使用PHP / MySQL循环更新当前行

Question

I have a MySQL table with over 16 million rows and there is no primary key. Whenever I try to add one, my connection crashes. I have tried adding one as an auto increment in PHPMyAdmin and in command line but the connection is always lost after about 10 minutes.

What I would like to do is loop through the table's rows in PHP so I can limit the number of results and with each returned row add an auto-incremented ID number. Since the number of impacted rows would be reduced by reducing the load on the MySQL query, I won't lose my connection.

I want to do something like

SELECT * FROM MYTABLE LIMIT 1000001, 2000000;

Then, in the loop, update the current row

UPDATE (current row) SET ID='$i++'

How do I do this?

I am open to a MySQL solution as well. I just need a process that will not cause me to lose my MySQL connection

Note: the original data was given to me as a txt file. I don't know if there are duplicates but I cannot eliminate any rows. Also, no rows will be added. This table is going to be used only for querying purposes. When I have added indexes, however, there were no problems.

Answer 1

It is easier

ALTER TABLE table_name MODIFY COLUMN id INT NOT NULL AUTO_INCREMENT PRIMARY KEY

In case you want to remove the primary key after the modification

ALTER TABLE table_name MODIFY COLUMN id INT

Answer 2

I would avoid setting primary keys manually. Much safer to let MySQL do it. You can temporarily increase the timeout in the config file:

wait_timeout = 28800
interactive_timeout = 28800