I have a very simple SELECT looking like this:
SELECT path FROM items WHERE id = 17
Now in the table items there is also a column count, which I want to have incremented everytime the above query is executed.
What is the optimal way to do this?
There is no way to do that in same query.
You can do something like this:
START TRANSACTION;
UPDATE ....
SELECT ....
COMMIT;
You need to create a stored procedure and then create an atomic transaction using
START TRANSACTION;
UPDATE items set count = (SELECT MAX(count)+1 from items);
SELECT path FROM items WHERE id = 17;
COMMIT;
try combining the update and select into a single call, the response from the SELECT should be returned
UPDATE items SET count = count + 1; SELECT path FROM items WHERE id = 17
Related
I'm running a query to select an array of id's from one table, so that I can update another table with the data from the resulting dataset.
//db query result
$query = "SELECT image_id FROM jos_jxgallery_images ORDER BY jos_jxgallery_images.image_id DESC LIMIT 25";
$query_execute = mysql_query($query);
mysql_close($db_config);
while ($items = mysql_fetch_array($query_execute)) {
echo $items['image_id'];
echo '<br/>';
}
I think I need to do it in the while loop, I just have the echo there to see what's in items variable. That works ok. I think the thing to do is in the while loop..I'd like to replace the 'echoing' with an actual update SET query for my other table. Something like...
while ($items = mysql_fetch_array($query_execute)) {
$q = "UPDATE jx_gallery_images_ratings SET image_id ='".$items."";
mysql_query($q);
But the new table has no data. Is there just a better way to write this...maybe even as one query or something? Any help is appreciated.
EDIT: I should explain a little better. The table is empty, and I could go ahead and use an insert from one table to another just to get the id's there. However, after that...in a way it is somewhat a 'temp' table. But not really. Whatever ordering of image_id's I have created in my SELECT query from my first table (There are other rows to sort by other than image_id, like 'hits', for example)...so the second table needs to be updated with the same ordering of image_id's. Probably be running this several little snippet several times with a cron job. So, yeah, I'm trying to update the second table with the ordering of the SELECT query of the first table and just put the id's in my second table, again...according to the order of the first SELECT query.
If the table is empty, you should do an insert. You can do it in a single query like this:
INSERT INTO jx_gallery_images_ratings (image_id)
SELECT image_id FROM jos_jxgallery_images ORDER BY jos_jxgallery_images.image_id DESC LIMIT 25
Note that you probably wouldn't really need the ORDER BY, adn you could do it for all images at once by removing the LIMIT
Something like:
UPDATE tbl_updateme SET row_to_update = (SELECT row_you_need from tbl_target WHERE tbl_updateme.comparison_row = tbl_target.comparison_row)
INSERT INTO jx_gallery_images_ratings (image_id) (SELECT image_id FROM jos_jxgallery_images ORDER BY jos_jxgallery_images.image_id DESC LIMIT 25)
Or
Easy way is create trigger that updates table after selection with Dynamic SQL
How to receive the last row id in the database without generating a new row or updating the row.
Just to read the last id?
I have the function mysql_insert_id and need something like this, but without generating a new row.
SELECT MAX(id) AS latest_id
FROM table_name
If you instead want the comming (and not yet existing) id without inserting a row, see my previous answer.
You need to use max() function like
select max(yourcol) from yourtable
You can try lot of queries for that :-
select * from TABLE_NAME order by ID desc limit 1;
"or"
SELECT *
FROM TABLE
WHERE ID = (SELECT MAX(ID) FROM TABLE);
I am trying to update fields in my DB, but got stuck with such a simple problem: I want to update just one row in the table with the biggest id number. I would do something like that:
UPDATE table SET name='test_name' WHERE id = max(id)
Unfortunatelly it doesnt work. Any ideas?
Table Structure
id | name
---|------
1 | ghost
2 | fox
3 | ghost
I want to update only last row because ID number is the greatest one.
The use of MAX() is not possible at this position. But you can do this:
UPDATE table SET name='test_name' ORDER BY id DESC LIMIT 1;
For multiple table, as #Euthyphro question, use table.column.
The error indicates that column id is ambiguous.
Example :
UPDATE table1 as t1
LEFT JOIN table2 as t2
ON t2.id = t1.colref_t2
SET t1.name = nameref_t2
ORDER BY t1.id DESC
LIMIT 1
UPDATE table SET name='test_name' WHERE id = (SELECT max(id) FROM table)
This query will return an error as you can not do a SELECT subquery from the same table you're updating.
Try using this:
UPDATE table SET name='test_name' WHERE id = (
SELECT uid FROM (
SELECT MAX(id) FROM table AS t
) AS tmp
)
This creates a temporary table, which allows using same table for UPDATE and SELECT, but at the cost of performance.
I think iblue's method is probably your best bet; but another solution might be to set the result as a variable, then use that variable in your UPDATE statement.
SET #max = (SELECT max(`id`) FROM `table`);
UPDATE `table` SET `name` = "FOO" WHERE `id` = #max;
This could come in handy if you're expecting to be running multiple queries with the same ID, but its not really ideal to run two queries if you're only performing one update operation.
UPDATE table_NAME
SET COLUMN_NAME='COLUMN_VALUE'
ORDER BY ID
DESC LIMIT 1;
Because you can't use SELECT IN DELETE OR UPDATE CLAUSE.ORDER BY ID DESC LIMIT 1. This gives you ID's which have maximum value MAX(ID) like you tried to do. But MAX(ID) will not work.
Old Question, but for anyone coming across this you might also be able to do this:
UPDATE
`table_name` a
JOIN (SELECT MAX(`id`) AS `maxid` FROM `table_name`) b ON (b.`maxid` = a.`id`)
SET a.`name` = 'test_name';
We can update the record using max() function and maybe it will help for you.
UPDATE MainTable
SET [Date] = GETDATE()
where [ID] = (SELECT MAX([ID]) FROM MainTable)
It will work the perfect for me.
I have to update a table with consecutive numbers.
This is how i do.
UPDATE pos_facturaciondian fdu
SET fdu.idfacturacompra = '".$resultado["afectados"]."',
fdu.fechacreacion = '".$fechacreacion."'
WHERE idfacturaciondian =
(
SELECT min(idfacturaciondian) FROM
(
SELECT *
FROM pos_facturaciondian fds
WHERE fds.idfacturacompra = ''
ORDER BY fds.idfacturaciondian
) as idfacturaciondian
)
Using PHP I tend to do run a mysqli_num_rows then put the result into a variable, then do an UPDATE statement saying where ID = the newly created variable. Some people have posted there is no need to use LIMIT 1 on the end however I like to do this as it doesn't cause any trivial delay but could prevent any unforeseen actions from being taken.
If you have only just inserted the row you can use PHP's mysqli_insert_id function to return this id automatically to you without needing to run the mysqli_num_rows query.
Select the max id first, then update.
UPDATE table SET name='test_name' WHERE id = (SELECT max(id) FROM table)
I have a statement I'm using in PHP that will pull a number if it exists or, if it doesn't, it will create a row, then pull the number from the created row.
The following code works but as the title says...not the second time. First let me clarify, it works everytime if the row exists. But when a row is created and the number returned, the next time through (again with new variables) will fail but then (using same new variables again) will work correctly the next time. This is true in both php and in sql environments.
SELECT id FROM table1 WHERE authID = 'DOEJON' AND periodID = 55
IF ##ROWCOUNT = 0 INSERT INTO table1 (authID, periodID) VALUES ('DOEJON', 55);
SELECT id FROM table1 WHERE timeID = SCOPE_IDENTITY()
there appears to be some sort of refresh related to the statement - how can I get the desired results every time? thoughts?
Thank you for your kind attention.
Try Below
Declare #ID Int
SELECT #ID = id FROM table1 WHERE authID = 'DOEJON' AND periodID = 55
If (id is null)
Begin
INSERT INTO table1 (authID, periodID) VALUES ('DOEJON', 55);
Set #ID = SCOPE_IDENTITY()
End
Select #ID As 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();