diff --git a/backend/internal/handler/instance_detail.go b/backend/internal/handler/instance_detail.go
index 850cbe7..9c1d364 100644
--- a/backend/internal/handler/instance_detail.go
+++ b/backend/internal/handler/instance_detail.go
@@ -641,8 +641,10 @@ func executeSQLQuery(instance *model.Instance, dbName string, sqlStr string, lim
 		}
 	}
 
-	// Inject LIMIT/OFFSET if not already present
-	if !hasLimit {
+	// Inject LIMIT/OFFSET if not already present — only for SELECT statements
+	// SHOW/DESC/EXPLAIN/CREATE/ALTER/DROP/etc do not support LIMIT syntax
+	needsLimit := !hasLimit && strings.HasPrefix(upperSQL, "SELECT")
+	if needsLimit {
 		sqlStr = fmt.Sprintf("%s LIMIT %d OFFSET %d", sqlStr, limit, offset)
 	}
 
diff --git a/backend/internal/handler/ticket.go b/backend/internal/handler/ticket.go
index 66a93c3..4a9a94b 100644
--- a/backend/internal/handler/ticket.go
+++ b/backend/internal/handler/ticket.go
@@ -254,6 +254,66 @@ func CreateTicket(c *gin.Context) {
 		}
 	}
 
+	// ── Dangerous SQL blacklist ──
+	// MySQL: block DROP DATABASE / DROP SCHEMA
+	if input.DBType == "mysql" || input.DBType == "postgresql" || input.DBType == "postgres" || input.DBType == "pg" {
+		mysqlBlacklist := []struct {
+			prefix string
+			reason string
+		}{
+			{"DROP DATABASE ", "禁止执行 DROP DATABASE — 删库属于极端危险操作"},
+			{"DROP SCHEMA ", "禁止执行 DROP SCHEMA — 删库属于极端危险操作"},
+		}
+		statements := splitSQL(input.SQLContent)
+		for _, stmt := range statements {
+			upper := strings.ToUpper(strings.TrimSpace(stmt))
+			for _, bl := range mysqlBlacklist {
+				if strings.HasPrefix(upper, bl.prefix) {
+					c.JSON(http.StatusBadRequest, gin.H{"detail": bl.reason})
+					return
+				}
+			}
+			// Warn: UPDATE/DELETE without WHERE
+			if (strings.HasPrefix(upper, "UPDATE ") || strings.HasPrefix(upper, "DELETE FROM ")) &&
+				!strings.Contains(upper, " WHERE ") {
+				c.JSON(http.StatusBadRequest, gin.H{"detail": "禁止无 WHERE 条件的 UPDATE/DELETE — 全表更新/删除属于高危操作，请添加 WHERE 子句限定范围"})
+				return
+			}
+		}
+	}
+
+	// Redis: block extremely dangerous commands
+	if input.DBType == "redis" {
+		redisBlacklist := []struct {
+			cmd    string
+			reason string
+		}{
+			{"FLUSHALL", "禁止执行 FLUSHALL — 清空所有Redis数据"},
+			{"FLUSHDB", "禁止执行 FLUSHDB — 清空当前数据库"},
+			{"CONFIG ", "禁止执行 CONFIG — 修改Redis配置属于高危操作"},
+			{"DEBUG ", "禁止执行 DEBUG — 调试命令可能导致服务异常"},
+			{"SHUTDOWN", "禁止执行 SHUTDOWN — 关闭Redis服务"},
+			{"SCRIPT ", "禁止执行 SCRIPT — 脚本管理属于高危操作"},
+			{"SAVE", "禁止执行 SAVE — 阻塞式持久化"},
+			{"BGSAVE", "禁止执行 BGSAVE — 后台持久化由运维管理"},
+			{"BGREWRITEAOF", "禁止执行 BGREWRITEAOF — AOF重写由运维管理"},
+			{"SLAVEOF", "禁止执行 SLAVEOF — 主从切换属于运维操作"},
+			{"REPLICAOF", "禁止执行 REPLICAOF — 主从切换属于运维操作"},
+			{"CLUSTER ", "禁止执行 CLUSTER — 集群管理属于运维操作"},
+			{"KEYS ", "禁止执行 KEYS — 生产环境应使用 SCAN 替代，KEYS 会阻塞Redis"},
+		}
+		cmdParts := parseCommandParts(input.SQLContent)
+		if len(cmdParts) > 0 {
+			upperCmd := strings.ToUpper(cmdParts[0])
+			for _, bl := range redisBlacklist {
+				if upperCmd == strings.TrimSuffix(bl.cmd, " ") || strings.HasPrefix(upperCmd+" ", bl.cmd) {
+					c.JSON(http.StatusBadRequest, gin.H{"detail": bl.reason})
+					return
+				}
+			}
+		}
+	}
+
 	// Auto-fill workflow_id from instance if not provided
 	if input.WorkflowID == nil || *input.WorkflowID == 0 {
 		var inst model.Instance
@@ -733,30 +793,48 @@ func ExecuteTicket(c *gin.Context) {
 					return
 				}
 			}
-		// Split multi-statement by semicolons
+		// Split multi-statement by semicolons — wrap in transaction for atomic rollback
 			execStart := time.Now()
 			statements := splitSQL(ticket.SQLContent)
 			execRes := SqlExecResult{Status: "success", StartTime: execStart.UTC().Format(time.RFC3339)}
-			for _, stmt := range statements {
-				stmt = strings.TrimSpace(stmt)
-				if stmt == "" {
-					continue
-				}
-				stmtStart := time.Now()
-				sqlResult, err := db.ExecContext(ctx, stmt)
-				stmtMs := time.Since(stmtStart).Milliseconds()
-				if err != nil {
+			// Begin transaction for multi-statement execution
+			tx, txErr := db.BeginTx(ctx, nil)
+			if txErr != nil {
+				execErr = fmt.Sprintf("开启事务失败: %v", txErr)
+			} else {
+				committed := false
+				for _, stmt := range statements {
+					stmt = strings.TrimSpace(stmt)
+					if stmt == "" {
+						continue
+					}
+					stmtStart := time.Now()
+					sqlResult, err := tx.ExecContext(ctx, stmt)
+					stmtMs := time.Since(stmtStart).Milliseconds()
+					if err != nil {
+						execRes.Items = append(execRes.Items, SqlExecItem{
+							SQL: stmt, Status: "fail", DurationMs: stmtMs, Error: err.Error(),
+						})
+						execRes.Status = "failed"
+						execErr = err.Error()
+						// Rollback on any failure
+						tx.Rollback()
+						break
+					}
+					affected, _ := sqlResult.RowsAffected()
 					execRes.Items = append(execRes.Items, SqlExecItem{
-						SQL: stmt, Status: "fail", DurationMs: stmtMs, Error: err.Error(),
+						SQL: stmt, Status: "success", AffectedRows: affected, DurationMs: stmtMs,
 					})
-					execRes.Status = "failed"
-					execErr = err.Error()
-					break
 				}
-				affected, _ := sqlResult.RowsAffected()
-				execRes.Items = append(execRes.Items, SqlExecItem{
-					SQL: stmt, Status: "success", AffectedRows: affected, DurationMs: stmtMs,
-				})
+				if execErr == "" {
+					if commitErr := tx.Commit(); commitErr != nil {
+						execRes.Status = "failed"
+						execErr = fmt.Sprintf("事务提交失败: %v", commitErr)
+					} else {
+						committed = true
+					}
+				}
+				_ = committed
 			}
 			execRes.TotalMs = time.Since(execStart).Milliseconds()
 			execRes.EndTime = time.Now().UTC().Format(time.RFC3339)