Question on preventing duplicated entry in my simple web form.
My table record user input from a web form, and distinguished by date e.g. DATE(). How to prevent user with the same name to enter information twice in a single date, e.g. same username cannot be entered twice in the same date, but can be entered at other date?
Your table should have these:
create table tablename (
...
user_id bigint, -- or whatever
date_created date,
unique key(user_id, date_created)
...
);
You can simple create a composite primary key. For your case this means that your primary key must consists of a date field as well as the username field.
In several ways.
First, you can create index on your table. (i'm using simple table as an example).
CREATE TABLE `test` (
`id` INT NOT NULL ,
`name` VARCHAR( 255 ) NOT NULL ,
`date` DATE NOT NULL ,
PRIMARY KEY ( `id` )
) ENGINE = MYISAM;
ALTER TABLE `test` ADD UNIQUE (
`name` ,
`date`
);
This is MySQL way.
You also should make checks in PHP ,although you can do it when inserting (MySQL will return error and you can check it). But you can make additional SELECT before inserting (SELECT * from test WHERE name=USER AND date=DATE) and check record count. If it's more than 0, you show error.
When saving, you seldom should worry about one additional SQL. If you should, just check MySQL statement for errors (MySQL way :)).
Create a unique key on the user and date column
http://dev.mysql.com/doc/refman/5.1/en/create-table.html
Related
I have a problem inserting data into my MySQL database.
The structure of the db looks like this:
id | name | class | 23-02-2022 | 26-02-2022 | and so on ...
The databse is part of an attendance system. So I use dates as column names.
I use this code to open a csv file and upload some data into the db. As you can see in this part of the code I only put datas in the name and class column.
if (($handle = fopen("class.csv", "r")) !== FALSE)
{
while (($data = fgetcsv($handle, 1000, ";")) !== FALSE)
{
$query="INSERT INTO table21228 (name, class) VALUES ('$data[0]' , '$data[1]')";
if ($conn->query($query) === TRUE) {
}
else {
echo 'Error: '. $conn->error;
} fclose($handle);
}
I get this error message: Error: Field '23-02-2022' doesn't have a default value
When I use a different table, where the only columns are id, name, class it works without any problems.
So I guess the structure of my db must be the problem
Maybe all those dates columns like 23-02-2022???
Hope some might help me. Thank you!
Kind regards
Dan
The problem is that the columns of the dates dont have a DEFAULT value and since while adding a record you dont define a value for the column it is giving an error. The solution is that either you give a value for the columns while adding the records or else alter the columns and give it a default value.
But your Table structure is not at all feasible to use. You should not have columns for individual dates. Like this you will have infinite columns in your table. So instead the solution is that you insert the date of the attendance marked with the rows you add.
Could be you have a table with not null columns and you try to insert a row without a proper value for the not nullable columns .. the you have the message for field '23-02-2022' doesn't have a default value
the try insert a proper value for these columns
$query="INSERT INTO table21228 (name, class, `23-02-2022`, `26-02-2022` ) VALUES ('$data[0]' , '$data[1]', '2022-02-20', '2022-02-20')";
or try revoke the not null constranits for theese columns
alter table table21228 modify column `23-02-2022` date;
or set a default value
ALTER TABLE table21228 MODIFY column `23-02-2022` date DEFAULT '2022-02-20';
The problem is, that you try to insert a row into a table where not all columns do have a default value. You either need to give all columns a default value (using ALTER TABLE or a modified CREATE TABLE) or you have to mention all those columns in your INSERT query.
Also, your code is vulnerable to SQL injection. Read this great guide on how to prevent that:
https://phpdelusions.net/pdo
If your table looks like this:
CREATE TABLE `attendances` (
`id` INT NOT NULL AUTO_INCREMENT,
`name` VARCHAR(250) NOT NULL,
`class` VARCHAR(250) NOT NULL,
`23-02-2022` INT NOT NULL,
`26-02-2022` INT NOT NULL,
PRIMARY KEY (`id`)) ENGINE = InnoDB;
You can change it like this:
ALTER TABLE `attendances`
CHANGE `23-02-2022` `23-02-2022` INT NULL DEFAULT NULL;
or
ALTER TABLE `attendances`
CHANGE `26-02-2022` `26-02-2022` INT NOT NULL DEFAULT '0';
Here, 23-02-2022 has a default value of "NULL" and 26-02-2022 is an example with a default value of "0". Or just create the table correctly in the first place:
CREATE TABLE `attendances` (
`id` INT NOT NULL AUTO_INCREMENT,
`name` VARCHAR NOT NULL,
`class` VARCHAR NOT NULL,
`23-02-2022` INT NULL DEFAULT NULL,
`26-02-2022` INT NOT NULL DEFAULT '0',
PRIMARY KEY (`id`)) ENGINE = InnoDB;
As an alternative, you could just add all columns that have no default value to your INSERT query:
INSERT INTO `attendances` (
`id`, `name`, `class`, `23-02-2022`, `26-02-2022`
) VALUES (
NULL, 'name1', 'class1', '0', '0'
);
Make sure to protect your app from SQL injection:
<?php
$pdo->prepare("
INSERT INTO `attendances` (
`id`, `name`, `class`, `23-02-2022`, `26-02-2022`
) VALUES (
NULL, ?,?,?,?
)
")->execute(['name1', 'class1', 0, 0]);
So I use dates as column names.
...bad idea, because you theoretically have an infinite number of columns, if the system is used long term. And it will make it very difficult to write certain types of query to understand the data.
So I guess the structure of my db must be the problem
...essentially, yes.
To understand how to design your database correctly, you should learn about database normalisation.
In this scenario I'd suggest you'd have one table for the list of all people, and another for the list of all classes.
If you're running a predetermined timetable, you might then have a table which lists the class, the date and the teacher assigned to that date & class. (Or you might assign the teacher in the classes table, if one teacher normally takes the whole class.)
Then lastly you'd have a separate "attendance" table which contains columns "personID" and "attendanceDate", and "classID".
That way you will end up with multiple rows in there with the same person / class combination and different dates, to record all their attendances at each class and each date of that class. And it's completely extendable, infinitely, without you needing to modify the tables each time a new class or date is announced, or needing to dervice column names in your code when trying to generate a query.
first check your csv file has the right amount of columns as your database then set your columns default to from not NULL to null or none
I have a table where I log members.
There are 1,486,044 records here.
SELECT * FROM `user_log` WHERE user = '1554143' order by id desc
However, this query takes 5 seconds. What do you recommend ?
Table construction below;
CREATE TABLE IF NOT EXISTS `user_log` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`user` int(11) NOT NULL,
`operation_detail` varchar(100) NOT NULL,
`ip_adress` varchar(50) NOT NULL,
`l_date` datetime NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
COMMIT;
For this query:
SELECT * FROM `user_log` WHERE user = 1554143 order by id desc
You want an index on (user, id desc).
Note that I removed the single quotes around the filtering value for user, since this column is a number. This does not necessarily speeds things up, but is cleaner.
Also: select * is not a good practice, and not good for performance. You should enumerate the columns you want in the resultset (if you don't need them all, do not select them all). If you want all columns, since your table has not a lot of columns, you might want to try a covering index on all 5 columns, like: (user, id desc, operation_detail, ip_adress, l_date).
In addition to the option of creating an index on (user, id), which has already been mentioned, a likely better option is to convert the table to InnoDB as create an index only on (user).
Well, I have this attendance system who mark an attendance every day, well what I am looking is for a restriction other than PHP code like a restriction that can restrict users to enter duplicate record over time.
For e.g I have already marked my attendance .myself
DATE 22-05-2018 and trackingid = 1
if I try to insert mark attendance one more time it should not insert the statement.
It can be done via php and its a long code and i mean like it is possible but is there any way around with MySQL , through which we can make 2 columns unique if they both already exist just dont let user insert .
Use unique_index on your columns
ALTER TABLE `tablename` ADD UNIQUE `unique_index`(`columnOneName`, `columnTwoName`);
You can also use the following like sql while creating your table:-
CREATE TABLE `tableName` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`columnOne` int(11) DEFAULT NULL,
`columnTwo` int(11) DEFAULT NULL,
`columnThree` varchar(128),
PRIMARY KEY (`id`),
UNIQUE KEY `columnOne_columnTwo_unique_index` (`id_box_elements`,`id_router`)
);
I'm using php and i have a table that have 2 column of varchar , one is used for user identification, and the other is used for page name entry.
they both must be varchar.
i want to insert ignore data when user enter a page to know if he visited it or not, and i want to fetch all the rows that the user have been in.
fetch all for first varchar column.
insert if not exist for both values.
I'm hoping to do it in the most efficient way.
what is the best way to insert without checking with another query if exist?
what is the best way other then:
SELECT * FROM table WHERE id = id
to fetch when the column needed is varchar?
You should consider a normalized table structure like this:
CREATE TABLE user (
id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(100)
);
CREATE TABLE page (
id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(100)
);
CREATE TABLE pages_visted (
id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
user_id INT UNSIGNED,
page_id INT UNSIGNED,
UNIQUE KEY (user_id, page_id)
);
INSERT IGNORE INTO pages_visted (user_id, page_id) VALUES (:userId, :pageId);
SELECT page_id FROM pages_visted WHERE user_id = :userId;
I think you want to implement a composite primary key.
A composite primary key tells MySQL that you want your primary key to be a combination of fields.
More info here: Why use multiple columns as primary keys (composite primary key)
I don't know of a better option for your query, although I can advise, if possible:
Define columns to be NOT NULL. This gives you faster processing and requires less storage. It will also simplify queries sometimes because you don't need to check for NULL as a special case.
And with variable-length rows, you get more fragmentation in tables where you perform many deletes or updates due to the differing sizes of the records. You'll need to run OPTIMIZE TABLE periodically to maintain performance.
I have the following schema with the following attributes:
USER(TABLE_NAME)
USER_ID|USERNAME|PASSWORD|TOPIC_NAME|FLAG1|FLAG2
I have 2 questions basically:
How can I make an attribute USER_ID as primary key and it should
automatically increment the value each time I insert the value into
the database.It shouldn't be under my control.
How can I retrieve a record from the database, based on the latest
time from which it was updated.( for example if I updated a record
at 2pm and same record at 3pm, if I retrieve now at 4pm I should get
the record that was updated at 3pm i.e. the latest updated one.)
Please help.
I'm assuming that question one is in the context of MYSQL. So, you can use the ALTER TABLE statement to mark a field as PRIMARY KEY, and to mark it AUTOINCREMENT
ALTER TABLE User
ADD PRIMARY KEY (USER_ID);
ALTER TABLE User
MODIFY COLUMN USER_ID INT(4) AUTO_INCREMENT; -- of course, set the type appropriately
For the second question I'm not sure I understand correctly so I'm just going to go ahead and give you some basic information before giving an answer that may confuse you.
When you update the same record multiple times, only the most recent update is persisted. Basically, once you update a record, it's previous values are not kept. So, if you update a record at 2pm, and then update the same record at 3pm - when you query for the record you will automatically receive the most recent values.
Now, if by updating you mean you would insert new values for the same USER_ID multiple times and want to retrieve the most recent, then you would need to use a field in the table to store a timestamp of when each record is created/updated. Then you can query for the most recent value based on the timestamp.
I assume you're talking about Oracle since you tagged it as Oracle. You also tagged the question as MySQL where the approach will be different.
You can make the USER_ID column a primary key
ALTER TABLE <<table_name>>
ADD CONSTRAINT pk_user_id PRIMARY KEY( user_id );
If you want the value to increment automatically, you'd need to create a sequence
CREATE SEQUENCE user_id_seq
START WITH 1
INCREMENT BY 1
CACHE 20;
and then create a trigger on the table that uses the sequence
CREATE OR REPLACE TRIGGER trg_assign_user_id
BEFORE INSERT ON <<table name>>
FOR EACH ROW
BEGIN
:new.user_id := user_id_seq.nextval;
END;
As for your second question, I'm not sure that I understand. If you update a row and then commit that change, all subsequent queries are going to read the updated data (barring exceptionally unlikely cases where you've set a serializable transaction isolation level and you've got transactions that run for multiple hours and you're running the query in that transaction). You don't need to do anything to see the current data.
(Answer based on MySQL; conceptually similar answer if using Oracle, but the SQL will probably be different.)
If USER_ID was not defined as a primary key or automatically incrementing at the time of table creation, then you can use:
ALTER TABLE tablename MODIFY USER_ID INT NOT NULL PRIMARY KEY AUTO_INCREMENT;
To issue queries based on record dates, you have to have a field defined to hold date-related datetypes. The date and time of record modifications would be something you would manage (e.g. add/change) based on the way in which you are accessing the records (some PHP-related way? it's unclear what scripts you have in play, based on your question.) Once you have dates in your records you can ORDER BY the date field in your SELECT query.
Check this out
For your AUTOINCREMENT, Its a question already asked here
For your PRIMARY KEY use this
ALTER TABLE USER ADD PRIMARY KEY (USER_ID)
Can you provide more information. If the value gets updated you definitely do NOT have your old value that you entered at 2pm present in the dB. So querying for it will be fine
You can use something like this:
CREATE TABLE IF NOT EXISTS user (
USER_ID unsigned int(8) NOT NULL AUTO_INCREMENT,
username varchar(25) NOT NULL,
password varchar(25) NOT NULL,
topic_name varchar(100) NOT NULL,
flag1 smallint(1) NOT NULL DEFAULT 0,
flag2 smallint(1) NOT NULL DEFAULT 0,
update_time TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (uid)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
For selection use query:
SELECT * from user ORDER BY update_time DESC