Added a function to delete all data before inserting sample data.

api/source/sample_data.d

@@ -3,6 +3,7 @@ module sample_data;
 import ddbc;
 import db;
 import data_utils;
+import slf4d;
 
 import std.random;
 import std.algorithm;
@@ -40,6 +41,8 @@ void insertSampleData() {
         conn.close();
     }
 
+    deleteAllData(conn);
+
     addUser(conn, "sample-user-A", "test", false, false);
     addUser(conn, "sample-user-B", "test", true, false);
     addUser(conn, "sample-user-C", "test", false, false);
@@ -84,6 +87,7 @@ void insertSampleData() {
             }
         }
     }
+    info("Inserted sample data.");
 }
 
 ulong addUser(Connection conn, string username, string password, bool locked, bool admin) {
@@ -143,3 +147,21 @@ void addEntry(
     }
     ps.executeUpdate();
 }
+
+void deleteAllData(Connection conn) {
+    Statement stmt = conn.createStatement();
+    scope(exit) stmt.close();
+
+    const tables = [
+        "announcement",
+        "classroom_compliance_class_note",
+        "classroom_compliance_entry",
+        "classroom_compliance_student",
+        "classroom_compliance_class",
+        "auth_user"
+    ];
+    foreach (tableName; tables) {
+        int rows = stmt.executeUpdate("DELETE FROM " ~ tableName);
+        infoF!"Deleted %d rows from %s."(rows, tableName);
+    }
+}