I am working on a database application with MySQL and PHP. At this moment I'm trying to get the changes caused by the last UPDATE. My first way to solve the problem is
getting the 'old' state with SELECT
Doing the changes with UPDATE
getting the 'new' state with SELECT
comparing the arrays with php
These are three mysql-connections...
Is there any way to shorten this?
You could do an before update trigger that will push an entire copy of the record to a history table that also contains additional state data you wish to store (updated date, user etc.)
This way you will have a complete revision history of what happened with what records and it should happen transparently. only think to remember is you should drop any unique constraints from the history table.
Hope this helps.
you can use the following hack using variables:
update table set
col=(#oldValue:=col),col=newValue
where id=1234;
select #oldValue;
Let me tell you how I do that,
When I update a row, firstly I get which row I'm updating and I call them active records. Then I compare each column of active records with the form fields. That's how I know which column has changed.
And if you want to store changed columns, create history table that would be like;
id (for primary key)
tablename (which table i'm updating)
recordid (which row i'm updating)
column (which columns has been changed)
oldvalue (active record value)
newvalue (form value-updated value)
date (obvious)
user (who did this change)
After that, you can use your imagination for structures how you want to use.
Related
I am implementing a request mechanism where the user have to approve a request. For that i have implemented a temporary table and main table. Initially when the request is added the data will be inserted to the temporary table, on approval it will be copied to the main table.
The issue is there will be more than 5k rows to be moved to the main table after approval + another 3-5 row for each row in the detail table (stores the details).
My current implementation is like this
//Get the rows from temporary table (batch_temp)
//Loop through the data
//Insert the data to the main table (batch_main) and return the id
//Get the details row from the temporary detail table (batch_temp_detail) using detail_tempid
//Loop through the data
//Insert the details to the detail table (batch_main_detail) with the main table id amount_id
//End Loop
//End Loop
But this implementation would take atleast 20k queries. Is there any better ways to implement the same.
I tried to create a sqlfiddle but was unable to create one. So i have pasted the query in pgsql.privatepaste.com
I'm sorry that I'm not familiar with PostgreSQL. My solution is in MySQL, I hope it can help since if they (MySQL & PostgreSQL) are same.
First, we should add 1 more field into your batch_main table to track the origin batch_temp record for each batch_main record.
ALTER TABLE `batch_main`
ADD COLUMN tempid bigint;
Then, on approval, we will insert 5k rows by 1 query:
INSERT INTO batch_main
(batchid, userid, amount, tempid)
SELECT batchid, userid, amount, amount_id FROM batch_temp;
So, with each new batch_main record we have its origin batch_temp record's id. Then, insert the detail records
INSERT INTO `batch_main_detail`
(detail_amount, detail_mainid)
SELECT
btd.detail_amount, bm.amount_id
FROM
batch_temp_detail `btd`
INNER JOIN batch_main `bm` ON btd.detail_tempid = bm.tempid
Done!
P/S:
I'm confuse a bit about the way you name your fields, and since I do not know about PostgreSQL and by looking into your syntax, can you use same sequence for primary key of both table batch_temp & batch_main? If you can, it's no need to add 1 more field.
Hope this help,
Simply need to update your Schema. Instead of having two tables: one main and one temporary, you should have all the data in main table, but have a flag which indicates whether a certain record is approved or no. Initially it will be set to false, and once approved it will simply be set to true and then the data can display on your website etc. That way you will not need to write the data two times, or even have to move it from one table to another
You haven't specified RDBMS you are using, but good old INSERT with SELECT in it must do the trick in one command:
insert main (field1,...,fieldN) select field1,...,fieldN from temporary
In a customer CMS the customer can update their personal information, like change their address and first/last name. I use a mysql UPDATE query for that.
Problem with working like this is, is that people can change their information. E.g. change their name from john doe to asdfdas. I would like to SAVE their old information.
What are my options? What is the best way to do this?
Assuming the user has a unique ID you could have an old_user_information table and when you do an update also do a new entry into that table. The table would have an autogenerated ID as well as the unique user ID and the rest of that users past information.
A user could have multiple rows in this table but only one row in the real Users table.
Edit: If I were you I would write a stored procedure that does both of these things so that it is easier to manage if things change.
You can make table that contains something like this
`yourTableID, field, value, date`
and update this with a trigger. You write an update trigger that adds the old value if it is changed. Look at the manual here to find out more about triggers.
If you don't want to use triggers you could obviously do the same in your logic: just update the history table with the old value. But this needs some trickery to find out if you need to update it, but nothing to complicated.
For easy retrieval what happened you might want to add something like "oldvalue" AND "newvalue", but the latter isn't really needed, as it is either in the next update as 'old' value, or it is the current value.
Create new columns for the data being updated column would be prior_to_update_column
On update, move the old info into prior_to_update_column
If the user updates again, append to the prior_to_update_column seperated by , (to look like an array).
This should keep all the previous info the user updates
add an additional field name version
and use Insert instead of update
あの答えのとうりに、やってない。
UPDATE table name SET column=column+'new value' WHERE condition
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 a MySQL database where I am storing information that is entered from a PHP web page. I have a page that allows the user to view an existing row, and make changes and save them to the database. I want to know the best way to keep the original entries, as well as the new update and any subsequent updates.
My thought is to make a new table with the same columns as the first, with an additional timestamp field. When a user submits an update, the script would take the contents of the main table's row, and enter them into the archive table with a timestamp when it was done, and then enter in the new values to the main table. I'd also add a new field to the main table to specify whether or not the row has ever been edited.
This way, I can do a query of the main table and get the most current data, and I can also query the archive table to see the change history. Is this the best way to accomplish this, or is there a better way?
You can use triggers on update, delete, or insert to keep track of all changes, who made them and at what time.
Lookup database audit tables. There are several methods, I like the active column which gets set to 0 when you 'delete' or 'update' and the new record gets inserted. It does make a headache for unique key checking. The alternative I've used is the one you have mentioned, a separate table.
As buckbova mentions you can use a trigger to do the secondary insert on 'delete' or 'update'. Otherwise manage it in your PHP code if you don't have that ability.
You don't need a second table. Just have a start and end date on each row. The row without an end date is the active record. I've built entire systems using this method, and just so long as you index the date fields, it's very fast.
When retrieving the current record, AND end_date IS NULL gets added to the WHERE clause.
In this situation, I would recommend you to consider all properties in one table after adding it few columns:
active/ not active
ID of the person who kept these parameters
timestamp of adding
How can we re-use the deleted id from any MySQL-DB table?
If I want to rollback the deleted ID , can we do it anyhow?
It may be possible by finding the lowest unused ID and forcing it, but it's terribly bad practice, mainly because of referential integrity: It could be, for example, that relationships from other tables point to a deleted record, which would not be recognizable as "deleted" any more if IDs were reused.
Bottom line: Don't do it. It's a really bad idea.
Related reading: Using auto_increment in the mySQL manual
Re your update: Even if you have a legitimate reason to do this, I don't think there is an automatic way to re-use values in an auto_increment field. If at all, you would have to find the lowest unused value (maybe using a stored procedure or an external script) and force that as the ID (if that's even possible.).
You shouldn't do it.
Don't think of it as a number at all.
It is not a number. It's unique identifier. Think of this word - unique. No record should be identified with the same id.
1.
As per your explanation provided "#Pekka, I am tracking the INsert Update and delete query..." I assume you just some how want to put your old data back to the same ID.
In that case you may consider using a delete-flag column in your table.
If the delete-flag is set for some row, you shall consider program to consider it deleted. Further you may make it available by setting the delete-flat(false).
Similar way is to move whole row to some temporary table and you can bring it back when required with the same data and ID.
Prev. idea is better though.
2.
If this is not what you meant by your explanation; and you want to delete and still use all the values of ID(auto-generated); i have a few ideas you may implement:
- Create a table (IDSTORE) for storing Deleted IDs.
- Create a trigger activated on row delete which will note the ID and store it to the table.
- While inserting take minimum ID from IDSTORE and insert it with that value. If IDSTORE is empty you can pass NULL ID to generate Auto Incremented number.
Of course if you have references / relations (FK) implemented, you manually have to look after it, as your requirement is so.
Further Read:
http://www.databasejournal.com/features/mysql/article.php/10897_2201621_3/Deleting-Duplicate-Rows-in-a-MySQL-Database.htm
Here is the my case for mysql DB:
I had menu table and the menu id was being used in content table as a foreign key. But there was no direct relation between tables (bad table design, i know but the project was done by other developer and later my client approached me to handle it). So, one day my client realised that some of the contents are not showing up. I looked at the problem and found that one of the menu is deleted from menu table, but luckily the menu id exist in cotent table. I found the menu id from content table that was deleted and run the normal insert query for menu table with same menu id along with other fields. (Id is primary key) and it worked.
insert into tbl_menu(id, col1, col2, ...) values(12, val1, val2, ...)