I have created a table A having a id (serial) field.
I have created a seeding sql file, where I specify explicitly the id values, because I have also to populate related tables having foreign key that refers to this id field.
All the seeding sql script run fine.
But when it comes to perform a new insert in my table A (without specifying the id, serial, because I want it to be auto incremented) I get back a duplicate key error. Looks like that after the first seeding script. Postgres doesn't auto increment the index.
In fact, if I had inserted, let's say 3 records in the seeding phase, I'll get back three times the error from the subsequent inserts with id NULL, and then it starts inserting everything as expected. I.e. even if it report duplicate key error, it's incrementing the auto increment value each query sent.
How do you usually manage this?
Thanks
You are facing this problem because "current value of your table sequence id is different". you can change it in your database.
If you are using pgadmin then go to your schema > sequences > yourtablename_id_seq > change current value.
Related
I was just creating a new table using MySQL Query Browser, and noticed there's a tick under Auto Increment Column. How does that work?
When adding to the database programatically, do I just add a number, and then the database automatically increments that number?
Everytime a NEW user registers on my site, I want their Customer ID (integer only) to auto increment, so I don't have to try and randomly generate a unique number.
Can this be done simply?
Thank you!
When adding to the database programatically, do I just add a number, and then the database automatically increments that number?
Yes, that's the way auto_increment works.
The value will be incremented for each new row
The value is unique, duplicates are not possible
If a row is deleted, the auto_increment column of that row will not be re-assigned.
The auto_increment value of the last inserted row can be accessed using the mySQL function LAST_INSERT_ID() but it must be called right after the insert query, in the same database connection
mySQL Reference
1 more,
You can insert your own value also (ie your random value).
Yes. Auto_Increment columns work like they say on the tin. Tips
when INSERT - ing, use NULL or omit the column
Use LAST_INSERT_ID() (or API equivalents) to obtain the last generated value.
for security and business logic reasons, it's usually better form to not directly use a key value for a customer identifier. Consider using Hashed / randomised surrogate customer keys instead.
Ta
Yes, that's the exact purpose of AUTO_INCREMENT. It looks at whatever is the current increment value for that table, and stores that value plus 1 for the new row that comes in, automatically. You can omit that field from your INSERT statements and MySQL will handle it for you for every new row that comes in, giving each row its own unique ID.
When you enable Auto Increment an ID will always get automatically added whenever a new record is made.. Example:
If you have 1 record with ID 1 in your table and you add a new record, the ID will automatically be 2.
I am currently starting web development and am now working on a very simple script that posts entry data from a from to a mysql database. But the problem I have been encountering is that when I submit the form I get the following error:
Error: Duplicate entry '0' for key 'PRIMARY'
To me it seems a really weird error as the table is completely empty, ID is set to auto_increment and I am not trying to assign any value to it.
I am using Xampp for my localhost on Mac OS btw.
This is my form (.php):
This is my mysql entry script (.php):
The result is this:
This is the database setup:
The weird thing is that when the table is empty, and I insert through the form the first time, something does end up in the database. But it is missing "email" and "password" and shows "NULL". The second time I use the form, nothing is added in the database:
Your id column does not seem to be auto-incrementing. It is not generating a new id for every row. It just defaults to 0 if you don't supply a value for it.
Nonetheless there's a UNIQUE/PRIMARY constraint on that column, so the id 0 cannot occur more than once. Since you're not supplying an id and MySQL isn't generating one (because the column isn't auto-incrementing), you cannot insert more than one row.
You're issuing three separate INSERT INTO statements which will result in three separate rows to be inserted (if you could insert more than one row, see above), each with a different value set; but never one row with all values set.
So:
Make your id column actually auto-incrementing.
Prepare a single INSERT INTO statement which inserts all values in one go:
INSERT INTO members (name, email, password) VALUES (.., .., ..)
See Why shouldn't I use mysql_* functions in PHP? and stop using mysql_*. Learn about prepared statements, read The Great Escapism (Or: What You Need To Know To Work With Text Within Text) for why.
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.
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?