Mysql in PHP - how to update only one row in table

问题:

I am trying to update fields in my DB, but got stuck with such a simple problem: I want to update just one row in the table with the biggest id number. I would do something like that:

UPDATE table SET name='test_name' WHERE id = max(id)

Unfortunatelly it doesnt work. Any ideas?

Table Structure

id | name
---|------
 1 | ghost
 2 | fox
 3 | ghost

I want to update only last row because ID number is the greatest one.

回答1:

Select the max id first, then update.

UPDATE table SET name='test_name' WHERE id = (SELECT max(id) FROM table)

回答2:

The use of MAX() is not possible at this position. But you can do this:

UPDATE table SET name='test_name' ORDER BY id DESC LIMIT 1;

回答3:

I think iblue's method is probably your best bet; but another solution might be to set the result as a variable, then use that variable in your UPDATE statement.

SET @max = (SELECT max(`id`) FROM `table`);
UPDATE `table` SET `name` = "FOO" WHERE `id` = @max;

This could come in handy if you're expecting to be running multiple queries with the same ID, but its not really ideal to run two queries if you're only performing one update operation.

回答4:

UPDATE table SET name='test_name' WHERE id = (SELECT max(id) FROM table) 

This query will return an error as you can not do a SELECT subquery from the same table you're updating.

Try using this:

UPDATE table SET name='test_name' WHERE id = (
    SELECT uid FROM (
        SELECT MAX(id) FROM table AS t
    ) AS tmp
)

This creates a temporary table, which allows using same table for UPDATE and SELECT, but at the cost of performance.

回答5:

UPDATE table_NAME
SET COLUMN_NAME='COLUMN_VALUE' 
ORDER BY ID 
DESC LIMIT 1;

Because you can't use SELECT IN DELETE OR UPDATE CLAUSE.ORDER BY ID DESC LIMIT 1. This gives you ID's which have maximum value MAX(ID) like you tried to do. But MAX(ID) will not work.

回答6:

Old Question, but for anyone coming across this you might also be able to do this:

UPDATE
     `table_name` a
JOIN (SELECT MAX(`id`) AS `maxid` FROM `table_name`) b ON (b.`maxid` = a.`id`)
SET a.`name` = 'test_name';

回答7:

We can update the record using max() function and maybe it will help for you.

 UPDATE MainTable
 SET [Date] = GETDATE()
 where [ID] = (SELECT MAX([ID]) FROM MainTable)

It will work the perfect for me.

回答8:

Using PHP I tend to do run a mysqli_num_rows then put the result into a variable, then do an UPDATE statement saying where ID = the newly created variable. Some people have posted there is no need to use LIMIT 1 on the end however I like to do this as it doesn't cause any trivial delay but could prevent any unforeseen actions from being taken.

If you have only just inserted the row you can use PHP's mysqli_insert_id function to return this id automatically to you without needing to run the mysqli_num_rows query.