In my MySQl table I have two fields, id and order. id is an auto-incrementing primary key and I want order's initial value to match this, but to also be editable, not a key and with no uniqueness constraints. How can my database insert method achieve this? Is it possible to do so without requerying to find the last inserted id?
I'm using paris/idiorm so a solution making use of their features would be handy, although plain SQL and php is fine too.
In MySQL (since version 5.0.2) you can create trigger.
Try this on non-production database:
create trigger default_order_value AFTER INSERT ON orders
UPDATE order SET order = id WHERE id = new.id;
It may not work in that way as you wish, but you can edit it. This is another trigger example:
CREATE TRIGGER default_order
BEFORE UPDATE ON orders
REFERENCING NEW ROW AS n
n.order = n.id;
Related
Just looking for some tips and pointers for a small project I am doing. I have some ideas but I am not sure if they are the best practice. I am using mysql and php.
I have a table called nomsing in the database.
It has a primary key called row id which is an integer.
Then I have about 8 other tables referencing this table.
That are called nomplu, accsing,accplu, datsing, datplu for instance.
Each has a column that references the primary key of nomsing.
Withing my php code I have all the information to insert into the tables except one thing , the row id primary key of the nomsing table. So that php generates a series of inserts like the following.
INSERT INTO nomsing(word,postress,gender) VALUES (''велосипед","8","mask").
INSERT INTO nomplu(word,postress,NOMSING?REFERENCE) VALUES (''велосипеды","2",#the reference to the id of the first insert#).
There are more inserts but this one gets the point across. The second insert should reference the auto generated id for the first insert. I was this to work as a transaction so all inserts should complete or none.
One idea I have is to not auto generate the id and generate it myself in php. That way would know the id given before the transaction but then I would have to check if the id was already in the db.
Another idea I have is to do the first insert and then query for the row id of that insert in php and then make the second insert. I mean both should work but they don't seem like an optimal solution. I am not too familiar with the database transactional features but what would be the best approach to do in this case. I don't like the idea of inserting then querying for the id and then running the rest of the queries. Just seems very inefficient or perhaps I am wrong.
Just insert a row in the master table. Then you can fetch the insert id ( lastInserId when on PDO) and use that to populate your other queries.
You could use the php version as given by JvdBerg , or Mysql's LAST_INSERT_ID. I usually use the former option.
See a similar SO question here.
You could add a new column to the nomsing table, called 'insert_order' (or similar) with a default value of 0, then instead of generating one SQL statement per insert create a bulk insert statement e.g.
INSERT INTO nomsing(word,postress,gender, insert_order)
VALUES (''велосипед","8","mask",1), (''abcd'',"9","hat",2).....
you generate the insert_order number with a counter in your loop starting at one. Then you can perform one SELECT on the table to get the ids e.g.
SELECT row_id
FROM nomsing
WHERE insert_order > 0;
now you have all the IDs you can now do a bulk insert for your following queries. At the end of your script just do an update to reset the insert_order column back to 0
UPDATE nomsing SET insert_order = 0 WHERE insert_order > 0;
It may seem messy to add an extra column to do this but it will add a significant speed increase over performing one query at a time.
I would like write a php script that merges several databases, and I would like to be sure of how to go around it before I start anything.
I have 4 databases which have the same structure and almost same data. I want to merge them without any duplicate entry while preserving (or re-linking) the foreign keys.
For example there is a db1.product table which is almost the same as db2.products so I think I would have to use LIKE comparison on name and description columns to be sure that I only insert new rows. But then, when merging the orders table I have to make sure that the productID still indicates the right product.
So I thought of 2 solutions :
Either I use for each table insert into db1.x as select * from db2.x and then make new links and check for duplicate using triggers.
Either I delete duplicate entries and update new foreign keys (after having dropped constraints) and then insert row into the main database.
Just heard of MySQL Data Compare and Toad for mySQL, could they help me to merge tables ?
Could someone indicate to me what should be the right solution ?
sorry for my english and thank you !
First thing is how are you determining whether products are the same? You mentioned LIKE comparison on name and description. You need to establish a rule what says that product is one and the same in your db1, db2 and so on.
However, let's assume that product's name and description are the attributes that define it.
ALTER TABLE products ADD UNIQUE('name', 'description');
Run this on all of your databases.
After you've done that, select one of the databases you wish to import into and run the following query:
INSERT IGNORE INTO db1.products SELECT * FROM db2.products;
Repeat for the remaining databases.
Naturally, this all fails if you can't determine how you're going to compare the products.
Note: never use reserved words for your column names such as word "name".
Firstly, good luck with this - sounds like a tricky job.
Secondly, I wouldn't do this with PHP - I'd write SQL to do the work, assuming this is a one-off migration task and not a recurring task.
As an approach, I would do the following.
Create a database with the schema you want - it sounds like each of your 4 databases have small variations in the schema. Just create the schema for now, don't worry about the data.
Create a "working" database, with the same schema, but with columns for "old" primary keys. For instance:
table ORDER
order_id int primary key auto increment
old_order_id int not null
...other columns...
table ORDER_LINE
order_line_id int primary key auto increment
old_order_line_id int not null
order_id int foreign key
...other columns...
Table by table, Insert into your working database from your first source database. Let the primary keys auto_increment, but put the original primary key into the "old_" column.
For instance:
insert into workingdb.orders
select null, order_id, ....other columns...
from db1.orders
Where you have a foreign key, populate it by finding the record in the old_ column.
For instance:
insert into workingdb.order_line
select null, ol.order_line_id, o.order_id
from db1.order_line ol,
workingdb.order
where ol.order_id = o.old_order_id
Rinse and repeat for the other databases.
Finally, copy the data from your working database into the "proper" database. This is optional - it may help to retain the old IDs for lookups etc.
My db table looks like this pic. http://prntscr.com/22z1n
Recently I've created delete.php page. it works properly but when i deleted 21th user next registered user gets 24th id instead of 21.
Is it possible to put newly registered users info to first empty row? (In this situation 21th row)
In my registration form, newly registering user can write names of existing users, and be friends with them after registration. For this friendship i have another table that associates id of newly registered user and existing user.
For this purpose i'm using mysql_insert_id during registration to get id for new user. But after deletion of 21th row during nex registration process mysql_insert_id gave me number 21. but stored in 24th row. And put to associations table 21 for new user. I wanna solve this problem
When you use an autoincrement id column, the value that the next entry will be assigned will not be reduced by deleting an entry. That is not what an autoincrement column is used for. The database engine will always increment that number on a new insert and never decrement that number on a delete.
A MySQL auto_increment column maintains a number internally, and will always increment it, even after deletions. If you need to fill in an empty space, you have to handle it yourself in PHP, rather than use the auto_increment keyword in the table definition.
Rolling back to fill in empty row ids can cause all sorts of difficulty if you have foreign key relationships to maintain, and it really isn't advised.
The auto_increment can be reset using a SQL statement, but this is not advised because it will cause duplicate key errors.
-- Doing this will cause problems!
ALTER table AUTO_INCREMENT=12345;
EDIT
To enforce your foreign key relationships as described in the comments, you should add to your table definition:
FOREIGN KEY (friendid) REFERENCES registration_table (id) ON DELETE SET NULL;
Fill in the correct table and column names. Now, when a user is deleted from the registration, their friend association is nulled. If you need to reassociate with a different user, that has to be handled with PHP. mysql_insert_id() is no longer helpful.
If you need to find the highest numbered id still in the database after deletion to associate with friends, use the following.
SELECT MAX(id) FROM registration_table;
Auto increment is a sequence key that's tracked as part of the table. It does not go back when you delete a row.
Easily, no. What you can do (but I don't suggest doing) is making an SQL function to determine the lowest number that isn't currently occupied. Or you can create a table of IDs that were deleted, and get the smallest number from there. Or, and this is the best idea, ignore the gaps and realize the database is fine.
What you want to do is achievable by adding an extra column to your table called something like user_order. You can then write code to manage inserts and deletions so that this column is always sequential with no gaps.
This way you avoid the problems you could have messing around with an auto_increment column.
It's not a good practice to reset auto_increment value, but if you really need to do it, so you can:
ALTER TABLE mytable AUTO_INCREMENT = 1;
Run this query after every delete. Auto_increment value will not be set to 1, this will set the lowest possible value automatically.
I have created a PHP script and I am lacking to extract the primary key, I have given flow below, please help me in how can i modify to get primary key
I am using MySQL DB, working for Joomla, My requirement is tracking the activity like insert/update/delete on any table and store it in another audit table using triggers, i.e. I am doing Auditing. DB's table structure: Few tables dont have any PK nor auto increment key
Flow of my script is :
I fetch out all table from DB.
I check whether the table have any trigger or not.
If yes then it moves to check for next table and so on.
If it does'nt find any trigger then it creates the triggers for the table, such that,
it first checks if the table has any primary key or not(for inserting in Tracking audit table for every change made)
if it has the primary key then it uses it further in creation of trigger.
if it doesnt find any PK then it proceeds further in creating the trigger without inserting any id in audit table
Now here, My problem is I need the PK every time so that I can record the id of any particular table in which the insert/update/delete is performed, so that further i can use this audit track table to replicate in production DB..
Now as I haave mentioned earlier that I am not available with PK/auto-incremented in some table, then what should I do get the particular id in which change is done?
please guide me...GEEKS!!!
If I understand your question right, you need a unique identifier for table rows that have no primary key and no other kind of unique identifier. That's not easy to do as far as I can see. Other databases have unique Row IDs, but mySQL does not. You could use the value of every column to try and identify the row, but that is far from duplicate-safe - there could be two or more rows containing the exact same values. So I'd say, without a unique identifier, this is something that simply cannot be done.
Some ideas in this SO question:
MySQL: is there something like an internal record identifier for every record in a MySQL table?
I had a hard time with the title, so let me explain.
What I'm doing is using the jQuery UI to create sortable list elements on a page. Once the order is submitted, php assigns an incrementing value to the list elements based on their order, drops the existing id column, creates a new id column and inserts each list elements value WHERE title=x. This creates the proper order of ID's, and is working fine.
What I'd like to do now is change the column to auto_increment, such that if I insert a new entry, the id is assigned automatically, one number higher than the greatest number generated by the php script. I'm not using any foreign keys or anything, just this simple table.
Is this possible?
My mistake, I misread your question. You do not want to use the database itself to provide numbering based on your sort order. You can however use the SQL query itself to return an incrementing field. One sec and I'll update with that info...
Ok, here it is:
you need to use a variable like
set #n=0;SELECT
#n:=#n+1 as 'n',
col1,
col2
from table
However, i highly recommend you just create the numbering in your php code if at all possible.
----------------Original Post----------------
This is pretty easy with phpmyadmin. Let me know if your unable to install that and I'll dig up the necessary SQL.
All heck, here is the SQL:
alter table t1 modify f1 int(4) auto_increment
alter TABLE tbl auto_increment = xxx; //change xxx to be the next id it should use
you may need to run these in opposite order depending on your existing data set it will fail to add auto_increment if you don't change the value of auto_increment to be something not already in use.