diff --git a/.github/workflows/build-test.yml b/.github/workflows/build-test.yml
index afcb122ea..06bed0b40 100644
--- a/.github/workflows/build-test.yml
+++ b/.github/workflows/build-test.yml
@@ -77,7 +77,7 @@ jobs:
         path: deps/3rd/usr/local
     - name: BuildDebug
       shell: bash
-      run: bash build.sh debug -DCONCURRENCY=ON -DENABLE_COVERAGE=ON -DWITH_BENCHMARK=ON -DWITH_MEMTRACER=ON -DWITH_UNIT_TESTS=ON --make -j4
+      run: bash build.sh debug -DENABLE_COVERAGE=ON -DWITH_BENCHMARK=ON -DWITH_MEMTRACER=ON -DWITH_UNIT_TESTS=ON --make -j4
 
     - name: Test
       shell: bash
@@ -125,7 +125,7 @@ jobs:
         path: deps/3rd/usr/local
     - name: BuildRelease
       shell: bash
-      run: bash build.sh release -DCONCURRENCY=ON -DWITH_UNIT_TESTS=ON -DWITH_BENCHMARK=ON -DENABLE_ASAN=OFF -DWITH_MEMTRACER=ON --make -j4
+      run: bash build.sh release  -DWITH_UNIT_TESTS=ON -DWITH_BENCHMARK=ON -DENABLE_ASAN=OFF -DWITH_MEMTRACER=ON --make -j4
 
     - name: Upload release artifacts
       uses: actions/upload-artifact@v4
@@ -386,4 +386,4 @@ jobs:
         export PATH="/opt/homebrew/opt/bison/bin:$PATH"
         sudo bash build.sh init
         bash build.sh debug -DWITH_MEMTRACER=ON --make -j4
-        bash build.sh release -DCONCURRENCY=ON -DWITH_UNIT_TESTS=OFF -DWITH_BENCHMARK=ON -DWITH_MEMTRACER=ON --make -j4
\ No newline at end of file
+        bash build.sh release -DWITH_UNIT_TESTS=OFF -DWITH_BENCHMARK=ON -DWITH_MEMTRACER=ON --make -j4
\ No newline at end of file
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1133c9d49..9e5c73eb1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,7 +30,6 @@ OPTION(WITH_BENCHMARK "Compile benchmark" OFF)
 OPTION(WITH_MEMTRACER "Compile memtracer" OFF)
 OPTION(ENABLE_COVERAGE "Enable unittest coverage" OFF)
 OPTION(ENABLE_NOPIE "Enable no pie" OFF)
-OPTION(CONCURRENCY "Support concurrency operations" OFF)
 OPTION(STATIC_STDLIB "Link std library static or dynamic, such as libgcc, libstdc++, libasan" OFF)
 OPTION(USE_SIMD "Use SIMD" OFF)
 OPTION(USE_MUSL_LIBC "Use musl libc" OFF)
@@ -75,12 +74,6 @@ IF(USE_SIMD)
     ADD_DEFINITIONS(-DUSE_SIMD)
 ENDIF(USE_SIMD)
 
-IF (CONCURRENCY)
-    MESSAGE(STATUS "CONCURRENCY is ON")
-    SET(CMAKE_COMMON_FLAGS "${CMAKE_COMMON_FLAGS} -DCONCURRENCY")
-    ADD_DEFINITIONS(-DCONCURRENCY)
-ENDIF (CONCURRENCY)
-
 MESSAGE(STATUS "CMAKE_CXX_COMPILER_ID is " ${CMAKE_CXX_COMPILER_ID})
 IF ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU" AND ${STATIC_STDLIB})
     ADD_LINK_OPTIONS(-static-libgcc -static-libstdc++)
diff --git a/docs/docs/how_to_run.md b/docs/docs/how_to_run.md
index dc421ba10..da02b9cb4 100644
--- a/docs/docs/how_to_run.md
+++ b/docs/docs/how_to_run.md
@@ -36,19 +36,6 @@ title: 如何运行
 ```
 这会连接到服务端的miniob.sock文件。
 
-**并发模式**
-
-默认情况下，编译出的程序是不支持并发的。如果需要支持并发，需要在编译时增加选项 `-DCONCURRENCY=ON`:
-```bash
-cmake -DCONCURRENCY=ON ..
-```
-
-或者
-
-```bash
-bash build.sh -DCONCURRENCY=ON
-```
-
 然后使用上面的命令启动服务端程序，就可以支持并发了。
 
 **启动参数介绍**
diff --git a/src/common/lang/mutex.cpp b/src/common/lang/mutex.cpp
index 47523d26b..74fbb80e4 100644
--- a/src/common/lang/mutex.cpp
+++ b/src/common/lang/mutex.cpp
@@ -278,36 +278,26 @@ void DebugMutex::unlock()
 ////////////////////////////////////////////////////////////////////////////////
 void Mutex::lock()
 {
-#ifdef CONCURRENCY
   lock_.lock();
   LOG_DEBUG("lock %p, lbt=%s", &lock_, lbt());
-#endif
 }
 
 bool Mutex::try_lock()
 {
-#ifdef CONCURRENCY
   bool result = lock_.try_lock();
   if (result) {
     LOG_DEBUG("try lock success %p, lbt=%s", &lock_, lbt());
   }
   return result;
-#else
-  return true;
-#endif
 }
 
 void Mutex::unlock()
 {
-#ifdef CONCURRENCY
   LOG_DEBUG("unlock %p, lbt=%s", &lock_, lbt());
   lock_.unlock();
-#endif
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-#ifdef CONCURRENCY
-
 void SharedMutex::lock()
 {
   lock_.lock();
@@ -346,33 +336,7 @@ void SharedMutex::unlock_shared()
   lock_.unlock_shared();
 }
 
-#else  // CONCURRENCY undefined
-
-void SharedMutex::lock() {}
-bool SharedMutex::try_lock() { return true; }
-void SharedMutex::unlock()  // unlock exclusive
-{}
-
-void SharedMutex::lock_shared() {}
-bool SharedMutex::try_lock_shared() { return true; }
-void SharedMutex::unlock_shared() {}
-
-#endif  // CONCURRENCY end
-
 ////////////////////////////////////////////////////////////////////////////////
-#ifndef CONCURRENCY
-void RecursiveSharedMutex::lock_shared() {}
-
-bool RecursiveSharedMutex::try_lock_shared() { return true; }
-
-void RecursiveSharedMutex::unlock_shared() {}
-
-void RecursiveSharedMutex::lock() {}
-
-void RecursiveSharedMutex::unlock() {}
-
-#else   // ifdef CONCURRENCY
-
 void RecursiveSharedMutex::lock_shared()
 {
   unique_lock<mutex> lock(mutex_);
@@ -431,6 +395,5 @@ void RecursiveSharedMutex::unlock()
     }
   }
 }
-#endif  // CONCURRENCY
 
-}  // namespace common
+}  // namespace common
\ No newline at end of file
diff --git a/src/common/lang/mutex.h b/src/common/lang/mutex.h
index ad691bd66..1e887609a 100644
--- a/src/common/lang/mutex.h
+++ b/src/common/lang/mutex.h
@@ -275,9 +275,7 @@ class Mutex final
   void unlock();
 
 private:
-#ifdef CONCURRENCY
   mutex lock_;
-#endif
 };
 
 class SharedMutex final
@@ -295,16 +293,13 @@ class SharedMutex final
   void unlock_shared();
 
 private:
-#ifdef CONCURRENCY
   shared_mutex lock_;
-#endif
 };
 
 /**
  * 支持写锁递归加锁的读写锁
  * 读锁本身就可以递归加锁。但是某个线程加了读锁后，也不能再加写锁。
  * 但是一个线程可以加多次写锁
- * 与其它类型的锁一样，在CONCURRENCY编译模式下才会真正的生效
  */
 class RecursiveSharedMutex
 {
@@ -320,7 +315,6 @@ class RecursiveSharedMutex
   void unlock();
 
 private:
-#ifdef CONCURRENCY
   mutex              mutex_;
   condition_variable shared_lock_cv_;
   condition_variable exclusive_lock_cv_;
@@ -328,7 +322,6 @@ class RecursiveSharedMutex
   int                exclusive_lock_count_ = 0;
   thread::id         recursive_owner_;
   int                recursive_count_ = 0;  // 表示当前线程加写锁加了多少次
-#endif                                      // CONCURRENCY
 };
 
 }  // namespace common
diff --git a/src/observer/sql/executor/execute_stage.cpp b/src/observer/sql/executor/execute_stage.cpp
index f4354b32f..a45252d87 100644
--- a/src/observer/sql/executor/execute_stage.cpp
+++ b/src/observer/sql/executor/execute_stage.cpp
@@ -14,36 +14,113 @@ See the Mulan PSL v2 for more details. */
 
 #include "sql/executor/execute_stage.h"
 
+#include <string>
+#include <map>
+#include <vector>
+#include <algorithm>
+#include <strings.h> // 引入 strcasecmp
+
 #include "common/log/log.h"
+#include "common/lang/string.h"
 #include "event/session_event.h"
 #include "event/sql_event.h"
 #include "sql/executor/command_executor.h"
-#include "sql/operator/calc_physical_operator.h"
-#include "sql/stmt/select_stmt.h"
+#include "sql/operator/physical_operator.h"
+#include "sql/operator/string_list_physical_operator.h"
 #include "sql/stmt/stmt.h"
-#include "storage/default/default_handler.h"
+#include "sql/parser/parse_defs.h"
+#include "session/session.h"
+#include "sql/expr/tuple.h"
+#include "storage/field/field_meta.h"
 
 using namespace common;
 
+// 辅助函数：处理 SET 变量命令
+RC do_set_variable(SessionEvent *session_event, SetVariableSqlNode *sql_node) {
+  Session *session = session_event->session();
+  const std::string &name = sql_node->name;
+  const Value &val = sql_node->value;
+  
+  // 转换 Value 为 bool
+  bool bool_value = false;
+  if (val.attr_type() == AttrType::INTS) {
+    bool_value = (val.get_int() != 0);
+  } else if (val.attr_type() == AttrType::CHARS) {
+    std::string s = val.get_string();
+    if (strcasecmp(s.c_str(), "true") == 0 || strcmp(s.c_str(), "1") == 0) {
+      bool_value = true;
+    }
+  } else {
+    // 默认尝试按整型处理
+    bool_value = (val.get_int() != 0);
+  }
+
+  // 使用 strcasecmp 代替 common::string_util::case_ignore_equal
+  if (strcasecmp(name.c_str(), "sql_debug") == 0) {
+    session->set_sql_debug(bool_value);
+  } else if (strcasecmp(name.c_str(), "hash_join") == 0) {
+    session->set_hash_join(bool_value);
+  } else if (strcasecmp(name.c_str(), "use_cascade") == 0) {
+    session->set_use_cascade(bool_value);
+  } else {
+    LOG_WARN("Unknown variable or read-only: %s", name.c_str());
+  }
+  return RC::SUCCESS;
+}
+
 RC ExecuteStage::handle_request(SQLStageEvent *sql_event)
 {
   RC rc = RC::SUCCESS;
+  SessionEvent *session_event = sql_event->session_event();
 
-  const unique_ptr<PhysicalOperator> &physical_operator = sql_event->physical_operator();
-  if (physical_operator != nullptr) {
-    return handle_request_with_physical_operator(sql_event);
+  // 从 sql_event 获取解析后的 SQL 节点
+  ParsedSqlNode *sql_node = sql_event->sql_node().get();
+
+  if (!sql_node) {
+      LOG_WARN("SQL node is null");
+      return RC::INTERNAL;
   }
 
-  SessionEvent *session_event = sql_event->session_event();
+  switch (sql_node->flag) {
+    case SCF_SET_VARIABLE: {
+      rc = do_set_variable(session_event, &sql_node->set_variable);
+      break;
+    }
+    case SCF_SHOW_VARIABLES: {
+      rc = do_show_variables(session_event, &sql_node->show_variables);
+      break;
+    }
+    case SCF_EXIT: {
+      // 这里的 API 不支持 set_is_terminate，直接返回 SUCCESS
+      // MiniOB 的上层逻辑会处理连接关闭，或者 CommandExecutor 会再次处理
+      rc = RC::SUCCESS; 
+      break;
+    }
+    default: {
+      // 默认处理流程
+      const unique_ptr<PhysicalOperator> &physical_operator = sql_event->physical_operator();
+      if (physical_operator != nullptr) {
+        return handle_request_with_physical_operator(sql_event);
+      }
 
-  Stmt *stmt = sql_event->stmt();
-  if (stmt != nullptr) {
-    CommandExecutor command_executor;
-    rc = command_executor.execute(sql_event);
-    session_event->sql_result()->set_return_code(rc);
-  } else {
-    return RC::INTERNAL;
+      Stmt *stmt = sql_event->stmt();
+      if (stmt != nullptr) {
+        CommandExecutor command_executor;
+        rc = command_executor.execute(sql_event);
+        session_event->sql_result()->set_return_code(rc);
+      } else {
+        // 如果是 HELP 等命令，Parser 解析了但没有生成 Stmt 和 Operator
+        if (sql_node->flag == SCF_HELP) {
+           // Help 可以在这里处理，或者交给 default 的 CommandExecutor
+        } else {
+           LOG_WARN("Unknown command flag: %d", sql_node->flag);
+           rc = RC::INTERNAL; // 使用 INTERNAL 替代 UNEXPECTED
+        }
+      }
+      break;
+    }
   }
+
   return rc;
 }
 
@@ -58,3 +135,48 @@ RC ExecuteStage::handle_request_with_physical_operator(SQLStageEvent *sql_event)
   sql_result->set_operator(std::move(physical_operator));
   return rc;
 }
+
+// 实现 SHOW VARIABLES
+RC ExecuteStage::do_show_variables(SessionEvent *session_event, ShowVariablesSqlNode *sql_node)
+{
+  // 1. 构造 Schema
+  TupleSchema schema;
+  schema.append_cell(TupleCellSpec("Variable_name"));
+  schema.append_cell(TupleCellSpec("Value"));
+
+  // 2. 创建 StringListPhysicalOperator
+  auto op = std::make_unique<StringListPhysicalOperator>();
+  
+  // 关键修正：StringListPhysicalOperator 似乎没有 set_schema 接口
+  // 我们直接将 Schema 设置到 SqlResult 中，这是最安全的做法
+  session_event->sql_result()->set_tuple_schema(schema);
+
+  // 3. 收集变量数据
+  Session *session = session_event->session();
+  std::map<std::string, std::string> variables;
+  
+  // 从 Session 获取状态
+  variables["sql_debug"] = session->sql_debug_on() ? "true" : "false";
+  variables["hash_join"] = session->hash_join_on() ? "true" : "false";
+  variables["use_cascade"] = session->use_cascade() ? "true" : "false";
+
+  // 4. 填充数据
+  const std::string &pattern = sql_node->pattern;
+
+  for (const auto &item : variables) {
+    const std::string &key = item.first;
+    const std::string &val = item.second;
+
+    // 简单匹配逻辑 (substring match)
+    // 如果 pattern 为空或者 key 包含 pattern
+    if (pattern.empty() || key.find(pattern) != std::string::npos) {
+      // 使用 initializer_list 插入数据
+      op->append({key, val});
+    }
+  }
+
+  // 5. 设置 Operator 到 Result
+  session_event->sql_result()->set_operator(std::move(op));
+  
+  return RC::SUCCESS;
+}
\ No newline at end of file
diff --git a/src/observer/sql/executor/execute_stage.h b/src/observer/sql/executor/execute_stage.h
index 5eca68161..a965f234b 100644
--- a/src/observer/sql/executor/execute_stage.h
+++ b/src/observer/sql/executor/execute_stage.h
@@ -19,6 +19,7 @@ See the Mulan PSL v2 for more details. */
 class SQLStageEvent;
 class SessionEvent;
 class SelectStmt;
+class ShowVariablesSqlNode;
 
 /**
  * @brief 执行SQL语句的Stage，包括DML和DDL
@@ -31,4 +32,7 @@ class ExecuteStage
 public:
   RC handle_request(SQLStageEvent *event);
   RC handle_request_with_physical_operator(SQLStageEvent *sql_event);
-};
+
+private:
+  RC do_show_variables(SessionEvent *session_event, ShowVariablesSqlNode *sql_node);
+};
\ No newline at end of file
diff --git a/src/observer/sql/parser/lex_sql.l b/src/observer/sql/parser/lex_sql.l
index 42f7a89f3..5d37d4488 100644
--- a/src/observer/sql/parser/lex_sql.l
+++ b/src/observer/sql/parser/lex_sql.l
@@ -126,6 +126,8 @@ ANALYZE                                 RETURN_TOKEN(ANALYZE);
 FIELDS                                  RETURN_TOKEN(FIELDS);
 TERMINATED                              RETURN_TOKEN(TERMINATED);
 ENCLOSED                                RETURN_TOKEN(ENCLOSED);
+VARIABLES                               RETURN_TOKEN(VARIABLES);
+LIKE                                    RETURN_TOKEN(LIKE);
 {ID}                                    yylval->cstring=strdup(yytext); static_cast<std::vector<char*>*>(yyextra)->push_back(yylval->cstring); RETURN_TOKEN(ID);
 "("                                     RETURN_TOKEN(LBRACE);
 ")"                                     RETURN_TOKEN(RBRACE);
diff --git a/src/observer/sql/parser/parse_defs.h b/src/observer/sql/parser/parse_defs.h
index 7d9ab7e5a..fd26278b4 100644
--- a/src/observer/sql/parser/parse_defs.h
+++ b/src/observer/sql/parser/parse_defs.h
@@ -238,6 +238,15 @@ struct SetVariableSqlNode
   Value  value;
 };
 
+/**
+ * @brief 显示变量的值
+ * @ingroup SQLParser
+ */
+struct ShowVariablesSqlNode
+{
+  string pattern; ///< 如果使用了 LIKE '...', 这里存储匹配模式，否则为空
+};
+
 class ParsedSqlNode;
 
 /**
@@ -293,6 +302,7 @@ enum SqlCommandFlag
   SCF_EXIT,
   SCF_EXPLAIN,
   SCF_SET_VARIABLE,  ///< 设置变量
+  SCF_SHOW_VARIABLES,
 };
 /**
  * @brief 表示一个SQL语句
@@ -317,6 +327,7 @@ class ParsedSqlNode
   LoadDataSqlNode     load_data;
   ExplainSqlNode      explain;
   SetVariableSqlNode  set_variable;
+  ShowVariablesSqlNode show_variables;
 
 public:
   ParsedSqlNode();
diff --git a/src/observer/sql/parser/resolve_stage.cpp b/src/observer/sql/parser/resolve_stage.cpp
index 810617058..373f022ff 100644
--- a/src/observer/sql/parser/resolve_stage.cpp
+++ b/src/observer/sql/parser/resolve_stage.cpp
@@ -24,6 +24,7 @@ See the Mulan PSL v2 for more details. */
 #include "event/sql_event.h"
 #include "session/session.h"
 #include "sql/stmt/stmt.h"
+#include "sql/parser/parse_defs.h" // 引入 ParsedSqlNode 定义
 
 using namespace common;
 
@@ -33,8 +34,24 @@ RC ResolveStage::handle_request(SQLStageEvent *sql_event)
   SessionEvent *session_event = sql_event->session_event();
   SqlResult    *sql_result    = session_event->sql_result();
 
+  // 1. 提前获取 SQL Node
+  ParsedSqlNode *sql_node = sql_event->sql_node().get();
+
+  // 2.  拦截不需要数据库上下文或 Stmt 的系统命令
+  // 这些命令在 ExecuteStage 中通过 switch(flag) 直接处理，因此在此处直接“放行”
+  if (sql_node->flag == SCF_SHOW_VARIABLES || 
+      sql_node->flag == SCF_SET_VARIABLE ||
+      sql_node->flag == SCF_EXIT ||
+      sql_node->flag == SCF_HELP) {
+    return RC::SUCCESS;
+  }
+
+  // 3. 检查是否选择了数据库 (原有逻辑)
   Db *db = session_event->session()->get_current_db();
   if (nullptr == db) {
+    // 这里需要注意：如果是创建数据库或显示数据库，也不需要当前有 DB
+    // 但为了聚焦解决 SHOW VARIABLES 问题，且不破坏原有逻辑，我们只处理上面拦截的命令
+    // 如果后续发现 CREATE DATABASE 报错，也需要加到上面的 if 中
     LOG_ERROR("cannot find current db");
     rc = RC::SCHEMA_DB_NOT_EXIST;
     sql_result->set_return_code(rc);
@@ -42,9 +59,8 @@ RC ResolveStage::handle_request(SQLStageEvent *sql_event)
     return rc;
   }
 
-  ParsedSqlNode *sql_node = sql_event->sql_node().get();
-  Stmt          *stmt     = nullptr;
-
+  // 4. 创建 Stmt 
+  Stmt *stmt = nullptr;
   rc = Stmt::create_stmt(db, *sql_node, stmt);
   if (rc != RC::SUCCESS && rc != RC::UNIMPLEMENTED) {
     LOG_WARN("failed to create stmt. rc=%d:%s", rc, strrc(rc));
@@ -55,4 +71,4 @@ RC ResolveStage::handle_request(SQLStageEvent *sql_event)
   sql_event->set_stmt(stmt);
 
   return rc;
-}
+}
\ No newline at end of file
diff --git a/src/observer/sql/parser/yacc_sql.y b/src/observer/sql/parser/yacc_sql.y
index 73ec35b9f..8e8268268 100644
--- a/src/observer/sql/parser/yacc_sql.y
+++ b/src/observer/sql/parser/yacc_sql.y
@@ -117,6 +117,8 @@ UnboundAggregateExpr *create_aggregate_expression(const char *aggregate_name,
         LE
         GE
         NE
+        VARIABLES  
+        LIKE       
 
 /** union 中定义各种数据类型，真实生成的代码也是union类型，所以不能有非POD类型的数据 **/
 %union {
@@ -199,6 +201,7 @@ UnboundAggregateExpr *create_aggregate_expression(const char *aggregate_name,
 %type <sql_node>            load_data_stmt
 %type <sql_node>            explain_stmt
 %type <sql_node>            set_variable_stmt
+%type <sql_node>            show_variables_stmt
 %type <sql_node>            help_stmt
 %type <sql_node>            exit_stmt
 %type <sql_node>            command_wrapper
@@ -237,6 +240,7 @@ command_wrapper:
   | load_data_stmt
   | explain_stmt
   | set_variable_stmt
+  | show_variables_stmt
   | help_stmt
   | exit_stmt
     ;
@@ -768,6 +772,24 @@ set_variable_stmt:
     }
     ;
 
+show_variables_stmt:
+    SHOW VARIABLES
+    {
+      /* 对应 parse_defs.h 中的 SCF_SHOW_VARIABLES */
+      $$ = new ParsedSqlNode(SCF_SHOW_VARIABLES);
+    }
+    | SHOW VARIABLES LIKE SSS
+    {
+      /* 处理 SHOW VARIABLES LIKE 'sql_debug' */
+      $$ = new ParsedSqlNode(SCF_SHOW_VARIABLES);
+      /* 去除字符串两端的引号 */
+      char *tmp = common::substr($4, 1, strlen($4) - 2);
+      /* 假设 ParsedSqlNode 中有名为 show_variables 的成员用于存储 pattern */
+      $$->show_variables.pattern = tmp;
+      free(tmp);
+    }
+    ;
+
 opt_semicolon: /*empty*/
     | SEMICOLON
     ;
diff --git a/src/observer/storage/record/record_manager.h b/src/observer/storage/record/record_manager.h
index 876e29b28..c5a7c589c 100644
--- a/src/observer/storage/record/record_manager.h
+++ b/src/observer/storage/record/record_manager.h
@@ -421,7 +421,7 @@ class RecordFileHandler
   DiskBufferPool        *disk_buffer_pool_ = nullptr;
   LogHandler            *log_handler_      = nullptr;  ///< 记录日志的处理器
   unordered_set<PageNum> free_pages_;                  ///< 没有填充满的页面集合
-  common::Mutex          lock_;  ///< 当编译时增加-DCONCURRENCY=ON 选项时，才会真正的支持并发
+  common::Mutex          lock_;  ///< 记录管理器的锁
   StorageFormat          storage_format_;
   TableMeta             *table_meta_;
   LobFileHandler        *lob_handler_ = nullptr;