MySQL insert \ pre update + judgment condition

1、mysql Operation to determine whether data exists before inserting

INSERT INTO table(field1, field2, fieldn) SELECT 'field1',

'field2', 'fieldn' FROM DUAL WHERE NOT EXISTS(SELECT field FROM

table WHERE field = ?)

2、 Insert if it doesn't exist , If it exists, it will be updated

If the inserted data will cause UNIQUE Index or PRIMARY KEY conflict / repeat , execute UPDATE sentence

INSERT INTO `student`(`name`, `age`) VALUES('Jack', 19)

ON DUPLICATE KEY

UPDATE `age`=19; 

-- If will happen conflict, the update statement is executed 2 row(s) affected

3、 If the inserted data will cause UNIQUE Index or PRIMARY KEY conflict / repeat , Delete the old data first and then insert the latest data

REPLACE INTO `student`(`name`, `age`) VALUES('Jack', 18);

4、 Avoid repeated insertion

keyword / sentence ：insert ignore into, If the inserted data will cause UNIQUE Index or PRIMARY KEY conflict / repeat , Ignore this operation / Don't insert data

INSERT IGNORE INTO `student`(`name`, `age`) VALUES('Jack', 18);

-- 0 row(s) affected