I have a query like this
SET #update_id := 0;
UPDATE table SET column = something, id = (SELECT #update_id := id)
WHERE condition
LIMIT 1;
SELECT #update_id;
It's supposed to update a column and return the updated row's id. and as you can see I don't have the id of the row before executing the query.
I'm using pdo, Is there any way to fetch the value of #updated_id in php?
I get SQLSTATE[HY000]: General error when I'm trying to use $stmt->fetchColumn();.
also I'm sure the query is correct cause I executed it in phpMyadmin and it returned a correct value so it's working. the result in phpMyadmin was like below:
| #updated_id |
|------------------|
| 32 |
and the desired column in the row with the id of 32 (which had the conditions) was updated.
any thoughts?
I think you can read this value as you read simple table. You also can add field alias and read this field by name - SELECT #update_id AS updated_id.
Another variant is to use SELECT...FOR UPDATE statement.
Related
I have tried to set the max value for the particular column but that is not working for me. I do not know where i'm going wrong.
UPDATE `upload_video`
SET order_id ='select max(order_id)+1
FROM upload_video'
WHERE `video_id` = 22
This is my query i run the select max(order_id)+1 from upload_video query separately which is giving the result. But if i use this query in update query, the query is executing without error. But the order_id is not updating properly. please help me
Your query is almost correct in standard SQL, you only need to use brackets () instead of apostrophe ':
SET order_id = (SELECT MAX(...) ...)
but MySQL doesn't allow you to update a table while selecting from the same table, a workaround is to use a subquery that calculates the value that you need, and to join your subquery with the table you need to update:
UPDATE
upload_video JOIN (SELECT COALESCE(MAX(order_id),0)+1 max_id
FROM upload_video) s
SET
upload_video.order_id=s.max_id
WHERE
video_id=22
Please see fiddle here.
You have a typo in the statement, you used UPADTE instead of UPDATE.
One problem is, don't quote the subquery. You have used single quotes, which means the expression select max(order_id)+1... was interpreted as a text literal (a varchar). But you clearly don't want that (I guess order_id is a number). What you want instead is to evaluate the subquery. However, if you try:
UPDATE `upload_video`
SET order_id =(select max(order_id)+1
FROM upload_video)
WHERE `video_id` = 22
then MySQL doesn't allow it (I didn't know about that). Other databases such as PostgreSQL allow it. So you might need two statements:
select #id = coalesce(max(order_id), 0) + 1 FROM upload_video;
UPDATE `upload_video` SET order_id = #id WHERE `video_id` = 22;
Please note this works in MySQL but not in other databases.
Try this:
UPDATE `upload_video`
SET order_id =(select COALESCE(max(U2.order_id),0)+1
FROM upload_video U2)
WHERE `video_id` = 22
Peraphs this query goes in error because MySql doesn't want to use the same table in UPDATE and in subquery.
If your case please write two queries.
The first get the maximum value, the second does update
Just working with a database and some tests were done recently which checked the integrity of the setup.
As a result, a lot of test entries were added which were then deleted. However, when new entries are added, the ID number value continues from after the entries added.
What I want:
ID increases by one from where it left off before the additional rows were added:
4203, 4204, 4205, 4206 etc.
What is happening:
ID increases by one from after the additional rows ID:
4203, 4204, 6207, 6208 6209 etc.
Not sure where to fix this...whether in phpmyadmin or in the PHP code. Any help would be appreciated. Thanks!
I have ran into this before and I solve it easily with phpMyAdmin. Select the database, select the table, open the operations tab, and in the Table Options set the AUTO_INCREMENT to 1 then click GO. This will force mysql to look for the last auto incremented value and then set it to the value directly after that. I do this on a manually basis that way I know that when a row is skipped that it was not from testing but a deletion because when I test and delete the rows I fix the AI value.
I don't think there's a way to do this with an auto-incrementing ID key.
You could probably do it by assigning the ID to (select max(id) + 1 from the_table)
You could drop the primary key then recreate it, but this would reassign all the existing primary keys so could cause issues with relationships (although if you don't have any gaps in your primary key you may get away with it).
I would however say that you should accept (and your app should reflect) the possibility of missing IDs. For example in a web app if someone links to a missing ID you would want a 404 returned not a different record.
There should be no need to "reset" the id values; I concur with the other comments concerning this issue.
The behavior you observe with AUTO_INCREMENT is by design; it is described in the MySQL documentation.
With all that said, I will describe an approach you can use to change the id values of those rows "downwards", and make them all contiguous:
As a "stepping stone" first step, we will create a query that gets a list of the id values that we need changed, along with a proposed new id value we are going to change it to. This query makes use of a MySQL user variable.
Assuming that 4203 is the id value you want to leave as is, and you want the next higher id value to be reset to 4204, the next higher id to be reset to 4205, etc.
SELECT s.id
, #i := #i + 1 AS new_id
FROM mytable s
JOIN (SELECT #i := 4203) i
WHERE s.id > 4203
ORDER BY s.id
(Note: the constant value 4203 appears twice in the query above.)
Once we're satisfied that this query is working, and returning the old and new id values, we can use this query as an inline view (MySQL calls it a derived table), in a multi-table UPDATE statement. We just wrap that query in a set of parentheses, and give assign it an alias, so we can reference it like a regular table. (In an inline view, MySQL actually materializes the resultset returned by the query into a MyISAM table, which probably explains why MySQL refers to it as a "derived table".)
Here's an example UPDATE statement that references the derived table:
UPDATE ( SELECT s.id
, #i := #i + 1 AS new_id
FROM mytable s
JOIN (SELECT #i := 4203) i
WHERE s.id > 4203
ORDER BY s.id
) n
JOIN mytable t
ON t.id = n.id
SET t.id = n.new_id
ORDER BY t.id
Note that the old id value from the inline view is matched to the id value in the existing table (the ON clause), and the "new_id" value generated by the inline view is assigned to the id column (the SET clause.)
Once the id values are assigned, we can reset the AUTO_INCREMENT value on the table:
ALTER TABLE mytable AUTO_INCREMENT = 1;
NOTE: this is just an example, and is provided with the caveat that this should not be necessary to reassign id values. Ideally, primary key values should be IMMUTABLE i.e. they should not change once they have been assigned.
I have the following database table.
id article_content article_views
1 content.. 48
I am trying to increase the value of the column article_views using mysql query.
I know I can fetch the number and then add +1 and then update the value, but is there any better way to do this?
Thanks :)
Your query becomes -
Update TABLE_NAME SET article_views = article_views+1 WHERE id = 'your_id'
I need to get next id from table (auto_increment).
I could just use SELECT * from table ORDER BY id DESC LIMIT 1;
For example I get 50. But if we delete from table two items I will get 48 but correct one
will be 51. How get correct value even we something delete from table ?
You can only use SHOW TABLE STATUS LIKE 'tablename' to fetch the auto_increment value. A simpler solution might be: SELECT MAX(id) + 1 FROM table, but this is buggy if the last entry was deleted.
show table status like 'table_name'
next id value is in 'Auto_increment' field
SHOW TABLE STATUS LIKE 'table'
The value you want is in the Auto_increment field.
Be careful about concurrency though: by the time you get around to using this value, some other client could have inserted into the table and thus your value is out of date. It's usually best to try to not need this.
SELECT LAST_INSERT_ID() + 1;
gets the last ID used in an insert in an autoincrement column + 1
I see two solutions for the next ID:
1) Select bigger value of a column with max function. Example: select max( id ) from table;
2) Using the command SHOW STATUS LIKE and get the correct index of array. Take a look: http://dev.mysql.com/doc/refman/5.1/en/show-table-status.html
Seems to me you're creating a race condition here.
Why exactly can you not insert the row you want to insert and then use LAST_INSERT_ID() to find it's ID?
How do I get the ID of the last updated row in MySQL using PHP?
I've found an answer to this problem :)
SET #update_id := 0;
UPDATE some_table SET column_name = 'value', id = (SELECT #update_id := id)
WHERE some_other_column = 'blah' LIMIT 1;
SELECT #update_id;
EDIT by aefxx
This technique can be further expanded to retrieve the ID of every row affected by an update statement:
SET #uids := null;
UPDATE footable
SET foo = 'bar'
WHERE fooid > 5
AND ( SELECT #uids := CONCAT_WS(',', fooid, #uids) );
SELECT #uids;
This will return a string with all the IDs concatenated by a comma.
Hm, I am surprised that among the answers I do not see the easiest solution.
Suppose, item_id is an integer identity column in items table and you update rows with the following statement:
UPDATE items
SET qwe = 'qwe'
WHERE asd = 'asd';
Then, to know the latest affected row right after the statement, you should slightly update the statement into the following:
UPDATE items
SET qwe = 'qwe',
item_id=LAST_INSERT_ID(item_id)
WHERE asd = 'asd';
SELECT LAST_INSERT_ID();
If you need to update only really changed row, you would need to add a conditional update of the item_id through the LAST_INSERT_ID checking if the data is going to change in the row.
This is officially simple but remarkably counter-intuitive. If you're doing:
update users set status = 'processing' where status = 'pending'
limit 1
Change it to this:
update users set status = 'processing' where status = 'pending'
and last_insert_id(user_id)
limit 1
The addition of last_insert_id(user_id) in the where clause is telling MySQL to set its internal variable to the ID of the found row. When you pass a value to last_insert_id(expr) like this, it ends up returning that value, which in the case of IDs like here is always a positive integer and therefore always evaluates to true, never interfering with the where clause. This only works if some row was actually found, so remember to check affected rows. You can then get the ID in multiple ways.
MySQL last_insert_id()
You can generate sequences without calling LAST_INSERT_ID(), but the
utility of using the function this way is that the ID value is
maintained in the server as the last automatically generated value. It
is multi-user safe because multiple clients can issue the UPDATE
statement and get their own sequence value with the SELECT statement
(or mysql_insert_id()), without affecting or being affected by other
clients that generate their own sequence values.
MySQL mysql_insert_id()
Returns the value generated for an AUTO_INCREMENT column by the
previous INSERT or UPDATE statement. Use this function after you have
performed an INSERT statement into a table that contains an
AUTO_INCREMENT field, or have used INSERT or UPDATE to set a column
value with LAST_INSERT_ID(expr).
The reason for the differences between LAST_INSERT_ID() and
mysql_insert_id() is that LAST_INSERT_ID() is made easy to use in
scripts while mysql_insert_id() tries to provide more exact
information about what happens to the AUTO_INCREMENT column.
PHP mysqli_insert_id()
Performing an INSERT or UPDATE statement using the LAST_INSERT_ID()
function will also modify the value returned by the mysqli_insert_id()
function.
Putting it all together:
$affected_rows = DB::getAffectedRows("
update users set status = 'processing'
where status = 'pending' and last_insert_id(user_id)
limit 1"
);
if ($affected_rows) {
$user_id = DB::getInsertId();
}
(FYI that DB class is here.)
This is the same method as Salman A's answer, but here's the code you actually need to do it.
First, edit your table so that it will automatically keep track of whenever a row is modified. Remove the last line if you only want to know when a row was initially inserted.
ALTER TABLE mytable
ADD lastmodified TIMESTAMP
DEFAULT CURRENT_TIMESTAMP
ON UPDATE CURRENT_TIMESTAMP;
Then, to find out the last updated row, you can use this code.
SELECT id FROM mytable ORDER BY lastmodified DESC LIMIT 1;
This code is all lifted from MySQL vs PostgreSQL: Adding a 'Last Modified Time' Column to a Table and MySQL Manual: Sorting Rows. I just assembled it.
Query :
$sqlQuery = "UPDATE
update_table
SET
set_name = 'value'
WHERE
where_name = 'name'
LIMIT 1;";
PHP function:
function updateAndGetId($sqlQuery)
{
mysql_query(str_replace("SET", "SET id = LAST_INSERT_ID(id),", $sqlQuery));
return mysql_insert_id();
}
It's work for me ;)
SET #uids := "";
UPDATE myf___ingtable
SET id = id
WHERE id < 5
AND ( SELECT #uids := CONCAT_WS(',', CAST(id AS CHAR CHARACTER SET utf8), #uids) );
SELECT #uids;
I had to CAST the id (dunno why)... or I cannot get the #uids content (it was a blob)
Btw many thanks for Pomyk answer!
Hey, I just needed such a trick - I solved it in a different way, maybe it'll work for you. Note this is not a scalable solution and will be very bad for large data sets.
Split your query into two parts -
first, select the ids of the rows you want to update and store them in a temporary table.
secondly, do the original update with the condition in the update statement changed to where id in temp_table.
And to ensure concurrency, you need to lock the table before this two steps and then release the lock at the end.
Again, this works for me, for a query which ends with limit 1, so I don't even use a temp table, but instead simply a variable to store the result of the first select.
I prefer this method since I know I will always update only one row, and the code is straightforward.
ID of the last updated row is the same ID that you use in the 'updateQuery' to found & update that row. So, just save(call) that ID on anyway you want.
last_insert_id() depends of the AUTO_INCREMENT, but the last updated ID not.
My solution is , first decide the "id" ( #uids ) with select command and after update this id with #uids .
SET #uids := (SELECT id FROM table WHERE some = 0 LIMIT 1);
UPDATE table SET col = 1 WHERE id = #uids;SELECT #uids;
it worked on my project.
Further more to the Above Accepted Answer
For those who were wondering about := & =
Significant difference between := and =, and that is that := works as a variable-assignment operator everywhere, while = only works that way in SET statements, and is a comparison operator everywhere else.
So SELECT #var = 1 + 1; will leave #var unchanged and return a boolean (1 or 0 depending on the current value of #var), while SELECT #var := 1 + 1; will change #var to 2, and return 2.
[Source]
If you are only doing insertions, and want one from the same session, do as per peirix's answer. If you are doing modifications, you will need to modify your database schema to store which entry was most recently updated.
If you want the id from the last modification, which may have been from a different session (i.e. not the one that was just done by the PHP code running at present, but one done in response to a different request), you can add a TIMESTAMP column to your table called last_modified (see http://dev.mysql.com/doc/refman/5.1/en/datetime.html for information), and then when you update, set last_modified=CURRENT_TIME.
Having set this, you can then use a query like:
SELECT id FROM table ORDER BY last_modified DESC LIMIT 1;
to get the most recently modified row.
No need for so long Mysql code. In PHP, query should look something like this:
$updateQuery = mysql_query("UPDATE table_name SET row='value' WHERE id='$id'") or die ('Error');
$lastUpdatedId = mysql_insert_id();