fix(sqlite): retain column names when query returns zero rows in SqliteSqlWorkspace

lib/core/database/sqlite_connection.dart

@@ -3,6 +3,7 @@ import 'dart:io';
 
 import 'package:flutter/foundation.dart';
 import 'package:sqflite_common_ffi/sqflite_ffi.dart';
+import 'package:querya_desktop/core/database/sql_table_target_extractor.dart';
 import 'package:querya_desktop/core/database/sqlite_sql.dart';
 import 'package:querya_desktop/core/database/table_schema_meta.dart';
 import 'package:querya_desktop/core/storage/local_db.dart';
@@ -309,6 +310,49 @@ class SqliteConnection {
     return rows.map((r) => r['name'] as String).toList();
   }
 
+  /// Attempts to infer column names for a query (even when it yields zero rows)
+  /// using an ephemeral TEMP VIEW, or falling back to single-table schema.
+  Future<List<String>> inferQueryColumns(String sql) async {
+    if (!isConnected || _db == null) return const [];
+    final trimmed = sqliteStripSqlComments(sql).trim();
+    if (trimmed.isEmpty) return const [];
+
+    // 1. Try temporary view probe in SQLite's in-memory temp schema.
+    const viewName = '_querya_zero_row_col_probe';
+    try {
+      var cleanSql = trimmed;
+      while (cleanSql.endsWith(';')) {
+        cleanSql = cleanSql.substring(0, cleanSql.length - 1).trim();
+      }
+      // Note: We execute on _db! directly to bypass readOnly restriction,
+      // as temp views only touch in-memory session temp schema.
+      await _db!.execute('CREATE TEMP VIEW IF NOT EXISTS $viewName AS $cleanSql');
+      final rows = await _db!.rawQuery('PRAGMA table_info($viewName)');
+      final cols = rows
+          .map((r) => r['name'] as String? ?? '')
+          .where((n) => n.isNotEmpty)
+          .toList();
+      await _db!.execute('DROP VIEW IF EXISTS $viewName');
+      if (cols.isNotEmpty) {
+        return cols;
+      }
+    } catch (_) {
+      try {
+        await _db!.execute('DROP VIEW IF EXISTS $viewName');
+      } catch (_) {}
+    }
+
+    // 2. Fallback: single-table target extraction
+    final target = SqlTableTargetExtractor.extract(trimmed);
+    if (target != null) {
+      try {
+        return await listColumnNames(table: target.tableName);
+      } catch (_) {}
+    }
+
+    return const [];
+  }
+
   /// Retrieves schema metadata and primary keys for [table].
   Future<TableSchemaMeta> getTableSchema({required String table}) async {
     final rows = await execute('PRAGMA table_info(${quoteIdentifier(table)})');

lib/features/sqlite/sqlite_sql_workspace.dart

@@ -351,6 +351,8 @@ class _SqliteSqlWorkspaceState extends material.State<SqliteSqlWorkspace> {
       final cols = <String>[];
       if (results.isNotEmpty) {
         cols.addAll(results.first.keys);
+      } else if (sqliteSqlIsReadOnlyQuery(userSql)) {
+        cols.addAll(await conn.inferQueryColumns(userSql));
       }
 
       final truncated = results.length > cap;

test/core/database/sqlite_connection_test.dart

@@ -554,5 +554,25 @@ void main() {
         'SQLite database is corrupt or not a database: /x',
       );
     });
+
+    test('inferQueryColumns returns column names when query returns zero rows', () async {
+      final conn = SqliteConnection(
+        id: 99,
+        name: 'mem',
+        path: ':memory:',
+      );
+      addTearDown(conn.disconnect);
+      await conn.connect();
+      await conn.execute('CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT, email TEXT);');
+
+      final colsAll = await conn.inferQueryColumns('SELECT * FROM users WHERE 1=0;');
+      expect(colsAll, ['id', 'name', 'email']);
+
+      final colsProjected = await conn.inferQueryColumns('SELECT id, name AS full_name FROM users WHERE id = -1;');
+      expect(colsProjected, ['id', 'full_name']);
+
+      final colsComputed = await conn.inferQueryColumns('SELECT 1 AS flag, COUNT(*) AS cnt WHERE 1=0;');
+      expect(colsComputed, ['flag', 'cnt']);
+    });
   });
 }