要在一组固定的表中搜索，您可以使用UNION子句组合各个查询，然后添加一个硬编码的字符串来标识来源：

SELECT packaging_id AS product_id, 'packaging' AS table_name FROM packaging WHERE name = 'Cardboard box' UNION ALL SELECT stationery_id, 'stationery' FROM stationery WHERE description = 'Cardboard box' UNION ALL SELECT sales_id, 'sales' FROM sales WHERE offer = 'Cardboard box'

您需要确保结果集中每个列具有相同的数据类型，并且您可以使用第一个语句为结果集设置一个规范化的列名。