I have a MySQL db set up like so,
user_table table
user_ID PK
username
password
email
level
location
game_items table
game_item_is PK
item_name
user_inventory table
user_inventory_id PK
user_id FK
game_item_id FK
quantity
This is a db for a game i am building and i am trying to code an sql query to get the following data out of the db:
Level
Location
A list of game items the user has associated to their user_id
The data i already have is the user_id and username.
So how would i go about creating this sql statement? would i use joins? if so where?
I want to get every game_item the user has associated with their account so would this include * anywhere?
Thanks
Ok so after a while playing with the sql on phpmyadmin i got the result i wanted, if anyone would like to know here is the code:
SELECT ut.username, ut.level, ut.location, ui.quantity, ui.game_item_id
FROM user_table ut, user_inventory ui
WHERE ut.user_id = ui.user_id
AND ut.user_id =1
If I understand your question correctly, just select the level and location in one query and the inventory items in another
SELECT level, location FROM user_table WHERE id = ..
SELECT * FROM user_inventory WHERE id = ..
Related
i am creating a restaurant review website. in my review table i have a foreign key called user_id and idk how to use it to display the username which is in the user table
my user table
my review table
so my question is how do i display the username from this? what mysql statement do i have to write. I am lost on what to do
Assuming you want to try and get the review text along with the user name from the corresponding user you can use a join to combine the info for example:
SELECT u.username, r.review_text
FROM reviews r
LEFT JOIN users u
ON (u.user_id = r.user_id)
I assumed the users table is called users and reviews table is called reviews but update those as necessary each is "aliased" as u and r respectively and then tables are joined
If the relationship between the two tables is mapped out correctly you should be able to run a query to fetch the name of each user. Try to avoid any N+1 query though
I have a table called followers and I want to be able to find the current users followers, display that list, and then compare those values against another user ID to see if they are following them or not from that same table
This is the table I'm using currently to get the list of followers for a specific user:
followers
-------
followId - primary key, the unique id for the follow relationship
userId - the user that is following someone
orgId - that someone that the user is following
I tried using a union query but I wouldn't want to due to performance reasons (table may contain high volume of records) and because it isn't scalable (I think)?
The expected output should be the list of orgId's for which the user(the user I am checking against) is following, and another column that shows whether my user(my userId that I provide) is following that orgId value (i.e a following column).
Hmmm, if I understand correctly, you have two users and you want to know which orgs followed by the first are also followed by the second:
select f.orgid,
(exists (select 1
from followers f2
where f2.userId = $seconduserid and
f2.orgid = f.orgid
)
) as seconduserflag
from followers f
where f.userId = $firstuserid
I have a cross-reference table that supplies the many-to-many relationship between users and user group tables. It contains two relevant columns: group_id and user_id (surprise, surprise!). When a user wants to create a new group, I want to first check if that set of users already exists as a group.
Essentially I would define the problem as "Given a set of user ids, find any set of rows that match the set of user ids and all share the same group id".
Edit:
I'm looking for the exact set of users, not interesting in seeing in the resultset groups that include those users in addition to other users.
Sample Data
I have the hunch that a subquery is the way to go, but I can't figure out how to arrange it. Any help would be greatly appreciated!
Is this what you want?
select groupid
from usergroups ug
where userid in ($user1, $user2, . . . , $usern)
group by groupid
having count(*) = <n>;
This returns all groups that have the supplied list of users.
If you want the exact set, then:
select groupid
from usergroups ug
group by groupid
having count(*) = sum( userid in ($user1, $user2, . . . , $usern) );
This assumes that groups don't have the same user twice (it is not hard to adjust for that, but the condition becomes more complicated).
I have two tables gcm_users and vechicle_master with me.
gcm_users has session id named ID which is generated automatically*(A_I Primary Key)* when user registers.I use this session id in my query to identify the user at time of log in.
requirement - i want to show all the vehicle details from vehicle_master table which are related with the user from the gcm_user table.
NOTE:
when a user logs in, he should only see his own vehicle details.
Try using JOIN you can do like, put your user_id in place of 1
SELECT a.*
FROM vehicle_master a
JOIN gcm_users b
ON a.registration_no = b.registration_no
WHERE user_id = 1
My question is similar (but at the same time completely different) than this question:
Contacts Database
The question is simple: How can I create a Contacts database table which stores a user id and contact id without duplicating keys.
For example, if I have a table called Contacts, it would have a column user_id, and a column contact_id.
Once I do that, it should be as simple as inserting the user and the added contact. Once that is done though, how do I select all of a user's contacts? Also, how do I narrow down the contact entry enough to delete it if need be?
I ended up just creating a table with two foreign keys and then selecting them based on either of the fields.
For example (pseudo code--no specific language, just english):
Table Contact:
user = ForeignKey(from user table)
contact = ForeignKey(from user table)
Then whenever I need something from them, I'll check if the user field contains what I want and then I'll check if the contact field has what I want. This way I don't have to repeat records and I can still find what I need.
Thanks for your answers.
Similar to the question in the link. You would have 3 tables.
Table 1
User_ID
Name
PK(User_ID)
Table 2
Contact_id
Address
Phone_Number
etc...
PK(Contact_id)
Table 3
User_ID
Contact_id
PK(User_ID, Contact_id)
Here you would have ContactID in table 2 as an autoinc column.
Also, when inserting in Table 3, MySQL would throw an error if there is a duplicate.
To select all of a users contacts, use:
SELECT *
FROM Table_2 join Table_3
ON Table_2.Contact_id = Table_3.contact_id
WHERE Table2.User_id = <userid>
Or if you need it for a particular name, then
SELECT *
FROM Table_1 JOIN Table_2
ON Table_1.User_id = Table_2.User_id
JOIN Table_3
ON Table_2.Contact_id = Table_3.contact_id
WHERE Table1.name = <user name>
there are two questions.
" how do I select all of a user's contacts?"
So you have a table tbl_contacts(user_id, contact_id) both them are your primary key, so you won't get duplicated data.
I you want to list all contacts for user_id = ?
SELECT *
FROM tbl_contacts
WHERE user_id = ?
You might want to clarify your second question "Also, how do I narrow down the contact entry enough to delete it if need be?"
You probably have some other properties belong to the user's contact and you will need to use those properties to search for.(eg.: contact_name or contact_number) and when you have 1 record as a result of a query you can -> DELETE FROM tbl_contact WHERE contact_id = ?
If this is not the answer you wanted please clarify your question.