在MYSQL / PHP中，如何从ID 1删除并将数据插入ID 5

Question

This is how my table is setup. I want to add in a new height and then delete that data at ID 1 (2.0). So it keeps leap frogging when inserting in new data. This is so I can keep up to only 5 records at a time.

Sorry, I'm very new to MYSQL/PHP.

Answer 1

Insert new data:

INSERT INTO table (height) VALUES (xxx);

Delete the pair (1,2.0):

DELETE FROM table WHERE id=1;

OR... all together like this:

UPDATE table SET height=xxx WHERE id=1;

Answer 2

for the delete, something like this might work better:

DELETE FROM table WHERE id NOT IN (SELECT ID FROM table ORDER BY ID DESC LIMIT 5)

essentially delete from the table where the id doesn't match the last 5 ids inserted. This also works when there are less than 5 entries in the database, nothing would get deleted.

Answer 3

要删除第一项，请执行以下操作：

DELETE FROM table LIMIT 1