I have these sample course_numbers
cmsc 11
cmsc 2
cmsc 56
cmsc 21
cmsc 128
I use this query
SELECT * FROM subject ORDER BY LENGTH(`course_number`)
to natural sort the result
and it worked, but when i add these course_numbers
it 1
it 256
it 20
they kinda mess up.
What query should i use to order them like this
cmsc 2
cmsc 11
cmsc 21
cmsc 56
cmsc 128
it 1
it 11
it 20
it 100
it 256
I've searched and saw 'case' on their select statements but I do not know how to use them
You should consider splitting up the both parts of your course number, since "CMSC"/"IT" is one Part (even with variable length), and the real number is another part. If you store the number in a number column (int), you could easily correct them.
so it would be
SELECT concat(course_type, " ", course_subnumber) as course_number, ...
from subject
order by course_type, course_subnumber
As long as you have a bit luck, you could try with you structure the following:
SELECT * from subject
order by left(course_number, 2), length(course_number), course_number
then you get only in trouble if different course_types start with the same two letters.
Related
For example, let us consider this table:
In this image consists of rows of 8 where names like Mike,Glenn,Daryl,Shane and Patricia is included with their respective ages
Id
Name
Age
1
Mike
25
2
Glenn
19
3
Glenn
19
4
Daryl
56
5
Shane
30
6
Shane
30
7
Patricia
16
Now I want to insert the type of query that will show the names without repetitions like This, not like This
EDIT: I entered the data from first picture. The request is to list the names without duplicates, as shown in the second and third picture but I will not convert them to text.
DISTINCT specifies removal of duplicate rows from the result set.
SELECT DISTINCT Name
FROM tablename
see: use DISTINCT in SELECT
You can use GROUP BY to achieve it.
SELECT * FROM your_table
GROUP BY your_table.name
ORDER BY id
With the data you gave, the result from this query will be:
id
name
age
1
Mike
25
2
Glenn
19
4
Deryl
56
5
Shane
30
7
Patricia
16
I'm just stuck with this issue atm and I'm not 100% sure how to deal with it.
I have a table where I'm aggregating data on week
select week(create_date),count(*)
from user
where create_date > '2015-02-01'
and id_customer between 9 and 17
group by week(create_date);
the results that I'm getting have missing values in the count, as shown below
5 334
6 376
7 394
8 405
9 504
10 569
11 709
12 679
13 802
14 936
15 1081
16 559
21 1
24 9
25 22
26 1
32 3
34 1
35 1
For example here from 16 to 21 there a obviously 4 values missing I would like these values to be included and count to be 0. I want this because I want the weeks to be matching with other metrics as we are outputting them in an excel file for internal analysis.
Any help would be greatly appreciated.
The problem is that an sql query cannot really produce data that is not there at all.
You have 3 options:
If you have data for each week in your entire table for the period you are querying, then you can use a self join to get the missing weeks:
select week(t1.create_date), count(t2.id_customer)
from customer t1
left join customer t2 on t1.id_customer=t2.id_customer and t1.create_date=t2.create_date and t2.id_customer between 9 and 17
where t1.create_date > '2015-02-01'
group by week(t1.create_date)
If you have missing weeks from the customer table as whole, then create a helper table that contain week numbers from 1 or 0 (depending on mysql config) to 53 and do a left join to this helper table.
Use a stored procedure that loops through the results of your original query and inserts the missing data in the resultset using a temporary table and then returns the extended dataset as result.
The problem is that there is no data matching your criteria for the missing weeks. A solution will be to join from a table that has all week numbers. For example if you create a table weeknumbers with one field weeknumber containing all the numbers from 0 to 53 you can use something like this
select weeknumber,count(user.*)
from weeknumbers left join user on (weeknumbers.weeknumber=week(user.create_date)
and user.create_date > '2015-02-01'
and user.id_customer between 9 and 17)
group by weeknumber;
Additionaly you might want to limit the week numbers you do not want to see.
The other way is to do it in the application.
I have searched and found discussions and solutions to similar problems, but not quite or as complex as I'm trying to figure out.
I have an access table which consists of two columns Draw Number and Number Drawn as shown below. Draw Number is repeated 20 times, to correspond to the 20 numbers that are drawn in each particular draw.
I'm trying to figure a way to determine the most frequent occurring combination of numbers (5 numbers) for all of the draws in each of the 20 number sets. So for instance, 12341 occurs n x, 12342 occurs nx, 12343 occurs n x, etc.
I've created parameter queries which allow me to search for different number combinations from 2 to 10 numbers, and they work OK returning the number of occurrences of a combination of numbers that I input through a simple UI. But the goal is to figure out pragmatically what the optimum combination of numbers.
Hope this makes sense. And by the way, there are 36 million or so rows in the table. The para queries work quite well however; it takes just over a second to return results for each number added. So, query two numbers = 2 second wait, three numbers = 3 second wait, etc.
I've been thinking about a loop of some type but don't know how to get started? Processing time isn't an issue; can take a day if required!
This is written in VBA and has an assortment of queries, temp tables, etc to get the job done.
The text says Access, but the tags say MySql, which is it? – RBarryYoung 21 hours ago
This part confuses me: I'm trying to figure a way to determine the most frequent occurring combination of numbers (5 numbers) for all of the draws in each of the 20 number sets. So for instance, 12341 occurs n x, 12342 occurs nx, 12343 occurs n x, etc. – Newd 21 hours ago
^What do you mean five numbers? No where in your sample data do I see 12341. Please explain using the data you have, and give expected results using that data. – McAdam331 21 hours ago
drosberg - clarification:
thanks for the response. It is an Access application, but as a first-time poster Stackoverflow recommends tags?
By five numbers I mean the most frequently occurring group of five numbers (I used five as an example, could be groups of 2 to 10 numbers) which occur in each draw, where a draw consists of 20 drawn numbers from a total of 80 numbers. So the data that I posted was intended as an example. The sample provided only has 50, 51 in common. I can plug 50 and 51 into the parameter query and it will tell me that this combination occurs 60,000 times (or whatever), but perhaps 50 and 57 occurs 65,000 times.
If i was to do this manually, and assuming I'm looking for the most frequent 5 number combination I would enter the following in the parameter query: 1,2,3,4,1 group = 30,000 occurrences 1,2,3,4,2 group = 31,000 occurrences 1,2,3,4,3 group = 31,050 occurrences 1,2,3,4,4 group = 29,050 occurrences etc........... etc...........
but I would have to do this for every combination of 5 numbers that can be derived from the numbers 1 thru 80. I'm hoping to have program do the work!!
thanks
don
DRAW NUMBER NUMBER DRAWN
1 1
1 28
1 19
1 3
1 38
1 46
1 43
1 29
1 13
1 22
1 20
1 11
1 50
1 51
1 53
1 54
1 57
1 64
1 76
1 78
2 29
2 14
2 2
2 1
2 35
2 40
2 39
2 30
2 10
2 27
2 21
2 6
2 42
2 50
2 51
2 53
2 54
2 61
2 65
2 69
I wrote a post a while ago about generating permutations with and without repetition using Excel. Perhaps you can use it.
https://michiel.wordpress.com/2015/03/29/permutations-with-repetition-using-excel/
Here's how it works. I am using strings, but you can easily modify that for numbers (since you say you need 5).
You can use the MID function to grab a single char from a string, and generate permutations from it.
=MID(Pattern,MOD([N]/[P],Length)+1,1)
N revers to the column N
P refers to the horizontal row (1,4,16). You can generate these with a formula like =4^.
After putting in the code, you can make a list of all permutations in Excel and in the cell next to it generate a sql query that you can perform as well from VBA.
Example: Looking up Access database in Excel
Or find a commercial tool like http://thingiequery.com/
I don't know if there's any open source tools for it.
I'm thinking that you should consider:
Say there are 100 balls.
Setting up a table to have one row for each "Draw number" with 100 columns one for every possible number each column has type boolean.
When you look to see which draws had number 23 you just add a
WHERE Column23 = true.
For numbers 23 and 56
WHERE Column23 = true AND Column56 = true
This should massivel simplify and speed up your SQL.
You set up a table with every possible combination of numbers.
You run SQL to find the counts.
Harvey
I want to pivot the example below, I'm using:
SELECT Person, GROUP_CONCAT( Var ) , GROUP_CONCAT( Val )
FROM table
GROUP BY Person
This works fine, but... it takes about 20 seconds per line and my table has +/- 2.500.000 records :-P
(BTW; the table below is an example, not the actual one)
id person Var Val
-------------------------------
1 Bob Height 185
2 Bob Weight 74
3 Bob Age 40
4 Hank Height 193
5 Hank Weight 90
6 Hank Age 45
7 Bert Height 180
8 Bert Weight 85
9 Bert Age 43
PS:
Besides an answer (what would make you awesome) I also would like to know what is 'wrong' with this example (makes you even more awesomer)
There's nothing wrong with it, except that I'd write it like this
SELECT Person, GROUP_CONCAT(CONCAT(Var, ': ', Val))
FROM table
GROUP BY Person
because when you split it up in two columns, you won't know which Val belongs to which Var.
Apart from that, do you have indexes defined on those columns? If not, play around to see which index works best, separate indexes for each column or compound indexes on person, var, val.
Let say i want to store several dataset ie
78 94 33 22 14 55 18 10 11
44 59 69 79 39 49 29 19 39
And later on i would like to be able run queries that will determine the frequency of certain number. What would be the best way to this? What would be table structure to make a fast query.
Please be specific as you can be.
To get the counts, you can run a query such as:
SELECT value, COUNT(*) from table_of_values GROUP BY value
Placing an index on the single integer value column is pretty much all you can do to speed that up.
You could of course also just keep a table with every two-digit value and a count. You will have to pre-fill the table with zero counts for every value.
Then increment the count instead of inserting:
UPDATE table_of_values SET count = count + 1 WHERE value = (whatever)