更新时间:2025-03-24 12:28:20
小伙伴们,今天来聊聊SQL中的判断语句和多表查询技巧!😎首先,SQL中的判断语句(如`CASE WHEN`)是实现数据筛选和分类的好帮手。比如:
```sql
SELECT
product_name,
CASE
WHEN price > 100 THEN '高价'
WHEN price BETWEEN 50 AND 100 THEN '中价'
ELSE '低价'
END AS price_level
FROM products;
```
这个例子中,我们通过`CASE WHEN`将商品价格分为三档,清晰明了!
接着,咱们再聊聊多表查询!💡假设你有两个表`orders`和`customers`,想找出每个客户的订单数量,可以用`JOIN`连接两表:
```sql
SELECT
c.customer_name,
COUNT(o.order_id) AS order_count
FROM customers c
LEFT JOIN orders o ON c.customer_id = o.customer_id
GROUP BY c.customer_name;
```
这样就能轻松统计每位客户下单情况啦!📊
掌握这些技能,数据库操作so easy!💪✨