sql - 计数空记录不起作用

Question

create table scoda(product varchar(25),price int,sale varchar(23))
insert into scoda values('watch',10,6)
insert into scoda values('socks',8,'NULL')

SELECT COUNT(*) AS GK FROM scoda WHERE sale IS NULL

---

Expected output:1
Actual output:0

需要帮助才能继续我是 sql 的初学者

Answer 1

利用

insert into scoda values('socks',8,NULL)

（不带引号）。

Answer 2

问题出在插入语句中：

insert into scoda values('socks',8,NULL)