/cte/ Recent content in CTE on 老张开工了 Hugo zh-cn Mon, 17 Feb 2025 10:00:00 +0800 /posts/2025/02/cte-and-recursive/ Mon, 17 Feb 2025 10:00:00 +0800 /posts/2025/02/cte-and-recursive/ WITH（CTE，Common Table Expression）可以让你在 SQL 中像写程序一样组织逻辑——分步骤、命名中间结果、复用。递归 CTE 更是处理层级数据的利器。 普通 CTE CTE 把复杂的查询拆成多个可读的步骤： -- 统计每个城市的客户消费情况 WITH city_stats AS ( SELECT c.city, COUNT(DISTINCT o.customer_id) AS 客户数, SUM(o.total_amount) AS 总消费 FROM customers c LEFT JOIN orders o ON c.customer_id = o.customer_id AND o.status = '已完成' GROUP BY c.city ), avg_city AS ( SELECT AVG(总消费) AS 城市平均消费 FROM city_stats ) SELECT cs.city, cs.客户数, cs.总消费, ROUND(cs.总消费 / ac.城市平均消费 * 100, 2) AS 相对占比 FROM city_stats cs CROSS JOIN avg_city ac ORDER BY cs.