Let's say I have a table like this:
name |order_id
=======================
first_record | 0
second_record | 0
third_record | 0
[...]
I want to update just order_id with an incremented value (not sure how to put this correctly in english - feel free to edit with a better description). See expected output below:
name |order_id
=======================
first_record | 1
second_record | 2
third_record | 3
[...] | n
I know how to do this either by using a script in some programming language or a sql procedure, both solution involve looping the whole table.
You can update table:
SET #oo = 0;
UPDATE table SET `order_id`=#oo:=#oo+1 ORDER By something;
Or just get order_id as returned row number while selecting:
SET #oo = 0;
SELECT name, #oo:=#oo+1 order_id FROM table ORDER By something;
Do you mean something like this? The question is not that clear.
DECLARE #order_id int
SET #order_id = 0
UPDATE #tmp_Users
SET #order_id = order_id = #order_id + 1
Related
I have a "table" named users with a column name "group_in" which stores an array like [1,2,3].
I am trying to remove an element with a value (eg. 1) for a specified row (eg id:1).
Before:
id| group_in
1 | **[1,2,3]**
2 | [1,3]
After:
id | group_in
1 | **[2,3]**
2 | [1,3]
I have tried the following:-
Update users
SET group_in = JSON_REMOVE(group_in,JSON_UNQUOTE(JSON_search(group_in, 'one', 1)))
where id = 1
but I got back is
id | group_in
1 | null
2 | [1,3]
Screenshot of my table and query result for your reference.
My table
Result gotten
Please help me if you know how to solve it
Thank you 🙏
I believe JSON_SEARCH works on strings, not sure, if it was extended to integer searches as well.
One way is to flatten the array and then recombine it while excluding the value as needed.
Query -
update users set group_in = (select new_grp from (
select id,json_arrayagg(grp) new_grp from users,
JSON_TABLE(group_in, "$[*]" COLUMNS(grp INT PATH '$')) as grp_id
where id=1
and grp<>1
group by id
)X
)
where id=1;
Refer fiddle here.
Try this,
UPDATE `channels` SET `group_in` = JSON_REMOVE(`group_in`, '$[2]') WHERE `id` = 1 ;
I have a table like this:
CREATE TABLE rows(
UniqueID VARCHAR(225),
Previous VARCHAR(225),
Next VARCHAR(225)
);
With content, that looks like this:
+----------+-----------+-----------+
| UniqueID | Previous | Next |
+----------+-----------+-----------+
| 676 | undefined | 219 |
| 890 | 219 | undefined |
| 219 | 676 | 890 |
+----------+-----------+-----------+
As you can see, the rows have UID's, which the Previous and Next columns refer to.
What I now want, is to write a SELECT * statement, that would order all the results, by the Previous and Next fields. The undefined values mark the end elements. How could I achieve that? In the case of the table showed above, the order I'd want is what's shown there, with the last 2 row positions swapped, so Next of row X Points to a UID of row Y, that has a Previous that points to the UID of the row X. etc.
What you're trying to create is a recursive query. Unfortunately, MySQL does not make this easy. There are relatively simple solutions if the parents always have an index greater than the children, but that is not the case here. There are several questions discussing this type of problem. The following question has answers that explore the different ways to attempt this type of query including using stored procedures.
How to do the Recursive SELECT query in MySQL?
Going with the stored procedure idea, you could try something like:
CREATE PROCEDURE getInOrder()
BEGIN
DECLARE child_id VARCHAR(256);
DECLARE prev_id VARCHAR(256);
SELECT UniqueID INTO prev_id FROM rows WHERE Previous = 'undefined';
SELECT `Next` INTO child_id
FROM rows WHERE UniqueID = prev_id;
CREATE TEMPORARY TABLE IF NOT EXISTS temp_table AS (SELECT * FROM rows WHERE 1=0);
TRUNCATE TABLE temp_table;
WHILE child_id <> 'undefined' DO
INSERT INTO temp_table SELECT * FROM rows WHERE UniqueID = prev_id;
SET prev_id = child_id;
SELECT `Next` INTO child_id
FROM rows WHERE UniqueID = prev_id;
END WHILE;
INSERT INTO temp_table SELECT * FROM rows WHERE UniqueID = prev_id;
SELECT * FROM temp_table;
END;
You can then call the stored procedure to retrieve the table in order.
Working example: http://sqlfiddle.com/#!9/085dec/2
ORDER BY IFNULL(prev, ''), -- some value lower than the rest
IFNULL(next, 'zzzzz') -- some value higher than all values
(Technically, the first part could be simply prev, without the IFNULL.)
If the ids are really numbers, you should use a numeric datatype such as INT UNSIGNED. If they are really strings, do you need 225?
This assumes that prev < next -- Is that necessarily the case? It seems like arbitrary links might not maintain that. If you need to look at next to load the next row based on UniqueId, the code is much more complex.
I think this request lacks on details.
But, you want the final result to be like this?
+----------+-----------+-----------+
| UniqueID | Previous | Next |
+----------+-----------+-----------+
| 676 | undefined | 219 |
| 219 | 676 | 890 |
| 890 | 219 | undefined |
+----------+-----------+-----------+
If I'm right, you can achieve it with (I named the table as demo):
SELECT d.* FROM (
SELECT UniqueID, IF(Previous IS NULL, -1, Previous) AS Previous, IF(Next IS NULL, 999999999999, Next) as Next
FROM demo
)t
JOIN demo d ON d.UniqueID = t.UniqueID
ORDER BY t.Next, t.Previous
;
So, when Previous is NULL you put it with -1 to ensure he's is the first on the list and when Next is NULL you put it with a very high value to ensure it will be the last on the list... then you just have to order the query by Previous and Next.
I must stress that this solution is focused on presented data.
I have this wrong query:
update product prod set
prod.id = (select fur.p_id
from furnisher fur
where prod.row number = fur.row number
)
What I wanna do is to set the p_id from the first row of the table furnisher to the id of the first row of the table product.
the same for the other elements...
I didn't find the exact syntax to execute my query (my dbms is mySql)
For example I have:
product |id|name |....
|1 |prod1|
|2 |prod2|
....
fournitsher p_id|activation_date|status|...
500 |'01-01-205' | true |
1000|'01-01-205' | true |
....
my table product should contain now :
product |id |name |....
|500 |prod1|
|1000 |prod2|
Since you only want to do it for the first row, you can achieve this with limit. Note that since you want a first row, it should be given an order, else it is illogical as we don't really know what "first" mean. So order it by whatever you want
update furnisher a
join (select p_id
from furnisher
order by any_field
limit 1) b using(p_id)
set a.p_id = (select id
from product prod
order by any_field
limit 1);
I tried this solution and it solves my problem :)
CREATE PROCEDURE ROWPERROW()
BEGIN
DECLARE n INT DEFAULT 0;
DECLARE i INT DEFAULT 0;
SELECT COUNT(*) FROM product INTO n;
SET i=0;
WHILE i<n DO
update product set id = ( select p_id from furnisher LIMIT i,1);
SET i = i + 1;
END WHILE;
End;
;;
then I call my procedure
call ROWPERROW();
If I have table structure as so:
CREATE TABLE a (
aid INT AUTO_INCREMENT,
acol1 INT,
acol2 INT,
PRIMARY KEY(aid);
)
CREATE TABLE b (
bid INT AUTO_INCREMENT,
bcol INT,
PRIMARY KEY(bid);
)
and run the statement:
`INSERT INTO a SET acol1 = (SELECT MAX(acol1) + 1 as newMax FROM a WHERE id = ?)
Is there anyway for me to retrieve the value of newMax after the query is executed? I am looking for something similar to last_insert_id() in PHP but for temporary values in the query.
Obviously I am trying to not query the database again if possible.
EDIT:
Actual situation:
CREATE TABLE group (
group_id INT AUTO_INCREMENT,
PRIMARY KEY(group_id)
) ENGINE = MyISAM;
CREATE TABLE item (
group_refid INT, --references group.group_id
group_pos INT, --represents this item's position in its group
text VARCHAR(4096), --data
PRIMARY KEY(group_refid, group_pos)
) ENGINE = MyISAM;
So the issue is that when I add a new item to a group, I need to make its
group_pos = MAX(group_pos) WHERE group_refid = ?
which would require a query with something like:
INSERT INTO item (group_refid, group_pos) SET group_refid = 1, group_pos = (SELECT MAX(group_pos) + 1 FROM item WHERE group_refid = 1);
As you know, this query does not work. There is added complexity that there may not be an item entry yet for a particular group_id.
I am trying to get this all into one atomic statement to prevent race conditions.
INSERT INTO item (group_refid,group_pos)
SELECT 1, (
SELECT IFNULL(MAX(group_pos),0) + 1
FROM item
WHERE group_refid=1
);
However, if we're talking MyISAM tables explicitly, not another engine, this would work:
mysql> CREATE TABLE items (group_refid INT, group_pos INT AUTO_INCREMENT, PRIMARY KEY(group_refid,group_pos)) ENGINE=MyISAM;
Query OK, 0 rows affected (0.12 sec)
mysql> INSERT INTO items (group_refid) VALUES (1),(2),(1),(1),(2),(4),(2),(1);
Query OK, 8 rows affected (0.02 sec)
Records: 8 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM items ORDER BY group_refid, group_pos;
+-------------+-----------+
| group_refid | group_pos |
+-------------+-----------+
| 1 | 1 |
| 1 | 2 |
| 1 | 3 |
| 1 | 4 |
| 2 | 1 |
| 2 | 2 |
| 2 | 3 |
| 4 | 1 |
+-------------+-----------+
However, that AUTO_INCREMENT on a second column in the PK is not portable to another database engine.
you cant. insert query is for insering not selecting.
You must run other query like that
SELECT MAX(acol1) + 1 as newMax FROM a WHERE acol2 = ?
for more read this
I think you can do:
INSERT INTO b
SET bcol = (SELECT #acol := MAX(acol1) + 1 as newMax FROM a WHERE acol2 = ?);
Then you can use the variable #acol to get the value you want.
EDIT:
Is this what you want?
INSERT INTO item (group_refid, group_pos)
SELECT 1, MAX(group_pos) + 1
FROM item
WHERE group_refid = 1;
Not directly in the statement, no. You'll need a separate statement to retrieve values.
But, you could "capture" the value from the SELECT into a user-defined variable, and then retrieve that with a SELECT (in the same database session), if you needed to "know" the value returned from the SELECT.
For example:
INSERT INTO b (bcol)
SELECT #bcol := (MAX(a.acol1) + 1) AS newMax
FROM a WHERE a.acol2 = ?)
SELECT #bcol + 0 AS new_bcol
NOTE:
Note that the user-defined variable assigned in the select is subject to modification elsewhere in the session, for example, it could be overwritten by the execution of a trigger defined the target table of the INSERT.
As an edge case, not that anyone would do this, but it's also possible there might be a BEFORE INSERT trigger that modifies the value of bcol, before it gets inserted. So, if you need to "know" the value that was actually inserted, that would be available in an AFTER INSERT trigger. You could capture that in a user-defined variable in that trigger.
Running a second, separate query against the a table is subject to a race condition, a small window of opportunity for a another session to insert/update/delete a row in table a, such that it's possible that a second query could return a different value than the first query... it might not be the value that was retrieved the first time. Unless of course you are within the context of an InnoDB transaction with REPEATABLE READ isolation level, or you've implemented some concurrency-killing locking strategy.
I need to update rows by their number(not AI ID, cause some of the rows may will be removed). How can I do this?
I mean something like this:
UPDATE cars SET idx = value WHERE row_number = i
I would do this in a 'for' statement, and i is the integer of my statement. So I would update every row in the statement.
Sorry for my bad english, and thanks!
Here's a pure MySQL solution:
/*test data*/
create table foo (id int auto_increment primary key, a int);
insert into foo (a) values (10), (11), (12);
/*update statement*/
update foo
set a = 5
where id = (
select id from (
select id, #rownum:=#rownum + 1 as rownumber
from foo, (select #rownum:=0) vars order by id
) sq where rownumber = 2
);
Results in:
| ID | A |
-----|----|--
| 1 | 10 |
| 2 | 5 |
| 3 | 12 |
Feel free to ask if you have any questions about this.
Also, note the order by id in there. It's important, cause in a database there is no first or last row. Without an order by clause theoretically there could be each time a different result.
You can also see it working live here in an sqlfiddle.
i don't know this about mysql but you can do this in php
$row_number=? ;//the row no of mysql you want to change the id
$id=? ;//the new id
mysql_connect //do it yourself
$query="select 8 from tablename"; //the query
$result=mysql_query($qyery,$conn);
$count=0;
while($row=mysql_fetch_array($result)) // fetch each row one by one an put data in array $row
{
$count++; //increment count means the no of rows are incermented
if($count==$rownumber) //the row where you want to edit the id
{
$query1="update tablename set id='".$id."' where id=".$row["id"]; //new query on that particular row
$result1=mysql_query($query1,$conn);
}
}
this will work , just modify this code according to your use