I am making a system where users can upload any file they want, and not use it to execute any kind of code. As a part of that, I rename every file, and store its original name in a MySQL table. This table contains the id of the user who uploaded it, and a unique id of the upload. Currently I am doing it like this:
CREATE TABLE `uploads` (
`user_id` INT(11) NOT NULL,
`upload_id` INT(11) NOT NULL AUTO_INCREMENT,
`original_name` VARCHAR(30) NOT NULL,
`mime_type` VARCHAR(30) NOT NULL,
`name` VARCHAR(50) NOT NULL,
PRIMARY KEY (`user_id`, `upload_id`)
) ENGINE=MyISAM;
This means I will always have a unique combination of user_id and upload_id, and every users first upload has an id of 1. However I want to use a foreign key for the user_Id, so if I delete a user, its uploads would also be deleted. This means I have to do it in InnoDB. How would i go about that, since the above setup only works in MyISAM.
My users table (wich i would get user_id from) looks like this:
CREATE TABLE `".DATABASE."`.`users` (
`user_id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
`username` VARCHAR(30) NOT NULL,
`email` VARCHAR(50) NOT NULL,
`password` CHAR(128) NOT NULL,
`salt` CHAR(128) NOT NULL
) ENGINE = InnoDB;
What i want is for the uploads table to look like this:
user_id | upload_id
1 | 1
1 | 2
2 | 1
2 | 2
2 | 3
1 | 3
If that makes sense
If I understood correctly:
Replace the primary key to a unique index with the two fields. Make the upload_id the primary key and user_id the foreign key then.
Unfortunately for this problem, the auto increment column will not start over at 1 for each user. It will just increment for each added row, regardless of any particular column value.
Edit: displaying my ignorance there, MyISAM tables apparently will start over at 1 for each user when a multi-column index this way. https://dev.mysql.com/doc/refman/5.0/en/example-auto-increment.html
Fortunately, it is probably not necessary for upload_id to start at 1 for each user. Using auto increment on that column means you will always have a unique combination of user_id and upload_id even without using both columns as the primary key, or even creating a unique index, because every record will have a different upload_id. You should still be able to implement the cascade delete with this setup.
Related
I want to create a table like below:
id| timestamp | neighbour1_id | neighbour1_email | neighbour2_id | neighbour2_email
and so on upto max neighbour 20.
I have two questions:
Should I create columns statically or is there a way to create columns dynamically using php based on the count of json Array?
In either case, how would I refer to the columns dynamically and assign value to them based on jsonArray?
My jsonArray would look something like:
{id:123, email_id:abc, neighbours: [{neighbour1_id:234, neighbour1_email: bcd}, {neighbour2_id:345, neighbour2_email:dsf}, {}, {}...]}
Please advice. Thanks.
It looks like you need to rethink your database structure a bit. To me it looks like you need a single users (or whatever they are) table:
CREATE TABLE `users` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`email` varchar(255) NOT NULL,
`cretaed_at` timestamp NOT NULL,
PRIMARY KEY (`id`)
);
And another table that defines relations between those users:
CREATE TABLE `neighbors` (
`parent` int(11) unsigned NOT NULL,
`child` int(11) unsigned NOT NULL,
PRIMARY KEY (`parent`,`child`)
);
Now you can add as many neighbors to each user as you want. Fetching them is as easy as:
SELECT * FROM `users`
LEFT JOIN `neighbors` ON `users`.`id` = `neighbors`.`child`
WHERE `neighbors`.`parent` = ?
Where that question mark would become the id of the user from which you are fetching the neighbors, preferably by using a prepared statement.
If it is all JSON you will be working with, and querying isn't much of an issue, you could consider working with a noSql database or document store (like redis or mongoDb), but that is an entirely different story.
Just repeating a bunch of columns x times is definitely not the way to go. Vertical size (# rows) of tables in relational databases is no big issue, they are designed for that. Horizontal size (# columns) however is something to be careful with, as it may make your db uanessacry large, and decrease performance.
Just consider what you would if you want to find a user that has a neighbor with an email address [x]. You would have to repeat your where statement 20 times for each possible email column. And that is just one example...
well, the answer i was working on while pevara was posting theirs faster is almost the same...
CREATE TABLE `neighbours` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`neighbour_email` char(64) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8;
CREATE TABLE `neighbour_email_collections` (
`id` int(10) unsigned NOT NULL,
`email_id` char(64) NOT NULL,
`neighbour_id` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`,`neighbour_id`)
) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8;
insert into neighbours values (234, "bcd");
insert into neighbours values (345, "dsf");
insert into neighbour_email_collections values(123, "abc", 234);
insert into neighbour_email_collections values(123, "abc", 345);
select *
from neighbours
left join neighbour_email_collections
on neighbour_email_collections.neighbour_id=neighbours.id
where neighbour_email_collections.id=123;
I got my table like this:
`id` int(10) NOT NULL AUTO_INCREMENT,
`email` varchar(50) NOT NULL,
`role` varchar(10),
PRIMARY KEY (`id`),
UNIQUE KEY `username` (`email`)
and I have data like this
1 | admin | 702a7853691c23ec922e408b1322d2cc4fa1d101 | name#doman.sk | guest
I try to SELECT data:
$row = $this->database->table('users')->where('username', $username)->fetch();
I can access:
$row->email,$row->username,$row->password
but i can't access :
$row->role
I can't find sollution for this.
I don't know you are using which mvc or cms. But i know that after each select you must fetch your data. See your documents for fetch syntax.
I have a problem while designing my database and I don't know how to solve it:
i have following table (relevant columns):
CREATE TABLE IF NOT EXISTS `prmgmt_tasks` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(300) NOT NULL,
`project_id` int(11) NOT NULL,
);
What I want: every task has a unique id (autoincrement). The name of the task is not unique, but it should be unique for each project. For example "Design userinterface" can occur in project with id 1 and 2, but not twice in project with id 1. Something like 'unique for: group by project_id'.
Of course, I could check that in every query, but I am looking for a way to model this in the database, so it will allways be consistent, no matter what queries are executed.
Thanks for help!
Create a unique composite index on the combined fields.
CREATE UNIQUE INDEX tasks_name_project
ON prmgmt_tasks (name, project_id);
I am trying to alter a table which has no primary key nor auto_increment column. I know how to add an primary key column but I was wondering if it's possible to insert data into the primary key column automatically (I already have 500 rows in DB and want to give them id but I don't want to do it manually). Any thoughts? Thanks a lot.
An ALTER TABLE statement adding the PRIMARY KEY column works correctly in my testing:
ALTER TABLE tbl ADD id INT PRIMARY KEY AUTO_INCREMENT;
On a temporary table created for testing purposes, the above statement created the AUTO_INCREMENT id column and inserted auto-increment values for each existing row in the table, starting with 1.
suppose you don't have column for auto increment like id, no, then you can add using following query:
ALTER TABLE table_name ADD id int NOT NULL AUTO_INCREMENT primary key FIRST
If you've column, then alter to auto increment using following query:
ALTER TABLE table_name MODIFY column_name datatype(length) AUTO_INCREMENT PRIMARY KEY
For those like myself getting a Multiple primary key defined error try:
ALTER TABLE `myTable` ADD COLUMN `id` INT AUTO_INCREMENT UNIQUE FIRST NOT NULL;
On MySQL v5.5.31 this set the id column as the primary key for me and populated each row with an incrementing value.
In order to make the existing primary key as auto_increment, you may use:
ALTER TABLE table_name MODIFY id INT AUTO_INCREMENT;
Yes, something like this would do it, it might not be the best though. You might wanna make a backup:
$get_query = mysql_query("SELECT `any_field` FROM `your_table`");
$auto_increment_id = 1;
while($row = mysql_fetch_assoc($get_query))
{
$update_query = mysql_query("UPDATE `your_table` SET `auto_increment_id`=$auto_increment_id WHERE `any_field` = '".$row['any_field']."'");
$auto_increment_id++;
}
Notice that the the any_field you select must be the same when updating.
The easiest and quickest I find is this
ALTER TABLE mydb.mytable
ADD COLUMN mycolumnname INT NOT NULL AUTO_INCREMENT AFTER updated,
ADD UNIQUE INDEX mycolumnname_UNIQUE (mycolumname ASC);
I was able to adapt these instructions take a table with an existing non-increment primary key, and add an incrementing primary key to the table and create a new composite primary key with both the old and new keys as a composite primary key using the following code:
DROP TABLE IF EXISTS SAKAI_USER_ID_MAP;
CREATE TABLE SAKAI_USER_ID_MAP (
USER_ID VARCHAR (99) NOT NULL,
EID VARCHAR (255) NOT NULL,
PRIMARY KEY (USER_ID)
);
INSERT INTO SAKAI_USER_ID_MAP VALUES ('admin', 'admin');
INSERT INTO SAKAI_USER_ID_MAP VALUES ('postmaster', 'postmaster');
ALTER TABLE SAKAI_USER_ID_MAP
DROP PRIMARY KEY,
ADD _USER_ID INT AUTO_INCREMENT NOT NULL FIRST,
ADD PRIMARY KEY ( _USER_ID, USER_ID );
When this is done, the _USER_ID field exists and has all number values for the primary key exactly as you would expect. With the "DROP TABLE" at the top, you can run this over and over to experiment with variations.
What I have not been able to get working is the situation where there are incoming FOREIGN KEYs that already point at the USER_ID field. I get this message when I try to do a more complex example with an incoming foreign key from another table.
#1025 - Error on rename of './zap/#sql-da07_6d' to './zap/SAKAI_USER_ID_MAP' (errno: 150)
I am guessing that I need to tear down all foreign keys before doing the ALTER table and then rebuild them afterwards. But for now I wanted to share this solution to a more challenging version of the original question in case others ran into this situation.
Export your table, then empty your table, then add field as unique INT, then change it to AUTO_INCREMENT, then import your table again that you exported previously.
You can add a new Primary Key column to an existing table, which can have sequence numbers, using command:
ALTER TABLE mydb.mytable ADD pk_columnName INT IDENTITY
I was facing the same problem so what I did I dropped the field for the primary key then I recreated it and made sure that it is auto incremental . That worked for me . I hope it helps others
ALTER TABLE tableName MODIFY tableNameID MEDIUMINT NOT NULL AUTO_INCREMENT;
Here tableName is name of your table,
tableName is your column name which is primary has to be modified
MEDIUMINT is a data type of your existing primary key
AUTO_INCREMENT you have to add just auto_increment after not null
It will make that primary key auto_increment......
Hope this is helpful:)
Well, you have multiple ways to do this:
-if you don't have any data on your table, just drop it and create it again.
Dropping the existing field and creating it again like this
ALTER TABLE test DROP PRIMARY KEY, DROP test_id, ADD test_id int AUTO_INCREMENT NOT NULL FIRST, ADD PRIMARY KEY (test_id);
Or just modify it
ALTER TABLE test MODIFY test_id INT AUTO_INCREMENT NOT NULL, ADD PRIMARY KEY (test_id);
How to write PHP to ALTER the already existing field (name, in this example) to make it a primary key? W/o, of course, adding any additional 'id' fields to the table..
This a table currently created - Number of Records found: 4 name VARCHAR(20) YES
breed VARCHAR(30) YES
color VARCHAR(20) YES
weight SMALLINT(7) YES
This an end result sought (TABLE DESCRIPTION) -
Number of records found: 4
name VARCHAR(20) NO PRI
breed VARCHAR(30) YES
color VARCHAR(20) YES
weight SMALLINT(7) YES
Instead of getting this -
Number of Records found: 5
id int(11) NO PRI
name VARCHAR(20) YES
breed VARCHAR(30) YES
color VARCHAR(20) YES
weight SMALLINT(7) YES
after trying..
$query = "ALTER TABLE racehorses ADD id INT NOT NULL AUTO_INCREMENT FIRST, ADD PRIMARY KEY (id)";
how to get this? -
Number of records found: 4
name VARCHAR(20) NO PRI
breed VARCHAR(30) YES
color VARCHAR(20) YES
weight SMALLINT(7) YES
i.e. INSERT/ADD.. etc. the primary key INTO the first field record (w/o adding an additional 'id' field, as stated earlier.
No existing primary key
ALTER TABLE `db`.`table`
ADD COLUMN `id` INT NOT NULL AUTO_INCREMENT FIRST,
ADD PRIMARY KEY (`id`);
;
Table already has an existing primary key'd column
(it will not delete the old primary key column)
ALTER TABLE `db`.`table`
ADD COLUMN `id` INT NOT NULL AUTO_INCREMENT FIRST,
CHANGE COLUMN `prev_column` `prev_column` VARCHAR(2000) NULL ,
DROP PRIMARY KEY,
ADD PRIMARY KEY (`id`);
;
Note: column must be first for auto increment which is why the FIRST command.
i have a table called users
this what the table look like
CREATE TABLE `users` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`username` varchar(32) NOT NULL,
`password` varchar(60) NOT NULL,
`email` varchar(60) NOT NULL,
PRIMARY KEY (`id`)
)
and finally i have a table called friends,
this what the table look like
CREATE TABLE `friends` (
`friendship_id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`user_id1` bigint(20) unsigned NOT NULL,
`user_id2` bigint(20) unsigned NOT NULL,
`time_created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (`friendship_id`),
KEY `user_id1` (`user_id1`),
KEY `user_id2` (`user_id2`),
CONSTRAINT `friends_ibfk_1` FOREIGN KEY (`user_id1`) REFERENCES `users` (`id`),
CONSTRAINT `friends_ibfk_2` FOREIGN KEY (`user_id2`) REFERENCES `users` (`id`)
)
so basically if userA is following userB , then a row will be added to the friends table, with the attribute user_id1 is userA and user_id2 is userB.
im trying to write a mysql query for a searchbox. the user will enter a string and the query will crawl a list of users that include that string but the people that the user is following need to be displayed first.
so if we have 3 users
jack
jason
john
if the user Chris (who's following jason) enters in the searchbox the string 'ja', the query will crawl the list of users with the following order jason,jack. since jason is followed by chris.
from my understanding , i think it might a group by problem, i tried different queries but i couldnt get the needed results
do you guys have any idea ?
thanks a lot
You have to do a trick for sorting, so friendships get a 0 and non-friendships get a 1 in a temporary field and then we sort ascending for this field and as second we sort by username
SELECT x.username
FROM users x LEFT JOIN friends y ON x.id=y.user_id2 AND y.user_id1=$LOGGED_IN_USER
WHERE LOWER(x.username) LIKE 'ja%'
ORDER BY CASE WHEN y.user_id2 IS NULL THEN 1 ELSE 0 END,x.username
#thanks to scwagner for pointing me to extend JOIN-clause