say I have a simple tree type table
id(key) | parent | order
============================
1 | 0 | 0
2 | 0 | 1
4 | 2 | 0
5 | 2 | 1
6 | 2 | 2
I want to insert a new node so that it has parent = 2 and order = 1, so it then the table data looks like:
id(key) | parent | order
============================
1 | 0 | 0
2 | 0 | 1
4 | 2 | 0
5 | 2 | 2
6 | 2 | 3
7 | 2 | 1
E.g. existing rows increment their order value.
What's the best way to ensure that existing rows increment their order (non-key field) starting at an existing arbitrary value, to make a hole for my insert statement?
If you have a new row with parent $p and order position $o you can:
UPDATE table SET order = order + 1 WHERE parent = $p AND order >= $o
and then:
INSERT INTO order (id,parent,order) VALUES($id,$p,$o)
Related
I have a MySQL table storing a binary tree in a nested set model with some extra properties. The binary tree is neither full nor complete, so there may be nodes on the middle with only one child.
It looks something like this (but with much more data):
+----+------+-------+-----------+-------+----------+--------------------+
| id | left | right | parent_id | level | position | number_of_children |
+----+------+-------+-----------+-------+----------+--------------------+
| 1 | 1 | 8 | NULL | 1 | LEFT | 3 |
| 2 | 2 | 3 | 1 | 2 | LEFT | 0 |
| 3 | 4 | 7 | 1 | 2 | RIGHT | 1 |
| 4 | 5 | 6 | 2 | 3 | LEFT | 0 |
+----+------+-------+-----------+-------+----------+--------------------+
How could I query the leftmost or the rightmost node of a tree or sub-tree?
Some graphic explanation: https://imgur.com/w7gxtOC
I tried it multiple ways, but these are not working on all scenarios (these are examples for the leftmost):
SELECT * FROM nodes
WHERE position = 'LEFT'
AND number_of_children < 2
HAVING `right` = `left` + 1
ORDER BY element.`left` ASC
LIMIT 1;
Or this one, it definitely finds the solution but finds some false ones too:
SELECT * FROM nodes AS element
JOIN nodes AS upline ON element.parent_id = upline.id
WHERE upline.position = 'LEFT'
AND element.position = 'LEFT'
AND element.number_of_children < 2
ORDER BY element.`left` ASC;
I have a table of food items. They have a "Position" field that represents the order they should appear in on a list (listID is the list they are on, we don't want to re-order items on another list).
+--id--+--listID--+---name---+--position--+
| 1 | 1 | cheese | 0 |
| 2 | 1 | chips | 1 |
| 3 | 1 | bacon | 2 |
| 4 | 1 | apples | 3 |
| 5 | 1 | pears | 4 |
| 6 | 1 | pie | 5 |
| 7 | 2 | carrots | 0 |
| 8,9+ | 3,4+ | ... | ... |
+------+----------+----------+------------+
I want to be able to say "Move Pears to before Chips" which involves setting the position of Pears to position 1, and then incrementing all the positions inbetween by 1. so that my resulting Table look like this...
+--id--+--listID--+---name---+--position--+
| 1 | 1 | cheese | 0 |
| 2 | 1 | chips | 2 |
| 3 | 1 | bacon | 3 |
| 4 | 1 | apples | 4 |
| 5 | 1 | pears | 1 |
| 6 | 1 | pie | 5 |
| 7 | 2 | carrots | 0 |
| 8,9+ | 3,4+ | ... | ... |
+------+----------+----------+------------+
So that all I need to do is SELECT name FROM mytable WHERE listID = 1 ORDER BY position and I'll get all my food in the right order.
Is it possible to do this with a single query? Keep in mind that a record might be moving up or down in the list, and that the table contains records for multiple lists, so we need to isolate the listID.
My knowledge of SQL is pretty limited so right now the only way I know of to do this is to SELECT id, position FROM mytable WHERE listID = 1 AND position BETWEEN 1 AND 5 then I can use Javascript (node.js) to change position 5 to 1, and increment all others +1. Then UPDATE all the records I just changed.
It's just that anytime I try to read up on SQL stuff everyone keeps saying to avoid multiple queries and avoid doing syncronous coding and stuff like that.
Thanks
This calls for a complex query that updates many records. But a small change to your data can change things so that it can be achieved with a simple query that modifies just one record.
UPDATE my_table set position = position*10;
In the old days, the BASIC programming language on many systems had line numbers, it encouraged spagetti code. Instead of functions many people wrote GOTO line_number. Real trouble arose if you numbered the lines sequentially and had to add or delete a few lines. How did people get around it? By increment lines by 10! That's what we are doing here.
So you want pears to be the second item?
UPDATE my_table set position = 15 WHERE listId=1 AND name = 'Pears'
Worried that eventually gaps between the items will disappear after multiple reordering? No fear just do
UPDATE my_table set position = position*10;
From time to time.
I do not think this can be conveniently done in less than two queries, which is OK, there should be as few queries as possible, but not at any cost. The two queries would be like (based on what you write yourself)
UPDATE mytable SET position = 1 WHERE listID = 1 AND name = 'pears';
UPDATE mytable SET position = position + 1 WHERE listID = 1 AND position BETWEEN 2 AND 4;
I've mostly figured out my problem. So I've decided to put an answer here incase anyone finds it helpful.
I can make use of a CASE statement in SQL. Also by using Javascript beforehand to build my SQL query I can change multiple records.
This builds my SQL query:
var sql;
var incrementDirection = (startPos > endPos)? 1 : -1;
sql = "UPDATE mytable SET position = CASE WHEN position = "+startPos+" THEN "+endPos;
for(var i=endPos; i!=startPos; i+=incrementDirection){
sql += " WHEN position = "+i+" THEN "+(i+incrementDirection);
}
sql += " ELSE position END WHERE listID = "+listID;
If I want to move Pears to before Chips. I can set:
startPos = 4;
endPos = 1;
listID = 1;
My code will produce an SQL statement that looks like:
UPDATE mytable
SET position = CASE
WHEN position = 4 THEN 1
WHEN position = 1 THEN 2
WHEN position = 2 THEN 3
WHEN position = 3 THEN 4
ELSE position
END
WHERE listID = 1
I run that code and my final table will look like:
+--id--+--listID--+---name---+--position--+
| 1 | 1 | cheese | 0 |
| 2 | 1 | chips | 2 |
| 3 | 1 | bacon | 3 |
| 4 | 1 | apples | 4 |
| 5 | 1 | pears | 1 |
| 6 | 1 | pie | 5 |
| 7 | 2 | carrots | 0 |
| 8,9+ | 3,4+ | ... | ... |
+------+----------+----------+------------+
After that, all I have to do is run SELECT name FROM mytable WHERE listID = 1 ORDER BY position and the output will be as follows::
cheese
pears
chips
bacon
apples
pie
I've got this MySQL-table:
id | staffId | companyId | active | somevalue
When I create an UNIQUE index on staffId, companyId and active I can store a maximum of two records. One with active 1 and one with active 0.
I would like to make sure I can have only one active record while it is possible to have multiple inactive records. For example:
1 | 1 | 1 | 1 | 1
1 | 1 | 1 | 0 | 5
1 | 1 | 1 | 0 | 7
Should be possible, but adding this record should cause an error:
1 | 1 | 1 | 1 | 9
Choosing NULL instead of 0 for an incactive record seems to work :-) I wonder if there are better solutions?
I have a statement that tries to insert a record and if it already exists, it simply updates the record.
INSERT INTO temptable (col1,col2,col3)
VALUES (1,2,3)
ON DUPLICATE KEY UPDATE col1=VALUES(col1), col2=VALUES(col2), col3=VALUES(col3);
The full statement has multiple inserts and I'm looking to count number of INSERTs against the UPDATEs. Can I do this with MySQL variables, I've yet to find a way to do this after searching.
From Mysql Docs
In the case of "INSERT ... ON DUPLICATE KEY UPDATE" queries, the return value will be 1 if an insert was performed, or 2 for an update of an existing row.
Use mysql_affected_rows() after your query, if INSERT was performed it will give you 1 and if UPDATE was performed it will give you 2.
I've accomplished what you're describing using a while loop so that each iteration creates a MySQL statement that affects one row. Within the loop, I run the mysql_affected_rows() and then increment a counter depending upon whether the value returned was a 0 or a 1. At the end of the loop, I echo both variables for viewing.
The complete wording from MySQL Docs regarding the mysql_affected_rows function is (notice there are 3 possible values returned - 0, 1, or 2):
For INSERT ... ON DUPLICATE KEY UPDATE statements, the affected-rows
value per row is 1 if the row is inserted as a new row, 2 if an
existing row is updated, and 0 if an existing row is set to its
current values. If you specify the CLIENT_FOUND_ROWS flag, the
affected-rows value is 1 (not 0) if an existing row is set to its
current values.
(Sidenote - I set $countUpdate and $countInsert and $countUpdateNoChange to 0 prior to the while loop):
Here's the code that I developed that works great for me:
while (conditions...) {
$sql = "INSERT INTO test_table (control_number, name) VALUES ('123', 'Bob')
ON DUPLICATE KEY UPDATE name = 'Bob'";
mysql_query($sql) OR die('Error: '. mysql_error());
$recordModType = mysql_affected_rows();
if ($recordModType == 0) {
$countUpdateNoChange++;
}elseif($recordModType == 1){
$countInsert++;
}elseif($recordModType == 2){
$countUpdate++;
};
};
echo $countInsert." rows inserted<br>";
echo $countUpdateNoChange." rows updated but no data affected<br>";
echo $countUpdate." rows updated with new data<br><br>";
Hopefully, I haven't made any typos as I've recreated it to share while removing my confidential data.
Hope this helps someone. Good luck coding!
I know this is a bit old, but I was doing a bulk insert in PHP and needed to know exactly how many rows were inserted and updated (separately).
So I used this:
$dataCount = count($arrData); // number of rows in the statement
$affected = mysql_affected_rows(); // mysqli_*, PDO's rowCount() or anything
$updated = $affected - $dataCount;
$inserted = 2 * $dataCount - $affected;
Simple trace table:
-------------------------------
| data | affected | ins | upd |
-------------------------------
| 1 | 1 | 1 | 0 |
-------------------------------
| 2 | 2 | 2 | 0 |
| 2 | 3 | 1 | 1 |
| 2 | 4 | 0 | 2 |
-------------------------------
| 3 | 3 | 3 | 0 |
| 3 | 4 | 2 | 1 |
| 3 | 5 | 1 | 2 |
| 3 | 6 | 0 | 3 |
-------------------------------
| 4 | 4 | 4 | 0 |
| 4 | 5 | 3 | 1 |
| 4 | 6 | 2 | 2 |
| 4 | 7 | 1 | 3 |
| 4 | 8 | 0 | 4 |
-------------------------------
| 5 | 5 | 5 | 0 |
| 5 | 6 | 4 | 1 |
| 5 | 7 | 3 | 2 |
| 5 | 8 | 2 | 3 |
| 5 | 9 | 1 | 4 |
| 5 | 10 | 0 | 5 |
-------------------------------
if you want to get the number of records that have been inserted and updated separetly, you are to issue each statement separetly.
If I have the following table & data to allow us to use the sort_index for sorting:
CREATE TABLE `foo` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`bar_id` INT(11) DEFAULT NULL,
`sort_index` INT(11) DEFAULT NULL,
PRIMARY KEY (`id`)
);
INSERT INTO `foo` (`bar_id`, `sort_index`) VALUES
(1,1),(1,2),(1,3),(1,4),
(2,1),(2,2),(2,3),(2,4),(2,5);
I want to be able to do the following in the most efficient manner:
Move a foo entry to a given position (scoped by the bar_id)
Ensure that the sort_index is always 1 indexed and has no gaps
You should be able to move items to the beginning and end of the list and rule #2 should still be applied
It should be done entirely in queries and as few as possible (as the sets could be very large and looping over them doing individual UPDATEs is not ideal)
To clarify what I'm trying to do, lets assume the table was empty so we have the following data:
id | bar_id | sort_index
1 | 1 | 1
2 | 1 | 2
3 | 1 | 3
4 | 1 | 4
5 | 2 | 1
6 | 2 | 2
7 | 2 | 3
8 | 2 | 4
9 | 2 | 5
Then if we were to do the following moves
Foo 1 to sort_index 3
Foo 7 to sort_index 1
Foo 5 to sort_index 5
We should get the following data:
id | bar_id | sort_index
1 | 1 | 3
2 | 1 | 1
3 | 1 | 2
4 | 1 | 4
5 | 2 | 5
6 | 2 | 2
7 | 2 | 1
8 | 2 | 3
9 | 2 | 4
And SELECT * FROM foo ORDER BY bar_id, sort_index; gives us:
id | bar_id | sort_index
2 | 1 | 1
3 | 1 | 2
1 | 1 | 3
4 | 1 | 4
7 | 2 | 1
6 | 2 | 2
8 | 2 | 3
9 | 2 | 4
5 | 2 | 5
You should be able to do this in a single query: something along the lines of UPDATE foo SET sort_index = sort_index + 1 WHERE bar_id == b AND sort_index < s1 AND sort_index >= s2, where b is the bar_id of the row to be moved, s1 is the current sort_index of that row, and s2 is the the sort_index you want to move it to. Then, you'd just change the sort_index of the row.
You'd probably want to do the two queries inside a transaction. Also, it might speed things up if you created an index on the sort_index using something like CREATE INDEX foo_index ON foo (sort_index).
(By the way, here I'm assuming that you don't want duplicate sort_index values within a given bar_id, and that the relative order of rows should never be changed except explicitly. If you don't need this, the solution is even simpler.)