Multiple Updates in MySQL

Question

I know that you can insert multiple rows at once, is there a way to update multiple rows at once (as in, in one query) in MySQL?

Edit: For example I have the followi

Answer 1

You can alias the same table to give you the id's you want to insert by (if you are doing a row-by-row update:

UPDATE table1 tab1, table1 tab2 -- alias references the same table
SET 
col1 = 1
,col2 = 2
. . . 
WHERE 
tab1.id = tab2.id;

Additionally, It should seem obvious that you can also update from other tables as well. In this case, the update doubles as a "SELECT" statement, giving you the data from the table you are specifying. You are explicitly stating in your query the update values so, the second table is unaffected.

Answer 2

UPDATE table1, table2 SET table1.col1='value', table2.col1='value' WHERE table1.col3='567' AND table2.col6='567'

This should work for ya.

There is a reference in the MySQL manual for multiple tables.

Answer 3

UPDATE `your_table` SET 

`something` = IF(`id`="1","new_value1",`something`), `smth2` = IF(`id`="1", "nv1",`smth2`),
`something` = IF(`id`="2","new_value2",`something`), `smth2` = IF(`id`="2", "nv2",`smth2`),
`something` = IF(`id`="4","new_value3",`something`), `smth2` = IF(`id`="4", "nv3",`smth2`),
`something` = IF(`id`="6","new_value4",`something`), `smth2` = IF(`id`="6", "nv4",`smth2`),
`something` = IF(`id`="3","new_value5",`something`), `smth2` = IF(`id`="3", "nv5",`smth2`),
`something` = IF(`id`="5","new_value6",`something`), `smth2` = IF(`id`="5", "nv6",`smth2`) 

// You just building it in php like

$q = 'UPDATE `your_table` SET ';

foreach($data as $dat){

  $q .= '

       `something` = IF(`id`="'.$dat->id.'","'.$dat->value.'",`something`), 
       `smth2` = IF(`id`="'.$dat->id.'", "'.$dat->value2.'",`smth2`),';

}

$q = substr($q,0,-1);

So you can update hole table with one query

Answer 4

You may also be interested in using joins on updates, which is possible as well.

Update someTable Set someValue = 4 From someTable s Inner Join anotherTable a on s.id = a.id Where a.id = 4
-- Only updates someValue in someTable who has a foreign key on anotherTable with a value of 4.

Edit: If the values you are updating aren't coming from somewhere else in the database, you'll need to issue multiple update queries.

Answer 5

Why does no one mention multiple statements in one query?

In php, you use multi_query method of mysqli instance.

From the php manual

MySQL optionally allows having multiple statements in one statement string. Sending multiple statements at once reduces client-server round trips but requires special handling.

Here is the result comparing to other 3 methods in update 30,000 raw. Code can be found here which is based on answer from @Dakusan

Transaction: 5.5194580554962
Insert: 0.20669293403625
Case: 16.474853992462
Multi: 0.0412278175354

As you can see, multiple statements query is more efficient than the highest answer.

If you get error message like this:

PHP Warning:  Error while sending SET_OPTION packet

You may need to increase the max_allowed_packet in mysql config file which in my machine is /etc/mysql/my.cnf and then restart mysqld.