Update Thousands of Record

[lilmer]

Hello, 

 

Anyone can suggest me what is the best way to update table records. I'm kinda scared to make an update on a table because it may damage the system and I am not really good on SQL commands.

 

Right now I just made a process on PHP to update table records. It does update email records on but it stop because of the limit of loading the page. Is there anyway accurately update all the data of the table.

 

Here is what I want to achieve.

 

I have a table with an "email" field on it, those email data from  "email" field on tb_one must be change to cID records base on tb_two. 

 

tb_one 

Field =

  - id

  - email

  - etc.

 

tb_two

Field = 

  - id

  - email (same as on tb_one)

  - cID

 

[jazzman1]

A common, standard sql way of doing this is:

UPDATE tbl_one t1 
SET t1.email = (SELECT t2.email FROM tbl_two t2 WHERE t1.id = t2.cID)
WHERE EXISTS (SELECT 1 FROM tbl_two t2 WHERE t1.id = t2.cID)

PS - Don't forget to backup your data before trying this ( for every case)

Edited September 10, 2014 by jazzman1

[Barand]

This should be more efficient than using dependent subqueries

UPDATE tb_one t1
INNER JOIN tb_two t2 ON t1.id = t2.cID
SET t1.email = t2.email

[lilmer]

Thank you people, I'd just try this using my navicat, works perfect.