Hello I am currently learning programming and I am working on a project of php and mysql, but I have a problem.
What I am doing is I have a table called marks and every time people add a mark to a student, they add a column to the table, the table looks like this:
|------------------|
| subject | marks |
|------------------|
| math | 16 |
| english | 18 |
| history | 15 |
| math | 14 |
| english | 20 |
|------------------|
But I want to change it like this when I treat it:
|-------------------------|
| math | 16 | 14 |
| english | 18 | 20 |
| history | 15 | |
|-------------------------|
How can I do this with mysql's query, or php if needed?
Well my final goal is to make html table with this but I already know how to do it.
I am sorry if it looked simple, but I am really a beginner at databases and programming and I apologize if the title confuses you guys.
You can try
SELECT subject, GROUP_CONCAT(marks ORDER BY marks) marks
FROM table
GROUP BY subject
ORDER BY subject
It will give you two columns, one with a comma-separated list of subjects.
english 18, 20
history 15
math 14, 16
Related
Hello :) I am fairly new to using INNER JOIN and still trying to comprehend it's logic which I think I am sort of beginning to understand. After being across a few different articles on the topic I have generated a query for finding duplicates in my table of phone numbers.
My table structure is as such:
+---------+-------+
| PhoneID | Phone |
+---------+-------+
Very simple. I created this query:
SELECT A.PhoneID, B.PhoneID FROM T_Phone A
INNER JOIN T_Phone B
ON A.Phone = B.Phone AND A.PhoneID < B.PhoneID
Which returns the ID of a phone that matches another one. I don't know how to word that properly so here is an example output:
+---------+---------+
| PhoneID | PhoneID |
+---------+---------+
| 17919 | 17969 |
| 17919 | 22206 |
| 17919 | 23837 |
| 17920 | 17970 |
| 17920 | 22203 |
| 17920 | 23834 |
| 17921 | 17971 |
| 17921 | 22225 |
| 17921 | 22465 |
| 17921 | 24011 |
| 17921 | 24047 |
| 17922 | 17972 |
| 17922 | 22198 |
| 17922 | 23879 |
| 17923 | 17973 |
| 17923 | 22199 |
| 17923 | 23880 |
+---------+---------+
You can note that on the left there is repeating IDs, the phone number that matches will be on the right (These are just the IDs of said numbers). what I am trying to accomplish, is to actually change a join table relative to the ID on the right. The join table structure is as such:
+----------+-----------+
| T_JoinID | T_PhoneID |
+----------+-----------+
Where T_JoinID is a larger object with a collection of those T_PhoneIDs, hence the join table. What I want to do is take a row from the original match query, and find the right side PhoneID in the join table, then update that item in the Join to be equal to the left side PhoneID. Repeating this for each row.
It's sort of a way to save space and get rid of matching numbers, I can just point the matching ones to the original and use that as a reference when I need to retrieve it.
After that I need to actually delete the original numbers that I reset the reference for but... This seems like a job for 2 or 3 different queries.
EDIT:
Sorry I know I didn't include enough detail. Here is some additional info:
My exact table structure is not the same as here but I am only using the columns that I listed so I didn't consider the fact that any of the others would matter. Most of the tables have a unique ID that is auto incremented. The phone table has carrier, type, ect columns. The additional columns I felt were irrelevant to include, but if there is a solution that includes the auto incremented ID of each table, let me know :) Anyway, I sort of found a solution, using multiple queries though I am still interested to learn and apply knowledge based on this question. So I have a that join table that I mentioned. It might look something like this for the expected results. There is a before and after table in one sorry for poor formatting.
+--------------------+---------+----------+---------+
| Join Table Results | | | |
+--------------------+---------+----------+---------+
| Before | | After | |
| Join | Table | Join | Table |
| PersonID | PhoneID | PersonID | PhoneID |
| 1 | 1 | 1 | 1 |
| 1 | 2 | 1 | 2 |
| 1 | 3 | 1 | 3 |
| 2 | 4 | 2 | 1 |
| 2 | 5 | 2 | 5 |
| 2 | 6 | 2 | 6 |
| 3 | 7 | 3 | 5 |
| 3 | 8 | 3 | 5 |
| 3 | 9 | 3 | 5 |
| 3 | 10 | 3 | 8 |
| 3 | 11 | 3 | 9 |
+--------------------+---------+----------+---------+
So you can see that in the before columns, 7, 8, and 9 would all be duplicate phone numbers in the PhoneID - PhoneID relationship table I posted originally. After the query I wanted to retrieve the duplicates using the PhoneID - PhoneID comparison and take the ones that match, to change the join table in a way that I have shown directly above. So 7, 8, 9 all turn to 5. Because 5 is the original number, and 7, 8, 9 coincidentally were duplicates of 5. So I am basically pointing all of them to 5, and then deleting what would have been 7, 8, 9 in my Phone table since they all have a new relationship to 5. Is this making sense? xD It sounds outrageous typing it out.
End Edit
How can I improve my query to accomplish this task? Is it possible using an UPDATE statement? I was also considering just looping through this output and updating each row individually but I had a hope to just use a single query to save time and code. Typing it out makes me feel a tad obnoxious but I had hope there was a solution out there!
Thank you to anyone in advance for taking your time to help me out :) I really appreciate it. If it sounds outlandish, let me know I will just use multiple queries.
I need to design a db model for a backend module where user can translate page content into multiple languages. The things that will be translated are basic words, phrases, link names, titles, field names, field values. They should also be grouped so i can find them by group name. For example if there is a select field on page with different colors as options then i should be able to select all of them by group name.
So here is what i have at the moment:
lang
+----+---------+
| id | name |
+----+---------+
| 1 | english |
| 2 | german |
+----+---------+
lang_entity
+----+------------+-------------+-------+-------+
| id | module | group | name | order |
+----+------------+-------------+-------+-------+
| 1 | general | | hello | 0 |
| 2 | accounting | colorSelect | one | 1 |
| 3 | accounting | colorSelect | two | 2 |
| 4 | accounting | colorSelect | three | 3 |
+----+------------+-------------+-------+-------+
lang_entity_translation
+----+---------+----------------+-------------+
| id | lang_id | lang_entity_id | translation |
+----+---------+----------------+-------------+
| 1 | 1 | 1 | Hello |
| 2 | 2 | 1 | Guten tag |
| 3 | 1 | 2 | One |
| 4 | 2 | 2 | Ein |
| 5 | 1 | 3 | Two |
| 6 | 2 | 3 | Zwei |
| 7 | 1 | 4 | Three |
| 8 | 2 | 4 | Drei |
+----+---------+----------------+-------------+
So lang table holds different languages.
Table lang_entity has entities that can be translated for different languages.
Module row is just to group them by page modules in the backend translating module. Also this gives me possiblity to have entities with same name for different modules.
Group as mentioned is needed for selects and maybe some other places where multiple values are going to be used. This also gives me an option to allow user to add and order entities in one group.
And table lang_entity_translation holds the translations for each entity in each language.
So my question is are visible flaws in this kind of a design? Would you reccomend something different?
Also a bonus question: I really dont like the lang_entity table name, do you have a better idea of a table name that would hold all the words/phrases that are translated? :)
Edit: similar, but not a duplicate. The linked question is about translating dynamic products and having a seperate table for each translated type. Im talking about translating whole page content, including groups in a single table.
I don't understand the order column of lang_entity, but then I probably don't need to.
The setup looks sane, but make sure you add foreign key constraints from lang_entity_translation to language and lang_entity.
As for naming, I would call the table phrase or translatable.
We had similar situation. This was 7 years before.
We had different column for different language. Like for name we had
Name_Eng,Name_Ger,Name_Spa .We had 7-10 language.
We had common id for name for all language.
Based on the Language selection from UI we passed the language code to Back end In the Stored proc it was appended to the column Name
Example, we will be passing "Eng" if English is selected and we form the column name as Name_Eng and fetch the data. we were using dynamic query.
Hello I am facing hard time trying to realized this task. The problem is that I am not sure in which way this have to be proceeded and couldn't find tutorials or information about realizing this type of task.
The question is I have 2 tables and one connecting table between the two of them. With regular query usually what is displayed is the table header which is known value and them then data. In My case I have to display the table horizontally and vertically since the header value is unknown value.
Here is example of the DB
Clients:
+--------+------ +
| ID | client|
+--------+------ +
| 1 | Sony |
| 2 | Dell |
+--------+------ +
Users:
+--------+---------+------------+
| ID | name | department |
+--------+--------+-------------+
| 1 | John | 1|
| 2 | Dave | 2|
| 3 | Michael| 1|
| 4 | Rich | 3|
+--------+--------+-------------+
Time:
+--------+------+---------------------+------------+
| ID | user | clientid | time | date |
+--------+------+---------------------+------------+
| 1 | 1 | 1 | 01:00:00 | 2017-01-02 |
| 2 | 2 | 2 | 02:00:00 | 2017-01-02 |
| 3 | 1 | 2 | 04:00:00 | 2017-02-02 | -> Result Not Selected since date is different
| 4 | 4 | 1 | 02:00:00 | 2017-01-02 |
| 5 | 1 | 1 | 02:00:00 | 2017-01-02 |
+--------+------+---------------------+------------+
Result Table
+------------+--------+-----------+---------+----------+
| Client | John | Michael | Rich | Dave |
+------------+--------+-----------+---------+----------+
| Sony |3:00:00 | 0 | 2:00:00 | 0 |
+------------+--------+-----------+---------+----------+
| Dell | 0 | 0 | 0 | 2:00:00 |
+------------+--------+-----------+---------+----------+
First table Clients Contains information about clients.
Second table Users Contains information about users
Third Table Time contains rows of time for each users dedicated to different clients from the clients table.
So my goal is to make a SQL Query which will show the Result table. In other words it will select sum of hours which every user have completed for certain client. The number of clients and users is unknown. So first thing that have to be done is Select all users, no matter if they have hours completed or not. After that have to select each client and the sum of hours for each client which was realized for individual user.
The problem is I don't know how to approach this situation. Do I have first to make one query slecting all users then foreach them in the table header and then realize second query selecting the hours and foreaching the body conent, or this can be made with single query which will render the whole table.
The filters for select command are:
WHERE MONTH(`date`) = '$month'
AND YEAR(`date`) ='$year'
AND u.department = '$department'
Selecting single row for tume SUM is:
(SELECT SUM( TIME_TO_SEC( `time` ) ) FROM Time tm
WHERE tm.clientid = c.id AND MONTH(`date`) = '$month' AND YEAR(`date`) ='$year'
This is the query to select the times for a user , here by my logic this might be transformed with GROUP BY c.id (client id), and the problem is that it have to contains another WHERE clause which will specify the USER which is unknown. If the users was known value was for example 5, there is no problem to make 5 subsequent for each user WHERE u.id = 1, 2, 3 etc.
So here are the 2 major problems how to display in same query The users header and them select the sum of hours for each client corresponding the user.
Check out the result table hope to make the things clear.
Any suggestion or answer which can come to resolve this situation will be very helpful.
Thank you!
I'm displaying a record set using Datatables pulling records from two tables.
Table A
sno | item_id | start_date | end_date | created_on |
===========================================================
10523563 | 2 | 2013-10-24 | 2013-10-27 | 2013-01-22 |
10535677 | 25 | 2013-11-18 | 2013-11-29 | 2013-01-22 |
10587723 | 11 | 2013-05-04 | 2013-05-24 | 2013-01-22 |
10598734 | 5 | 2013-06-14 | 2013-06-22 | 2013-01-22 |
Table B
id | item_name |
=====================================
2 | Timesheet testing |
25 | Vigour |
11 | Fabwash |
5 | Cruise |
Now since the number of records returned is going to turn into a big number in near future, I want the processing to be done serverside. I've successfully managed to achieve that but it came at a cost. I'm running into a problem while dealing with filters.
From the figure above, (1) is the column whose value will be in int (item_id), but using some small modifications inside the while loop of the mysql resource, I'm displaying the corresponding string using Table B.
Now if I use the filter (2), it is working fine since those values come from Table A
The Problem
When I try to filter from the field (3), if I enter a string value such as fab it says no record found. But if I enter an int such as 11 I get a single row which contains Fabwash as the item name.
So while filtering I'm required to use the direct value used in Table A and not its corresponding string value stored in Table B. I hope the point that I'm putting across is understandable because it is hard to explain it in words.
I'm clueless on how to solve the issue.
For a table with 100% reading (no writing), which structure is better and why?
[My table has many columns, but I've made an example here with 4 columns for simplicity]
Option 1: One table with multiple columns
ID | Length | Width | Height
-----------------------------------------
1 | 10 | 20 | 30
2 | 100 | 200 | 300
Option 2: Two tables; one storing column headers, and other storing values
Table 1:
ID | Object_ID | Attribute_ID | Attribute_Value
------------------------------------------
1 | 1 | 1 | 10
2 | 1 | 2 | 20
3 | 1 | 3 | 30
4 | 2 | 1 | 100
5 | 2 | 2 | 200
6 | 2 | 3 | 300
Table 2:
ID | Name
-------------------
1 | Length
2 | Width
3 | Height
Your second option is an under-optimized implementation of the EAV anti-pattern:
Entity-Attribute-Value Model
Why it's bad has already been argued to death on this site and elsewhere.
You'll get much better results from the first.
I will preface this by saying that I'm a relative novice to SQL and database tables; that, however, doesn't mean that I don't know my basics.
Unless your example is heavily oversimplified, you really should use the first example. Not only will it be faster and easier to query, but it simply makes more sense.
In this example, you don't need to split your tables at all; your 'Attribute IDs' are adequately represented by the table headers. Further, these values have no real meaning by themselves, so they really don't need to be in another table.
You would generally break out a new table and reference it as you have if you had another object, existing separately, relating to your object with a one-to-many relationship.
Here's an example (actually from my database on an O'Reilly server) using blog entries and comments on blog entries:
mysql> select * from blog_entries;
+----+--------------+-------------+---------------------+
| id | poster | post | timestamp |
+----+--------------+-------------+---------------------+
| 1 | lunchmeat317 | blah blah | 0000-00-00 00:00:00 |
| 2 | Yongho Shin | yadda yadda | 0000-00-00 00:00:00 |
+----+--------------+-------------+---------------------+
2 rows in set (0.00 sec)
mysql> select id, blog_id, poster, post, timestamp from blog_comments;
+----+---------+--------------+----------------+---------------------+
| id | blog_id | poster | post | timestamp |
+----+---------+--------------+----------------+---------------------+
| 1 | 1 | lunchmeat317 | humina humina | 0000-00-00 00:00:00 |
| 2 | 1 | Joe Blow | huh? | 0000-00-00 00:00:00 |
| 3 | 2 | lunchmeat317 | yakk yakk yakk | 0000-00-00 00:00:00 |
| 4 | 2 | Yongho Shin | lol | 0000-00-00 00:00:00 |
+----+---------+--------------+----------------+---------------------+
4 rows in set (0.00 sec)
mysql>
Think about it from a logical perspective; there's no reason to artificially inject complexity into this design when it doesn't need to be there. In your example, length, width, and height aren't really separate objects, and they're all related to the dimensions of the object you're describing in the table row. Further, length width and height only have one value at a given time.
I hope that made some sense - if I was a bit pedantic in my pedagogy, I apologize. However, if someone else stumbles on this question, hopefully this example will help them.
Good luck.
Edit: I just realized that your question was specifically about performance. That's a little more in-depth, perhaps based on the db engine that you use? Generally, though, I would imagine that querying a table without doing any joins would be slightly faster, considering that denormalization is a commonly-cited method of improving performance.