fix: 第二次提交学案分析的时候，sql语句报错

app/Services/ExamAnswerAnalysisService.php

@@ -1300,27 +1300,35 @@ class ExamAnswerAnalysisService
      */
     private function saveExamAnswerRecords(array $examData, array $questionMappings = []): void
     {
-        $studentId = $examData['student_id'];
-        $examId = $examData['paper_id'];
+        // 【修复】确保类型正确，避免 SQL 类型转换问题
+        $studentId = (string) $examData['student_id'];
+        $examId = (string) $examData['paper_id'];
         $now = now();
 
         // 先清理该考试的所有答题记录（支持重复提交）
         try {
             DB::connection('mysql')->table('student_answer_questions')
-                ->where('student_id', $studentId)
-                ->where('exam_id', $examId)
+                ->where('student_id', '=', $studentId)
+                ->where('exam_id', '=', $examId)
                 ->delete();
 
             DB::connection('mysql')->table('student_answer_steps')
-                ->where('student_id', $studentId)
-                ->where('exam_id', $examId)
+                ->where('student_id', '=', $studentId)
+                ->where('exam_id', '=', $examId)
                 ->delete();
+
+            Log::info('清理旧答题记录成功', [
+                'student_id' => $studentId,
+                'exam_id' => $examId,
+            ]);
         } catch (\Exception $e) {
-            Log::warning('清理旧答题记录时出错（可忽略）', [
+            // 清理失败时抛出异常，避免后续插入重复数据
+            Log::error('清理旧答题记录失败', [
                 'student_id' => $studentId,
                 'exam_id' => $examId,
                 'error' => $e->getMessage(),
             ]);
+            throw $e;
         }
 
         // 【优化】收集所有要插入的记录，最后批量INSERT
@@ -1424,7 +1432,7 @@ class ExamAnswerAnalysisService
             }
         }
 
-        // 【优化】批量INSERT（每500条一批，避免超过MySQL限制）
+        // 【优化】批量 INSERT（每500条一批，避免超过MySQL限制）
         try {
             if (!empty($stepsToInsert)) {
                 foreach (array_chunk($stepsToInsert, 500) as $chunk) {