sql-statement-create-binding: add note about truncation (#21825)

Author: dveeden

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

@@ -311,6 +311,10 @@ Empty set (0.002 sec)
 1 row in set (0.002 sec)
 ```
 
+## SQL statement truncation
+
+When you use `CREATE BINDING ... FROM HISTORY USING PLAN DIGEST`, the binding can fail if the SQL statement stored in [statement summary tables](/statement-summary-tables.md) for that digest is truncated because it is longer than [`tidb_stmt_summary_max_sql_length`](/system-variables.md#tidb_stmt_summary_max_sql_length-new-in-v40). In this case, you need to increase `tidb_stmt_summary_max_sql_length`.
+
 ## MySQL compatibility
 
 This statement is a TiDB extension to MySQL syntax.