I have a problem in which I have a STUDENT table as
+-------------+-------------+-------------+-------------+---------------+
| roll_number | name | subject_one | subject_two | subject_three |
+-------------+-------------+-------------+-------------+---------------+
| 1 | Sheila | 32 | 48 | 64 |
| 2 | Rachel | 24 | 21 | 25 |
| 3 | Christopher | 55 | 12 | 10 |
+-------------+-------------+-------------+-------------+---------------+
I want the print the output as
+-------------+-------------+-------------+
| roll_number | name | total |
+-------------+-------------+-------------+
| 1 | Sheila | 144|
| 2 | Rachel | 70 |
| 3 | Christopher | 77 |
+-------------+-------------+-------------+
and select all student having marks greater than 75 ??
How can I achieve this using MYSQL ??
I think you just need the aggregate functions and using them is enough. I am not sure if it can help you or not.
SELECT roll_number , name , (subject_one + subject_two + subject_three) AS total FROM STUDENT HAVING total > 75 ;
Related
Let's say i have a user table like this :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 3 | Joseph | joseph410#mail.com | 21 |
| 4 | George | gge.48#mail.com | 28 |
| 5 | Joseph | jh.city89#mail.com | 24 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 8 | Joseph | psa.jos#mail.com | 34 |
| 9 | Joseph | joseph.la#mail.com | 28 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
In the actual, the database consists of more data and some of the data is duplicated, with more than two records. But the point is i want to get only the first and the second row of the duplicated rows that contains the name of "Joseph", How can i achieve this ? My code so far...
User::withTrashed()->groupBy('name')->havingRaw('count("name") >= 1')->get();
With that code the result will retrieve :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 3 | Joseph | joseph410#mail.com | 21 |
| 4 | George | gge.48#mail.com | 28 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
And i use this code to try to get the second duplicated row :
User::withTrashed()->groupBy('name')->havingRaw('count("name") >= 2')->get();
The result is still same as the mentioned above :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 3 | Joseph | joseph410#mail.com | 21 |
| 4 | George | gge.48#mail.com | 28 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
I want the result is to get record that have the id "5" with name "Joseph" like this :
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 1 | John | john.doe1#mail.com | 24 |
| 2 | Josh | josh99#mail.com | 29 |
| 4 | George | gge.48#mail.com | 28 |
| 5 | Joseph | jh.city89#mail.com | 24 |
| 6 | Kim | kimsd#mail.com | 32 |
| 7 | Bob | bob.s#mail.com | 38 |
| 10 | Jonathan | jonhan#mail.com | 22 |
+----+-----------+---------+------------+------+
But it seems only the first duplicate row is retrieved and i can't get the second duplicated row, can anybody give me suggestion ?
Let's start from your query
User::withTrashed()->groupBy('name')->havingRaw('count("name") >= 1')->get();
This will show all groups of rows whose count equals to 1 ore more. and this is the description of DISTINCT.
If you want to get only duplicate records you should get groups whose count is LARGER than 1.
The other thing to notice here is that a non-aggrigated column will be chosen randomly. because when you get a name and it's count, for example if you select name,count(name), email (email is not in the group by clause - not aggregated), and 4 rows have the same name. so you'll see:
+--------+-------------+-------+
| Name | Count(Name) | Email |
+--------+-------------+-------+
| Joseph | 4 | X |
+--------+-------------+-------+
what do you expect instead of X? which one of the 4 emails? actually, in SQLServer it's forbidden to select a non-aggrigated column and other databases will just give you a random one of the counted 3.
see this answer for more details it's explained very well: Do all columns in a SELECT list have to appear in a GROUP BY clause
So, we'll use having count(name) > 1 and select only the aggregated column name
DB::from('users')->select('name')->groupBy('name')->havingRaw('count("name") > 1')->get();
This should give you (didn't test it) this:
+--------+-------------+
| name | Count(name) |
+--------+-------------+
| Joseph | 4 |
+--------+-------------+
This will give you all names who have 2 or more instances. you can determine the number of duplicates in the having clause. for example having count(name) = 3 will give you all names which have exactly 3 duplicates.
So how to get the second duplicate? I have a question for that:
What is the first (original) duplicate? is it the one with the oldest created_at or the oldest updated_at ? or maybe some other condition?. because of that you should make another query with order by clause to give you the duplicates in the order most convenient to you. for example:
select * from `users` where `name` in (select `name` from users group by `name` having count(`name`) > 1) order by `id` asc
which will give:
+----+-----------+----------------------+------+
| ID | Name | Email | Age |
+----+-----------+----------------------+------+
| 3 | Joseph | joseph410#mail.com | 21 |
| 5 | Joseph | jh.city89#mail.com | 24 |
| 8 | Joseph | psa.jos#mail.com | 34 |
| 9 | Joseph | joseph.la#mail.com | 28 |
+----+-----------+---------+------------+------+
I have a table called transactions that looks like this:
transactions:
| id | PartNumber | Quantity |
I know that I can use the COUNT property in MySQL, which would give me the the duplicate part numbers in a new column called total_quantity:
SELECT COUNT(transactions.id) AS total_quantity
FROM transactions
GROUP BY transactions.PartNumber
However, now I already have an existing quantity column and want to compute a new count quantity taking into account the previous one as well and updating it in the existing quantity column
What's the most efficient way of doing this?
For example: I want to go from this:
transactions
| id | PartNumber | Quantity |
| 1 | 123 | 1 |
| 2 | 124 | 2 |
| 3 | 125 | 2 |
| 4 | 124 | 2 |
| 5 | 124 | 3 |
| 6 | 126 | 4 |
| 7 | 125 | 1 |
| 8 | 127 | 2 |
To this:
transactions
| id | PartNumber | Quantity |
| 1 | 123 | 1 |
| 2 | 124 | 7 |
| 3 | 125 | 3 |
| 4 | 126 | 4 |
| 5 | 127 | 2 |
You can use this sql request :
SELECT PartNumber, sum(Quantity) as 'SumQuantity' FROM transactions GROUP BY PartNumber
It will gives you sometings like this :
transactions
| PartNumber | SumQuantity |
| 123 | 1 |
| 124 | 7 |
| 125 | 3 |
| 126 | 4 |
| 127 | 2 |
You can find a code sample on SQL Fiddle
I have a table like this:
mysql> select * from studentscore;
+------------+-----------+-------+
| student_id | cource_id | score |
+------------+-----------+-------+
| 1 | 1 | 80 |
| 1 | 2 | 90 |
| 1 | 3 | 85 |
| 1 | 4 | 78 |
| 2 | 2 | 53 |
| 2 | 3 | 77 |
| 2 | 5 | 80 |
| 3 | 1 | 71 |
| 3 | 2 | 70 |
| 3 | 4 | 80 |
| 3 | 5 | 65 |
| 3 | 6 | 75 |
| 4 | 2 | 90 |
| 4 | 3 | 80 |
| 4 | 4 | 70 |
| 4 | 6 | 95 |
| 5 | 1 | 60 |
| 5 | 2 | 70 |
| 5 | 5 | 80 |
| 5 | 6 | 69 |
| 6 | 1 | 76 |
| 6 | 2 | 88 |
| 6 | 3 | 87 |
| 7 | 4 | 80 |
| 8 | 2 | 71 |
| 8 | 3 | 58 |
| 8 | 5 | 68 |
| 9 | 2 | 88 |
| 10 | 1 | 77 |
| 10 | 2 | 76 |
| 10 | 3 | 80 |
| 10 | 4 | 85 |
| 10 | 5 | 83 |
| 11 | 3 | 80 |
| 12 | 4 | 99 |
| 13 | 5 | 74 |
+------------+-----------+-------+
I want to show student_id and students' average scores that are higher than 80.
The output I want is like this:
+------------+-------------------+
| student_id | Average |
+------------+-------------------+
| 1 | 83.25 |
| 4 | 83.75 |
| 6 | 83.66666666666667 | // and how can I make this result shorter like 83.67?
| 7 | 80 |
| 9 | 88 |
| 10 | 80.2 |
| 11 | 80 |
| 12 | 99 |
+------------+-------------------+
I've tried the following codes
mysql> select student_id, avg(score) as average_score
-> from studentscore
-> group by student_id
-> where avg(score) >= 80;
and it gave me an syntax error.
I know by rules the where clause should go before the group by clause but I can't because the where clause depends on the result from the group by clause, and if I switch their position it will give me another error("Invalid use of group function").
Can some one tell me how to get the table I want?
use "having" instead of "where"
use having instead of where.
Here's the difference:
with where you can write a predicate that will be applied to each row
with having you can write a predicate that will applied to each group
and in your case, the 2nd is the only solution that can work.
select student_id, avg(score) as average_score
from studentscore
group by student_id
having avg(score) >= 80;
where applies a filter to your data before grouping has taken place, whereas having applies a filter post-grouping. round(,2) will format as you also ask:
select student_id, round(avg(score), 2) as average_score
from studentscore
group by student_id
having average_score >= 80;
I will better explain with tables:
table size
-----------------------------
id | type | size | cont_id |
-----------------------------
1 | GP | 30 | 21 |
2 | FR | 30 | 21 |
3 | UP | 40 | 21 |
4 | GT | 50 | 32 |
5 | UP | 40 | 32 |
-----------------------------
table buy
-------------------
cont_id | cus_nam |
-------------------
21 | xxx |
32 | zzz |
------------------
Now I want to combine two column into one and then do group_concat
This is what I want to do, output table should be like this:
------------------------------------
type | cont_id |
-----------------------------------
30GP ,30FR,40UP | 21 |
50GT , 40UP | 32 |
------------------------------------
You only need the first table. This is almost a basic aggregation:
select group_concat(size, type), cont_id
from size
group by cont_id;
I have a table like the one bellow:
+------+------+------+-------+
| pkey | name | exam | score |
+------+------+------+-------+
| 1 | Bob | Math| 75 |
| 2 | Bob | Eng | 77 |
| 3 | Bob | Phy | 78 |
| 4 | Sue | Math| 80 |
| 5 | Sue | Eng | 90 |
| 6 | Sue | Phy | 97 |
| 7 | Suzy | Math| 98 |
| 8 | Suzy | Eng | 99 |
| 9 | Suzy | Phy | 99 |
+------+------+------+-------+
And I want to make a query to pivot it into:
+------+------+------+-------+
| Name | Math | Phy | Eng |
+------+------+------+-------+
| Bob | 75 | 78 | 77 |
| Sue | 80 | 97 | 90 |
| Suzy| 90 | 99 | 99 |
+------+------+------+-------+
The problem is, the discipline of the exam can have like 500 different values and I can't define them all as they might change eventually and start having 600 different ones instead.
Is it possible to create a query that will read the value of the exam and create a new column to display the values of it?
Say for example they add Hist to the values of exam and say Suzy got a 100, it would then be like this:
+------+------+------+-------+-----+
| Name | Math | Phy | Eng | Hist|
+------+------+------+-------+-----+
| Bob | 75 | 78 | 77 | |
| Sue | 80 | 97 | 90 | |
| Suzy| 90 | 99 | 99 | 100 |
+------+------+------+-------+-----+
Thanks in advance
A SQL query has to have a well-defined set of columns. You can do what you want with a prepare statement and dynamic SQL.
Another approach would be to create a string of the possible values, such as Math:75, Phy78, Eng:77. If this works for you:
select name, group_concat(exam, ':', score separator ', ')
from table t
group by name;