UPDATE multiple rows with different values in one query in MySQL - mysql

Question

I am trying to understand how to UPDATE multiple rows with different values and I just don't get it. The solution is everywhere but to me it looks difficult to understand.
For instance, three updates into 1 query:
UPDATE table_users
SET cod_user = '622057'
, date = '12082014'
WHERE user_rol = 'student'
AND cod_office = '17389551';
UPDATE table_users
SET cod_user = '2913659'
, date = '12082014'
WHERE user_rol = 'assistant'
AND cod_office = '17389551';
UPDATE table_users
SET cod_user = '6160230'
, date = '12082014'
WHERE user_rol = 'admin'
AND cod_office = '17389551';
I read an example, but I really don't understand how to make the query. i.e:
UPDATE table_to_update
SET cod_user= IF(cod_office = '17389551','622057','2913659','6160230')
,date = IF(cod_office = '17389551','12082014')
WHERE ?? IN (??) ;
I'm not entirely clear how to do the query if there are multiple condition in the WHERE and in the IF condition..any ideas?

Answer 1

You can do it this way:
UPDATE table_users
SET cod_user = (case when user_role = 'student' then '622057'
when user_role = 'assistant' then '2913659'
when user_role = 'admin' then '6160230'
end),
date = '12082014'
WHERE user_role in ('student', 'assistant', 'admin') AND
cod_office = '17389551';
I don't understand your date format. Dates should be stored in the database using native date and time types.

Answer 2

MySQL allows a more readable way to combine multiple updates into a single query. This seems to better fit the scenario you describe, is much easier to read, and avoids those difficult-to-untangle multiple conditions.
INSERT INTO table_users (cod_user, date, user_rol, cod_office)
VALUES
('622057', '12082014', 'student', '17389551'),
('2913659', '12082014', 'assistant','17389551'),
('6160230', '12082014', 'admin', '17389551')
ON DUPLICATE KEY UPDATE
cod_user=VALUES(cod_user), date=VALUES(date)
This assumes that the user_rol, cod_office combination is a primary key. If only one of these is the primary key, then add the other field to the UPDATE list.
If neither of them is a primary key (that seems unlikely) then this approach will always create new records - probably not what is wanted.
However, this approach makes prepared statements easier to build and more concise.

Answer 3

UPDATE table_name
SET cod_user =
CASE
WHEN user_rol = 'student' THEN '622057'
WHEN user_rol = 'assistant' THEN '2913659'
WHEN user_rol = 'admin' THEN '6160230'
END, date = '12082014'
WHERE user_rol IN ('student','assistant','admin')
AND cod_office = '17389551';

Answer 4

You can use a CASE statement to handle multiple if/then scenarios:
UPDATE table_to_update
SET cod_user= CASE WHEN user_rol = 'student' THEN '622057'
WHEN user_rol = 'assistant' THEN '2913659'
WHEN user_rol = 'admin' THEN '6160230'
END
,date = '12082014'
WHERE user_rol IN ('student','assistant','admin')
AND cod_office = '17389551';

Answer 5

To Extend on #Trevedhek answer,
In case the update has to be done with non-unique keys, 4 queries will be need
NOTE: This is not transaction-safe
This can be done using a temp table.
Step 1: Create a temp table keys and the columns you want to update
CREATE TEMPORARY TABLE temp_table_users
(
cod_user varchar(50)
, date varchar(50)
, user_rol varchar(50)
, cod_office varchar(50)
) ENGINE=MEMORY
Step 2: Insert the values into the temp table
Step 3: Update the original table
UPDATE table_users t1
JOIN temp_table_users tt1 using(user_rol,cod_office)
SET
t1.cod_office = tt1.cod_office
t1.date = tt1.date
Step 4: Drop the temp table

Answer 6

In php, you use multi_query method of mysqli instance.
$sql = "SELECT COUNT(*) AS _num FROM test;
INSERT INTO test(id) VALUES (1);
SELECT COUNT(*) AS _num FROM test; ";
$mysqli->multi_query($sql);
comparing result to transaction, insert, case methods in update 30,000 raw.
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.
Just in case 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.

Answer 7

UPDATE Table1 SET col1= col2 FROM (SELECT col2, col3 FROM Table2) as newTbl WHERE col4= col3
Here col4 & col1 are in Table1. col2 & col3 are in Table2 I Am trying to update each col1 where col4 = col3 different value for each row

Answer 8

I did it this way:
<update id="updateSettings" parameterType="PushSettings">
<foreach collection="settings" item="setting">
UPDATE push_setting SET status = #{setting.status}
WHERE type = #{setting.type} AND user_id = #{userId};
</foreach>
</update>
where PushSettings is
public class PushSettings {
private List<PushSetting> settings;
private String userId;
}
it works fine