msyql

数据唯一性

先建立primary index或者unique index：
INSERT IGNORE
REPLACE

https://www.tutorialspoint.com/mysql/mysql-handling-duplicates.htm

https://www.mysqltutorial.org/mysql-insert-ignore/
https://www.runoob.com/mysql/mysql-handling-duplicates.html

INSERT INTO table (a,b,c) VALUES (1,2,3) ON DUPLICATE KEY UPDAT cut = cut +1

INSERT INTO books (name) SELECT ‘MySQL Manual‘ FROM dual WHERE NOT EXISTS (SELECT id FROM books WHERE id = 1)

https://blog.csdn.net/java_2017_csdn/article/details/78517789