Postage SQL 是一個用于處理郵政數據的 SQL 數據庫。以下是一個簡單的示例，展示了如何編寫 Postage SQL 查詢。假設我們有一個名為 postal_data 的表，其中包含以下列：id, sender_id, receiver_id, weight, size, country, postage_cost。
SELECT * FROM postal_data;
SELECT * FROM postal_data WHERE sender_id = 'sender123';
SELECT * FROM postal_data WHERE receiver_id = 'receiver456';
SELECT * FROM postal_data WHERE weight > 100;
SELECT * FROM postal_data WHERE size = 'A4';
SELECT * FROM postal_data WHERE country = 'China' AND sender_id IN (SELECT id FROM postal_data WHERE country = 'China') AND receiver_id IN (SELECT id FROM postal_data WHERE country = 'China');
SELECT * FROM postal_data WHERE postage_cost > 5;
這些示例展示了如何使用基本的 SQL 查詢操作符（如 SELECT, FROM, WHERE, AND, OR）編寫 Postage SQL 查詢。根據實際需求，您可能需要編寫更復雜的查詢。
