Hey guys, how the heck do I go about doing this.
I have an address book I'm making and I'm trying to figure out how to tackle my groups. I let the users rename their groups at will. But then this complicates my life ;0
I have 2 tables. groups and contacts the groups has the group names per user. the contacts has a group column that says what group that contact entry belongs to.
How can I rename a group from the groups table and have the new name reflect in the contacts table so everything matches up?
I would suggest changing your model.
Use IDs as primary keys and an intersection-table to assign your contacts to groups:
Groups
id
name
Contacts
id
name
Group_Contacts
group_id -> Groups.id
contact_id -> Contacts.id
Now you can change the group-name whenever you want, without updating the contacts.
EDIT: If you only want to get the contacts of a certain group, use a SELECT like this one:
Select c.name
From groups g
Join group_contacts gc On ( gc.group_id = g.id )
Join contacts c On ( c.id = gc.contact_id )
Where g.name = 'Your group name'
You also could use a before update trigger which first renames all entries in the contacts table to match the new name and then let the update go on
Related
I am working on a project, there has group feature. when I search any group, this time I have to know that am I already join those listed group.
I have group table and another table group user table for adding the user to the group.
I want to get it with SQL query only with one query. How can I do it?
You could try an inner join
SELECT *
FROM Groups
INNER JOIN UserGroup on Groups.Group_ID = UserGroup.Group_ID
I don't know exactly your tables,but it should be something like that.
I have a database table for a user of my website, this table gives each user a user_id.
Using normalization, I have linked the user to a group with a user_group table including user_id and group_id to link a user to a group.
I then have a group table that links a group name to the group_id.
I am trying to output the users on my webpage in a list next to the name of the group, not its id.
I was thinking of using a foreach loop to do this, but the data would need to get into one array? I dont know how I would take the user_id, find out which group _id it it paired with, find out which group name that id was paired with, and then add that to the array with the names and be able to display the group name next to the user's name using foreach.
Thanks for any help.
If i understand you correctly, you want to join you users data to group to show the user details with their group name.
Try out this:
select u.*,g.*,ug.* from users u
left join user_group ug on u.user_id=ug.user_id
left join `group` g on ug.group_id=g.group_id;
From above query you may get blank values for some user's, who are not assigned to any group.
I don't see why a left join is necessary. Should be a regular join unless he wants to display users that don't have groups.
By the way, this is the perfect example of something that should be done in the DB with a select. Pulling everything from these tables and trying to sort through them in java is not a good idea. Maybe I read this post wrong though.
I am creating a site that allows users to view desired 'teams' and can then join them with the click of one button.
I have my users table which contains: user_id, user_name, team_id
Then, I have my teams table which contains: team_id, team_name, team_players
How would I go about having the users to join a group, each user can also only be in 1 team at a time.
If you want each user to be able to join multiple teams, and each team to have multiple users, then you need a "join table."
Table teams_users would contain team_id, user_id. You can make a composite primary key on team_id, user_id (preventing a user from joining the same team twice).
Then you can get a team with:
SELECT * FROM users t1 right join teams_users t2 ON t1.team_id = t2.team_id WHERE t2.team_name = 'the rascals'
Even if you only want players to join one team at a time, you might still want to use the join table in case you ever change your mind. It would be very easy. To only allow one team per user, put a unique constraint on user_id in the join table. If you later decide you want to allow multiple teams, you just remove that constraint.
If a user tries the "join team" action, you simply check for the user_id's existence in the join table.
SELECT * FROM teams_users WHERE user_id = $user_id
If it does exist, you retrieve its matching team_id and tell them, "sorry, you are already in team 'the rascals'. You must leave that team if you want to join another." If they drop their team, you simply do:
DELETE from teams_users WHERE user_id = 5
If they add a team, you just do:
INSERT INTO teams_users ($team_id, $user_id) #// (assuming PHP variables).
The INSERT query will only work if they are not already in a team. If they are you would get an error message. You could also look at "INSERT ON DUPLICATE KEY UPDATE ..." queries. But I would advise against that because you want to warn users before they change teams.
You should start by adding the team_id field to the users table as a foreign key and allow it to be NULL.
Then you would display the team names in an html form with a radio button for each team.
In a PHP file (which should be set to the action of your form) create an if statement based on the values you assigned to each radio button. In each if block, execute a sql UPDATE statement that will add the appropriate group_ID to the right user instance.
I have 5 tables:
user ( user id, user name, etc.. )
role ( role_id, role_name )
user_role ( user_id, roles_id )
form ( form_id, form_name, etc.. )
form_access ( form_id, role_id )
user contains all registered user data.
role contains all different types of roles.
user_role contains which user has which role (all assigned roles are stored)
form contains all form data.
form_access contains data like which user role has which form access(one form can be assigned to many user roles).
I wanted to write a SQL query in PHP to retrieve form name based on the user logged in and his role, e.g. if Admin logs in he should get all forms, if HR logs in he should get forms related to HR only.
I tried this query:
$query = "SELECT ur.role_id, f.form_name, f.form_desc
FROM user_role ur, froms f
WHERE users.id = '".$user."',
users.status ='A',
forms.form_id = form_access.form_id,
from_access.role_id = user_role.role_id,
user_role.role_id = '".$user."'";`
Some one help me out with the correct query?
Since you start from the user_id you'll want to select from user_role and JOIN form_access and form.
SELECT `form`.`form_name` AS `form_name`
FROM `user_role` AS `ur`
INNER JOIN `form_access` AS `fa` ON `fa`.`role_id` = `ur`.`role_id`
INNER JOIN `form` AS `f` ON `f`.`form_id` = `fa`.`form_id`
WHERE `ur`.`user_id` = '".$user."'
PS: Check the table and column names.
You have to use AND .
BUT this should be better with joins.
$query = "SELECT ur.role_id, f.form_name, f.form_desc
FROM from_access
INNER JOIN froms f ON forms.form_id = form_access.form_id
INNER JOIN user_role ur ON from_access.role_id = user_role.role_id
INNER JOIN users ON users.id = user_role.role_id
WHERE users.id = '".$user."'
AND users.status ='A' ";
Your query is entirely broken, the others may have provided you with solutions but I'm going to give you some advice.
You've written an entire query, tried it, and it failed. I write queries all day long but if I write a whole query in Notepad then execute it it's probably going to have some minor error in it somewhere too.
Start from the ground up. You're trying to get a list of forms the user has access to, so lets start with the forms_access table. So what's the most basic starting point? How about:
SELECT fa.role_id, fa.form_id
FROM forms_access fa
Ok, thats overly simplified but if that ran at least we know we're connected to the database.
So we can easily tell which form_ids each role has access to. Now we know our linking table to users is user_roles, so let's add that in:
SELECT ur.user_id, fa.form_id, fa.role_id
FROM forms_access fa
INNER JOIN user_roles ur ON fa.role_id = ur.role_id
So we've joined forms_access to user_roles on the foreign key role_id. Now we can see for every user_id, which role_id they have and which form_ids they can access.
So we're pretty much there, we just need the information from the forms table, so lets JOIN to that too:
SELECT ur.user_id, f.form_name, f.form_desc, fa.form_id, fa.role_id
FROM forms_access fa
INNER JOIN user_roles ur ON ur.role_id = fa.role_id
INNER JOIN forms f ON f.form_id = ur.form_id
Great! Now we have a list of each form_name/form_desc that each user_id can access.
Try the above step by step, if you skip to the end there could well be an error since I have not tested the code, and I don't know for sure that your table definitions match the question. If you do it step by step you only need to check the most recently added line to find the error.
I have just noticed in the question that you also need users.status = 'A', so in the same way as above you'll need to join to the users table on an appropriate foreign key, give it a go.
Now, once you've done all that you need to filter the results to a specific user_id - notice up till this point we haven't bothered with the WHERE clause.
Now don't go adding some variant of WHERE user_id = '$user' right away because then you've introduced 2 potential errors. Instead try adding WHERE user_id = 0 (or some known user_id). Does the query run and the results look correct? Great, now finally try adding in your php variable.
I'm having a small problem making a query in MySQL.
I have the following tables:
member;
group;
member_has_group (this one has the columns id_group referes to the group id and id_member referes to member id)
I'm trying to make a query that gives me the members from a selected group. Can you help me?
I'm not familiar with join tables, but for the search i made i think thats probably one of the solutions.
Thanks in advance.
Elkas
If you know the group id
select member.* from member m
inner join member_has_group mg on m.id = mg.id_member
where mg.id_group = [x]
If you only know the group name
select member.* from member m
inner join member_has_group mg on m.id = mg.id_member
inner join group g on g.id = mg.id_group
where g.name = 'group name'
This is trival in SQL :
SELECT m.id_member, m.name
FROM member AS m
INNER JOIN member_has_group AS h ON (m.id_member=h.id_member)
WHERE (h.id_group=#my_id_group)
#my_id_group is the group id you have to give.
Yep, you need a join here.
SELECT *
FROM `member`
JOIN `group` ON member.id = group.id
JOIN `member_has_group` ON group.id = member_has_group.id
Depending on the information in your tables, you may not need the third table at all.You only need a connector table with you have a "many to many" relationship between then.
(Ignore the rest if you already know
about database normalization)
For example, if you had two tables, Authors and Books. Authors would contain fields such as Name, Publisher, Birthday, whatever is a property of the "author". Books would contain relevant "book" information. This is a "one-to-many" relationship. An author may be linked (via a field such as author_id) to several books, but a book can only have one author. You would not need a third table here.
Building on that, say you had a third table for "Character Names". This would be a list of main character names used in any of the books in the "Books" table. One of the characters happens to be named John Steele. John has a whole series of books written about him. In the Books table, several of the books may list John Steele as a character. While in the characters table, John Steele could be listed in several books. This is "many-to-many". You need a third table here. It would only have two fields. A book_id and character_id, one entry for each book that John Steele appears in.
MySql Manual on DB Normalization