mysql - 使用 MySQL，如何在同一个表中不存在该值的情况下插入表中？

Question

insert into student (FirstName,AGE,CITYID) values('guna','26','1')

select * from student WHERE FirstName!='guna';

此查询显示错误。我无法将 FirstName 列设为唯一。请给出除此之外的想法。

谢谢

Answer 1

INSERT INTO student ( ....)
WHERE FirstName NOT IN (SELECT FirstName FROM student)

---

修改和测试后:

INSERT INTO student 
    (FirstName, age, cityid)
SELECT 
    'guna','26','1'
FROM student -- any table name will do
WHERE 'guna' NOT IN 
(
    SELECT FirstName 
    FROM student
)
LIMIT 1 -- required because all rows will qualify if 
        -- WHERE clause is satisfied