Question: What is the easiest way to update many rows in a table? I have a csv file that looks like this:

```
|primary_key |value|
|          1 |  xyz|
|          2 |  abc|
|          3 |  def|
...

```

Rows with these primary keys already exist in the target table 

I would like to update the target table with these values. Is there syntax so that I can write something like:

```
update mytable set value = ('xyz', 'abc', 'def') where primary key = (1,2,3);

```

Looking through the [MySQL Update Reference](http://dev.mysql.com/doc/refman/5.0/en/update.html), this site ([MySQL - csv update](https://dba.stackexchange.com/q/11811/1580)), SO ([update multiple rows](https://stackoverflow.com/questions/184096/update-multiple-rows-into-sql-table), [multiple db updates](https://stackoverflow.com/questions/184471/multiple-db-updates), [update multiple rows](https://stackoverflow.com/questions/1305863/update-multiple-rows)), I suspect that the answer is "no", but I'd like to confirm that this is true.

Answer: 
First here is sample data

```
mysql> drop table if exists mytable;
Query OK, 0 rows affected (0.03 sec)

mysql> create table mytable
    -> (
    ->     id int not null,
    ->     value VARCHAR(255),
    ->     primary key (id)
    -> );
Query OK, 0 rows affected (0.06 sec)

mysql> insert into mytable (id) values (1),(2),(3);
Query OK, 3 rows affected (0.06 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select * from mytable;
+----+-------+
| id | value |
+----+-------+
|  1 | NULL  |
|  2 | NULL  |
|  3 | NULL  |
+----+-------+
3 rows in set (0.00 sec)

mysql>

```

Here is the new query

```
update mytable A inner join
(
    SELECT 1 id,'xyz' value UNION
    SELECT 2   ,'abc'       UNION
    SELECT 3   ,'def'

) B USING (id)
SET A.value = B.value;

```

Here is the new query executed

```
mysql> update mytable A inner join
    -> (
    ->     SELECT 1 id,'xyz' value UNION
    ->     SELECT 2   ,'abc'       UNION
    ->     SELECT 3   ,'def'
    -> ) B USING (id)
    -> SET A.value = B.value;
Query OK, 0 rows affected (0.06 sec)
Rows matched: 3  Changed: 0  Warnings: 0

mysql> select * from mytable;
+----+-------+
| id | value |
+----+-------+
|  1 | xyz   |
|  2 | abc   |
|  3 | def   |
+----+-------+
3 rows in set (0.00 sec)

mysql>

```
Assuming that you don't want to load the data from the CSV file into a database table and then do a correlated `UPDATE`, 

```
UPDATE mytable t
   SET value = (SELECT value
                  FROM tbl_with_csv_data csv
                 WHERE csv.primary_key = t.primary_key)
 WHERE EXISTS( SELECT 1
                 FROM tbl_with_csv_data csv
                 WHERE csv.primary_key = t.primary_key)

```

then you should be able to use a `CASE`

```
UPDATE mytable t
   SET value = CASE WHEN primary_key = 1 THEN 'xyz'
                    WHEN primary_key = 2 THEN 'abc'
                    WHEN primary_key = 3 THEN 'def'
                    ELSE value
                END
 WHERE primary_key IN (1,2,3);

```