I have 3 tables on my database: users, payment_methods and user_blocked_pm. The users table speaks for itself, the payment_methods stores all the payment methods the company uses, and the user_blocked_pm has the payment methods blocked for a specific user.
+------------------+
| users |
+-----+------------+
| id | user_name |
+-----+------------+
| 1 | John |
| 2 | Davis |
+-----+------------+
+-----------------------+
| payment_methods |
+-----+-----------------+
| id | payment_method |
+-----+-----------------+
| 1 | credit_card |
| 2 | cash |
+-----+-----------------+
+-----------------------------------+
| user_blocked_pm |
+-----+---------+-------------------+
| id | user_id | payment_method_id |
+-----+---------+-------------------+
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 2 | 2 |
+-----+---------+-------------------+
So, following the structure above, both payment_methods are blocked for the user John and cash is blocked for Davis.
Following this structure when there are multiple users and payment methods I'll have multiple records on user_blocked_pm because each user will be allowed to use only a few of the payment methods.
Is there a better way to work this relationship between the users and the user_blocked_pm so that the table doesn't get gigantic?
You do not need the id column in user_blocked_pm table because you going to select on user_id or pm_id
If the number of the allowed pm is less then the number of the not allowed, why not to make a user_allowed_pm table instead of user_blocked_pm
If you have a fixed number of pm for each user then you do not need a table just you create a column for every pm and you put the key of the pm (like a foreign key)
If you have a few user "types", then perhaps you can replace the user_blocked_pm with a user_type_blocked_pm. A "type" is a set of blocked/permitted payment methods. So the user_type_blocked_pm table is small -- has entries for the different types (users who can pay with cash only, users who can pay with credit and cash, etc. ) Then, you can add a column to the users table to indicate the user type.
Your method is fine, and the other ideas so far suggested are also fine. If the number of payment types is small (not more than 7, say - and certainly less than 64!), and finite, then you might also consider a bitwise method, where 1 = credit_card, 2 = cash, and 3 = both. I do this for days of the week, which are unlikely to ever be more than 7.
Related
I am working on a simple social app and have a user_friend table which has both the user_id and friend_id as its composite keys. In the front end, the current user can look at other people's profiles and then click on add friend button which updates the user_friend table. For example, user with id 100 can view user with id 9's and 15's profiles and click on add button and then the user_friend table gets updated as
user_id: 100, friend_id 9
and
user_id: 100, friend_id 15
What is the best approach to handling such request? I was thinking creating a new table called request_table which has requester column which has the id for the user, accepter column which has the id for the friend and status column with accepted and pending. So, when requester clicks add friend button, the status gets updated to accepted which then updates the user_friend table to to reflect the change (by adding a new row user_id: 9, friend_id 100 in the above example).
Please advice if there are cleaner or better ways to do this.
I would make it much simpler than you are thinking .. Your current table looks like:
+--------------------------------+
| user_id | friend_id |
+--------------+-=---------------+
| 100 | 15 |
+--------------+-----------------+
| 100 | 9 |
+--------------+-----------------+
Add two columns .. requested and accepted:
+--------------------------------+-----------------+----------------+
| user_id | friend_id | requested | accepted |
+--------------+-=---------------+-----------------+----------------+
| 100 | 15 | 1 | 0 |
+--------------+-----------------+-----------------+----------------+
| 100 | 9 | 1 | 1 |
+--------------+-----------------+-----------------+----------------+
Although one could ASSUME that if the entry is in the table requested will always be 1 -- So really you only need to add the accepted column .. But you get the basic idea/principle.
NOTE if you need more statuses than just "accepted" like -- Say "blocked" or "suspended" etc etc you can create a third table and use the in a relational way.
+-----------------------------------------------------------------+
| user_firends (uf_id for indexing FASTER) |
+--------------------------------+-----------------+--------------+
| uf_id | user_id | friend_id | status |
+--------------+-=---------------+-----------------+--------------+
| 1 | 100 | 9 | 1 |
+--------------+-----------------+-----------------+--------------+
| 2 | 100 | 15 | 2 |
+--------------+-----------------+-----------------+--------------+
+---------------------------------------+
| statuses_table |
+------------------+--------------------+
| status_id | status |
+------------------+--------------------+
| 1 | requested |
+------------------+--------------------+
| 2 | accepted |
+------------------+--------------------+
| 3 | rejected |
+------------------+--------------------+
| 4 | blocked |
+------------------+--------------------+
many (users) to many (friends) with a users_friends "pivot" table AND
many (friends) to single (staus) with a direct insert of status in the column
I am creating a web app that lets N number of users to enter receipt data.
A set of scanned receipts is given to users, but no more than 2 users should work on the same receipt.
i.e. User A and User B can work on receipt-1, but User C can not work on it(Another receipt, say receipt-2, should be assigned to the User C).
The table structure I am using looks similar to the following.
[User-Receipt Table]
+------------+--------------+
| user_id | receipt_id |
+------------+--------------+
| 000000001 | R0000000000 |
| 000000001 | R0000000001 |
| 000000001 | R0000000002 |
| 000000002 | R0000000000 |
| 000000002 | R0000000001 |
+------------+--------------+
[Receipt Table]
+-------------+--------+
| receipt_id | status |
+-------------+--------+
| R0000000000 | 0 |
| R0000000001 | 1 |
| R0000000002 | 0 |
| R0000000003 | 2 |
+-------------+--------+
★status 0:not assigned 1:assigned to a user 2: assigned to 2 users
select receipts from the receipt table whose status is not equal to '2'
insert the receipts fetched from the step 1 along with a user to whom receipts are assigned.
update the receipt status(0->1 or 1->2)
This is how I plan to achieve the above requirement.
The problem with this approach is that there could be a chance that the select(step1) is executed right before the update(step3) is executed.
If this happens, the receipts with status 2 might be fetched and assigned to another user, which does not meet the requirement.
How can I make sure that this does not happen?
For all purposes, use transactions :
START TRANSACTION
your SQL commands
COMMIT
Transactions either let all your statements executed or not executed at all and performs implicitly a lock on the updated row which is more efficient than the second approach
You can also do it using LOCK TABLE
I have a MySQL database that has a member table where there are multiple membership levels (e.g., Basic, Premium) of which a member can have one, and the membership level can change over time. I am working on constructing a query to give a count of the members of each type at any time, so the membership type of each member may be different than it is currently. To do this, I have a few additional tables.
types - Gives id associated with each membership type and its string
timeunits - Gives id associated with each time unit and its string
oldtypes - Gives the old membership type for a member and the time at which it was changed from that type
I know if I want to get a count of the members of each type currently, I can use:
SELECT types.type_desc, COUNT(*) FROM member INNER JOIN types ON member.type = types.type_id GROUP BY types.type_id;
What I'm not sure about is how to get the appropriate values from the oldtypes table given a time unit and use those with the member table to get a snapshot of the members and their memberships at any time. So if I were to get the memberships at timeunit = 2, I would see as a result:
| member_id | name | type |
|-----------|---------|------|
| 1 | Alice | 1 |
| 2 | Bob | 2 |
| 3 | Charlie | 1 |
| 4 | Daisy | 2 |
| 5 | Evan | 1 |
| 6 | Frank | 1 |
| 7 | Gloria | 2 |
| 8 | Henry | 2 |
SQL Fiddle
EDIT: The oldtypes table is constructed such that it gives the membership a member had prior to the listed time, at which point it was changed. So a row reading 4,1,2 indicates that member 4 changed from membership 1 at time 2.
I have a table of users where 1 column stores user's "roles".
We can assign multiple roles to particular user.
Then I want to store role IDs in the "roles" column.
But how can I store multiple values into a single column to save memory in a way that is easy to use? For example, storing using a comma-delimited field is not easy and uses memory.
Any ideas?
If a user can have multiple roles, it is probably better to have a user_role table that stores this information. It is normalised, and will be much easier to query.
A table like:
user_id | role
--------+-----------------
1 | Admin
2 | User
2 | Admin
3 | User
3 | Author
Will allow you to query for all users with a particular role, such as SELECT user_id, user.name FROM user_role JOIN user WHERE role='Admin' rather than having to use string parsing to get details out of a column.
Amongst other things this will be faster, as you can index the columns properly and will take marginally more space than any solution that puts multiple values into a single column - which is antithetical to what relational databases are designed for.
The reason this shouldn't be stored is that it is inefficient, for the reason DCoder states on the comment to this answer. To check if a user has a role, every row of the user table will need to be scanned, and then the "roles" column will have to be scanned using string matching - regardless of how this action is exposed, the RMDBS will need to perform string operations to parse the content. These are very expensive operations, and not at all good database design.
If you need to have a single column, I would strongly suggest that you no longer have a technical problem, but a people management one. Adding additional tables to an existing database that is under development, should not be difficult. If this isn't something you are authorised to do, explain to why the extra table is needed to the right person - because munging multiple values into a single column is a bad, bad idea.
You can also use bitwise logic with MySQL. role_id must be in BASE 2 (0, 1, 2, 4, 8, 16, 32...)
role_id | label
--------+-----------------
1 | Admin
2 | User
4 | Author
user_id | name | role
--------+-----------------
1 | John | 1
2 | Steve | 3
3 | Jack | 6
Bitwise logic allows you to select all user roles
SELECT * FROM users WHERE role & 1
-- returns all Admin users
SELECT * FROM users WHERE role & 5
-- returns all users who are admin or Author because 5 = 1 + 4
SELECT * FROM users WHERE role & 6
-- returns all users who are User or Author because 6 = 2 + 4
From your question what I got,
Suppose, you have to table. one is "meal" table and another one is "combo_meal" table. Now I think you want to store multiple meal_id inside one combo_meal_id without separating coma[,]. And you said that it'll make your DB to more standard.
If I not getting wrong from your question then please read carefully my suggestion bellow. It may be help you.
First think is your concept is right. Definitely it'll give you more standard DB.
For this you have to create one more table [ example table: combo_meal_relation ] for referencing those two table data. May be one visible example will clear it.
meal table
+------+--------+-----------+---------+
| id | name | serving | price |
+------+--------+-----------+---------+
| 1 | soup1 | 2 person | 12.50 |
+------+--------+-----------+---------+
| 2 | soup2 | 2 person | 15.50 |
+------+--------+-----------+---------+
| 3 | soup3 | 2 person | 23.00 |
+------+--------+-----------+---------+
| 4 | drink1 | 2 person | 4.50 |
+------+--------+-----------+---------+
| 5 | drink2 | 2 person | 3.50 |
+------+--------+-----------+---------+
| 6 | drink3 | 2 person | 5.50 |
+------+--------+-----------+---------+
| 7 | frui1 | 2 person | 3.00 |
+------+--------+-----------+---------+
| 8 | fruit2 | 2 person | 3.50 |
+------+--------+-----------+---------+
| 9 | fruit3 | 2 person | 4.50 |
+------+--------+-----------+---------+
combo_meal table
+------+--------------+-----------+
| id | combo_name | serving |
+------+--------------+-----------+
| 1 | combo1 | 2 person |
+------+--------------+-----------+
| 2 | combo2 | 2 person |
+------+--------------+-----------+
| 4 | combo3 | 2 person |
+------+--------------+-----------+
combo_meal_relation
+------+--------------+-----------+
| id | combo_meal_id| meal_id |
+------+--------------+-----------+
| 1 | 1 | 1 |
+------+--------------+-----------+
| 2 | 1 | 2 |
+------+--------------+-----------+
| 3 | 1 | 3 |
+------+--------------+-----------+
| 4 | 2 | 4 |
+------+--------------+-----------+
| 5 | 2 | 2 |
+------+--------------+-----------+
| 6 | 2 | 7 |
+------+--------------+-----------+
When you search inside table then it'll generate faster result.
search query:
SELECT m.*
FROM combo_meal cm
JOIN meal m
ON m.id = cm.meal_id
WHERE cm.combo_id = 1
Hopefully you understand :)
You could do something like this
INSERT INTO table (id, roles) VALUES ('', '2,3,4');
Then to find it use FIND_IN_SET
As you might already know, storing multiple values in a cell goes against 1NF form. If youre fine with that, using a json column type is a great way and has good methods to query properly.
SELECT * FROM table_name
WHERE JSON_CONTAINS(column_name, '"value 2"', '$')
Will return any entry with json data like
[
"value",
"value 2",
"value 3"
]
Youre using json, so remember, youre query performance will go down the drain.
I am quite new to MySQL, I know most of the basic functions and how to send queries etc. However, I am trying to learn about structuring it for optimal searches for user information and wanted to get some ideas.
Right now I just have one table (for functionality purposes and testing) called user_info which holds the users information and another table that stores photos linked to the user. Ideally id like most of this information to be as quickly as accessible as possible
In creating a database which is primarily used to store and retrieve user information (name, age, phone, messages, etc.) would it be a good idea to create a NEW TABLE for each new user that stores all the information so the one table user_info does not become bogged down by multiple queries, locking, etc. So for example user john smith would have his very own table in the database holding all his information including photos, messages etc.
OR
is it better to have just a few tables such as user_info, user_photos, user_messages,etc. and accessing data in this manner.
I am not concerned about redundancy in the tables such as the users email address being repeated multiple times.
The latter is the best way. You declare one table for users, and several columns with the data you want.
Now if you want users to have photos, you'd require a new table with photos and a Foreign Key attribute that links to the user table's Primary Key.
You should definitely NOT create a new table for each user. Create one table for user_info, one for photos if each user can have many photos. A messages table would probably contain two user_id columns (user_to, user_from) and a message column. Try to normalize the data as much as possible.
Users
====
id
email
etc
Photos
====
id
user_id
meta_data
etc
Messages
====
id
user_id_to
user_id_from
message
timestamp
etc
I agree with both the answers supplied here, but one thing they haven't mentioned yet is lookup tables.
Going with the general examples here consider this: you have a users table, and a photos table. Now you want to introduce a featre on your site that allows users to "Favorite" photos from other users.
Rather than making a new table called "Favorites" and adding in all your data about the image (fiel location, metadata, score/whatever) all over again, have a table that effectively sits BETWEEN the other two.
+-----------------------+ +-------------------------------------+
| ++ users | | ++ photos |
| userID | email | name | | photoID | ownerID | fileLo | etc... |
+--------+-------+------| +---------+---------+--------+--------+
| 1 | .... | Tom | | 35 | 1 | ..... | .......|
| 2 | .... | Rob | | 36 | 2 | ..... | .......|
| 3 | .... | Dan | | 37 | 1 | ..... | .......|
+--------+-------+------+ | 43 | 3 | ..... | .......|
| 48 | 2 | ..... | .......|
| 49 | 3 | ..... | .......|
| 53 | 2 | ..... | .......|
+---------+---------+--------+--------+
+------------------+
| ++ Favs |
| userID | photoID |
+--------+---------+
| 1 | 37 |
| 1 | 48 |
| 2 | 37 |
+--------+---------+
With this approach, you link the data you have cleanly, efficiently and without too much data replication.