman/5.7/en/string-functions.html) available in MySQL 5.7, some of the [string functions](https://dev.mysql.com/doc/refman/8.0/en/string-functions.html) available in MySQL 8.0, and some of the [functions](https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlqr/SQL-Functions.html#GUID-93EC62F8-415D-4A7E-B050-5D5B2C127009) available in Oracle 21.
+TiDB supports most of the [string functions](https://dev.mysql.com/doc/refman/8.0/en/string-functions.html) available in MySQL 8.0, and some of the [functions](https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlqr/SQL-Functions.html#GUID-93EC62F8-415D-4A7E-B050-5D5B2C127009) available in Oracle 21.
 
 <CustomContent platform="tidb">