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
Related
I am trying to create a database using python to execute the SQL commands (for CS50x problem set 7).
I have created a table with an id field set to AUTO_INCREMENT, but the field in the database is populated only by NULL values. I just want it to have an incrementing id starting at 1.
I've tried searching online to see if I'm using the right syntax and can't find anything obvious, nor can I find someone else with a similar problem, so any help would be much appreciated.
Here is the SQL command I am running:
# For creating the table
db.execute("""
CREATE TABLE students (
id INTEGER AUTO_INCREMENT PRIMARY KEY,
first_name VARCHAR(255) NOT NULL,
middle_name VARCHAR(255) DEFAULT (NULL),
last_name VARCHAR(255) NOT NULL,
house VARCHAR(10),
birth INTEGER
);
""")
# An example insert statement
db.execute("""
INSERT INTO students (
first_name,
middle_name,
last_name,
house,
birth
)
VALUES (
?, ?, ?, ?, ?
);
""", "Harry", "James", "Potter", "Gryffindor", 1980)
Here is a screenshot of the database schema shown in phpliteadmin :
And here is a screenshot of the resulting database:
My guess is that you are using SQLite with phpliteadmin and not MySql, in which case this:
id INTEGER AUTO_INCREMENT PRIMARY KEY
is not the correct definition of the auto increment primary key.
In fact, the data type of this column is set to INTEGER AUTO_INCREMENT, as you can see in phpliteadmin, which according to 3.1. Determination Of Column Affinity, has INTEGER affinity.
Nevertheless it is the PRIMARY KEY of the table but this allows NULL values.
The correct syntax to have an integer primary key is this:
id INTEGER PRIMARY KEY AUTOINCREMENT
This cannot happen, if your statements are executed correctly.
I notice that you are not checking for errors in your code. You should be doing that!
My guess is that the table is already created without the auto_increment attribute. The create table is generating an error and you are inserting into the older version.
You can fix this by dropping the table before you create it. You should also modify the code to check for errors.
I've found a way to find missing tables between two databases, and missing columns from intersect tables. I can get "create" syntax for missing tables, but how do I generate "alter" syntax for missing columns?
Is there something like SHOW CREATE TABLE $table for column?
#Edit
I get:
CREATE TABLE `table` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(225) NOT NULL DEFAULT '',
PRIMARY KEY (`id`)
)
by SHOW CREATE TABLE $table
-> I figure out the second database's "table" misses "name" column. How do I "parse" (?) this create to generate alter to add column "name" to the second database's table?
If you want individual columns, then use ( change users to your table name )
show columns from users
If this is done on both tables, you can check the differences. This may include having to alter columns if the definition has changed.
To add a new column, use something like
alter table users add column email varchar(255) after name
The after bit allows you to position the new column at the same place as in your other table (makes it look consistent in query tools).
I currently am working on some project that insert a lot of data into some tables. To ensure that my system is fast enough, I want to fragment my huge table into some smaller tables representing the months data. I have an idea of how it will work, but I still need some more informations.
The primary keys of my tables must be continuous so I thought of an architecture that would look like this:
CREATE TABLE `foo` (
`id` bigint(11) unsigned NOT NULL AUTO_INCREMENT,
}
CREATE TABLE `foo012014` (
`id` bigint(11),
`description` varchar(255),
}
CREATE TABLE `foo022014` (
`id` bigint(11),
`description` varchar(255),
}
On every insertion, the PHP page will look if a table already exists for the month and if not will create it.
The thing is, how do I get to bind the "foo" child table primary key to the "foo" mother table? Plus, is this design a bad practice or is it good?
It's not a good pratice, and difficult your queries.
With just the id you already have an index, which allows for better indexing of your data.
If your queries are also nicely written and organized, the time to execute a query in your database will be relatively small with 1 million rows or 20.
Solutions
First
For a better maintenance I recommend the following:
Add a new field in your table food: created datetime DEFAULT CURRENT_TIMESTAMP (works in MySQL 5.6+, for other versions, or set manually in every insert, or change to timestamp)
And, just use this field for group your data basead in datetime values, like that: 2014-01-24 13:18.
It's easy to select and manipulate.
Second
Create a external table with month and year, like that:
drop table if exists foo_periods;
create table foo_periods (
id int not null auto_increment primary key,
month smallint(4) not null,
year smallint(4) not null,
created datetime,
modified datetime,
active boolean not null default 1,
index foo_periods_month (month),
index foo_periods_year (year)
);
You can change smallint in month to varchar if you feels better.
Then, just create a FK, and done!
ALTER TABLE foo
ADD COLUMN foo_period_id int not null;
ALTER TABLE foo
ADD CONSTRAINT foo_foo_period_id
FOREIGN KEY (foo_period_id)
REFERENCES foo_periods (id);
References
If you want read more about fragmentation / optimization in MySQL, this is a great post.
I have a create database and have about 8 tables in Database also created Primary keys and foreign-keys in appropriate tables. But when I insert data in primary-table, my other table doesn't show updated data.
I mean, say I have a table which has data for names like ;
N is (name)
N1 = George, N2 = Ross, N3 = Rim ...etc now that means i have Primary key N1,N2,N3 etc..
Now, when I insert this primary keys in others table it should shows me name like George, ross and rim instead of primary-key number it self(N1,N2,N3).
How can I get names instead PK itself?
You are misunderstanding the concept of keys in relational databases. Keys are there, not to copy data from similar tables but to show the relations between data in different tables. They help to understand how the data between different tables is related - that is where the name "relational database" comes from. They also speed up querying of that data if indexed.
You can read more about the usage of keys here: Keys and normalization
I am still unclear on what exactly you want to do with the database. but let me demonstrate you on the basic of database and how you should be using it. Consider a table users where you will be storing the data related to user.
CREATE TABLE `users` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(50) NOT NULL,
`email` varchar(50) DEFAULT NULL,
`phone` varchar(30) DEFAULT NULL,
PRIMARY KEY (`id`),
);
the column id holds the primary key and have an attribute called auto_increment, now what this means is every time you insert a record to this table the id attribute gets incremented and you don't have to worry about inserting any value in this column because your database will take care of that. for example take a look at insert query below.
INSERT INTO users(name,email,phone) VALUES('First Name', 'first#domain.com', '9999999999');
INSERT INTO users(name,email,phone) VALUES('Second Name', 'second#domain.com', '8888888888');
INSERT INTO users(name,email,phone) VALUES('Third Name', 'third#domain.com', '2222222222');
INSERT INTO users(name,email,phone) VALUES('Fourth Name', 'fourth#domain.com', '3333333333');
did you see you did not insert any id here. this is because it is database who will handle the logic. now the first record will hold the value 1 the second will have 2 the third one 3 and the fourth one 4 and so on.
hope this helps you.
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