【牛客SQL必知必会 3天热身】01. 基本的检索、排序、过滤

https://www.nowcoder.com/exam/oj?page=1&tab=SQL%E7%AF%87&topicId=298
💖牛客题目， SQL必知必会。不断熟悉，不断进步，加油！👍 💬 ⭐️

题目

题目比较基础就不解析了

简单查询

# 60. 查询 cust_id 
SELECT cust_id FROM Customers

# 61. distinct 去重(必须放最前面， 表示后面参数拼接去重)
SELECT distinct prod_id FROM OrderItems

# 62. 查询所有列 *
SELECT * FROM Customers 
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排序

# 63. 对检索结果排序  orderby 字段 DESC/ASC
SELECT cust_name FROM Customers
ORDER  BY cust_name DESC

# 64. 对两个字段进行排序 (多个字段排序，逗号隔开即可)
SELECT cust_id, order_num FROM Orders
ORDER BY cust_id ASC, order_date DESC

# 65. 对两个字段排序
SELECT quantity, item_price FROM OrderItems
ORDER BY quantity DESC, item_price DESC

# 66. 检查SQL， 注意逗号和关键字等书写是否正确
SELECT vend_name
FROM Vendors 
ORDER BY vend_name DESC;
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过滤

# 67. Where 过滤数据
SELECT prod_id, prod_name FROM Products
WHERE prod_price = 9.49

# 67. Where 过滤数据， 返回某种价格的商品
SELECT prod_id, prod_name FROM Products
WHERE prod_price = 9.49

# 68. Where 过滤数据 返回价格更高的商品
SELECT prod_id, prod_name FROM Products
WHERE prod_price >= 9

# 69. where过滤 + 排序，  BETWEEN a AND b  区间 左右ab都包含
SELECT prod_name, prod_price FROM Products 
WHERE prod_price BETWEEN 3 AND 6 
ORDER BY prod_price

# 70. 分组 + 过滤 ，检索出所有总量大于100的订单  分组查询后，用HAVING聚合计算后过滤
SELECT order_num FROM OrderItems
GROUP BY order_num
HAVING SUM(quantity) > 100

# 71. 多个条件用 AND 拼接
SELECT DISTINCT vend_name FROM Vendors
WHERE vend_country = 'USA' AND vend_state = 'CA'

# 72.  in()  在这些数目范围内， in() 相当于用or = 比较  not in() 相当于用 and != 比较。 且 != null 和 == null  永远为 false 
SELECT order_num, prod_id,  quantity FROM OrderItems 
WHERE quantity >= 100 AND prod_id in('BR01', 'BR02', 'BR03')

# 73. AND 拼接条件 + 排序
SELECT prod_name, prod_price FROM Products
WHERE prod_price >= 3 AND prod_price <= 6
ORDER BY prod_price ASC

# 74. SQL 纠错， 注意各个关键字的位置 和 标点符号
SELECT vend_name 
FROM Vendors 
WHERE vend_country = 'USA' AND vend_state = 'CA'
ORDER BY vend_name 
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知识点

DISTINCT

distinct 用法 https://blog.csdn.net/shenziheng1/article/details/102536146

WHERE 和 HAVING 的区别？

in() 和 not in() 中有 null 的坑

SQL避坑：当in，not in遇上null这种坑你避过吗？https://blog.csdn.net/godlovedaniel/article/details/125376244
in() 相当于用 or = 比较
not in() 相当于用 and != 比较。
且 != null 和 == null 永远为 false
以此就可以发现 not in() 如果里面有 null 的话， 一定返回false， 所有条件都不满足