diff --git a/sql-logical-optimization.md b/sql-logical-optimization.md
index 66b0d6a8e8613..bcb86ca646a4a 100644
--- a/sql-logical-optimization.md
+++ b/sql-logical-optimization.md
@@ -4,7 +4,7 @@ title: SQL Logical Optimization
 
 # SQL Logical Optimization
 
-This chapter explains some key logic rewrites to help you understand how TiDB generates the final query plan. For example, when you execute the `select * from t where t.a in (select * from t1 where t1.b=t.b)` query in TiDB, you will find that the `IN` sub-query `t.a in (select t1.a from t1 where t1.b=t.b` does not exist because TiDB has made some rewrites here.
+This chapter explains some key logic rewrites to help you understand how TiDB generates the final query plan. For example, when you execute the `select * from t where t.a in (select t1.a from t1 where t1.b=t.b)` query in TiDB, you will find that the `IN` sub-query `t.a in (select t1.a from t1 where t1.b=t.b)` does not exist because TiDB has made some rewrites here.
 
 This chapter introduces the following key rewrites:
 
diff --git a/system-variables.md b/system-variables.md
index 29e0fa7507286..3fe20d91d5228 100644
--- a/system-variables.md
+++ b/system-variables.md
@@ -688,7 +688,7 @@ set tidb_query_log_max_len = 20
 
 ### tidb_skip_isolation_level_check
 
-- Scope: SESSION
+- Scope: SESSION | GLOBAL
 - Default value: 0
 - After this switch is enabled, if an isolation level unsupported by TiDB is assigned to `tx_isolation`, no error is reported. This helps improve compatibility with applications that set (but do not depend on) a different isolation level.