Please condider the situation in which there are two tables, Body and File, in which every record of the first one has zero or more corresponding records in the second one:
BodyID | Body
-------------
1 | X
2 | Y
FileID | BodyID | File
------------------------
1 | 1 | A
2 | 1 | B
3 | 2 | C
4 | 2 | D
5 | 2 | E
Of course, it is pretty easy to join both tables and get something like
BodyID | FileID | Body | File
-----------------------------
1 | 1 | X | A
1 | 2 | X | B
2 | 3 | Y | C
2 | 4 | Y | D
2 | 5 | Y | E
However, what I would like to be able to do is to transform this same table into an horizontal one, like
BodyID | Body | File1 | File2 | File3 | ...
-------------------------------------------
1 | X | A | B | NULL | ...
2 | Y | C | D | E | ...
where each column is replaced by NULL (or any other "meaningful" value) when there are no files. The problem is that I can neither use D-SQL nor cursors. Can anyone please help me out?
whenever you need to convert your rows into columns then use pivot.you can search msdn for pivot.
Related
This question already has an answer here:
oracle - querying NULL values in unpivot query
(1 answer)
Closed 2 years ago.
I'm currently doing an unpivot for a Oracle Data Source (v.12.2) like this:
SELECT *
FROM some_table
UNPIVOT (
(X,Y,Val)
FOR SITE
IN (
(SITE1_X, SITE1_Y, SITE1_VAL) AS '1',
(SITE2_X, SITE2_Y, SITE2_VAL) AS '2',
(SITE3_X, SITE3_Y, SITE3_VAL) AS '3'
))
This works totally fine so far. There is only one exception - I have another column, let's say extend_info, ... if this column has the value y, there will be only one row of this column and all the site columns will be null. Nevertheless I would like to keep this row and not drop it.
I'm not really sure how to do this or what would be a nice way to do this. Any recommendations?
Example:
Original Table:
ID | SITE1_X | SITE1_Y |SITE1_VAL | SITE2_X | SITE2_Y | SITE2_VAL | ... | extend_info
-------
1 | 0 | 0 | 5 | 1 | 1 | 10 | ... | n
2 | 0 | 0 | 3 | null | null | null | ... | n
3 | null | null | null | null | null | null | ... | y
current output:
ID | SITE | X | Y | VAL | extend_info
-------
1 | 1 | 0 | 0 | 5 | n
2 | 1 | 1 | 1 | 10 | n
3 | 2 | 0 | 0 | 3 | n
desired output:
ID | SITE | X | Y | VAL | extend_info
-------
1 | 1 | 0 | 0 | 5 | n
2 | 1 | 1 | 1 | 10 | n
3 | 2 | 0 | 0 | 3 | n
4 | | | | | y
I don't really care what is in SITE|X|Y|VAL in that case, can be 0 for everything or null.
Bonus question:
If extend_info is y I would like to join another table with this ID. The other table looks like this:
ID | F_ID | X | Y | VAL
-----
1 | 4 | 1 | 1 | 8
2 | 4 | 2 | 2 | 9
and in that case my final output table should look like:
ID | SITE | X | Y | VAL | X_OTHER_TABLE | Y_OTHER_TABLE
-------
1 | 1 | 0 | 0 | 5 |
2 | 1 | 1 | 1 | 10 |
3 | 2 | 0 | 0 | 3 |
4 | | | | 8 | 1 | 1
5 | | | | 9 | 2 | 2
I know... the database structure is super ugly but that is what a vendor provides us and we are trying to create a View to make it easier to perform some data analysis tasks on it.
It doesn't have to look 1:1 like my final example - but maybe my itention gets clear = I want to have one single table/view with all the information in a single format.
Thanks for any help!
I would recommend a lateral join:
SELECT s.id, u.*
FROM some_table s CROSS JOIN LATERAL
(SELECT s.SITE1_X as SITE_X, s.SITE1_Y as SITE_Y, s.SITE1_VAL as SITE_VAL FROM DUAL UNION ALL
SELECT s.SITE2_X, s.SITE2_Y, s.SITE2_VAL FROM DUAL UNION ALL
SELECT s.SITE3_X, s.SITE3_Y, s.SITE3_VAL FROM DUAL
) u;
You can just join additional tables to this as you like.
I'm trying to transform data of the following form:
| ID | X | Y |
--------------
| 1 | a | m |
| 1 | b | n |
| 1 | c | o |
| 2 | d | p |
| 2 | e | q |
| 3 | f | r |
| 3 | g | s |
| 3 | h | |
To this form:
| ID | X1 | X2 | X3 | Y1 | Y2 | Y3 |
------------------------------------
| 1 | a | b | c | m | n | o |
| 2 | d | e | | p | q | |
| 3 | f | g | h | r | s | |
What is the best way to accomplish this in SQL Server 2017? Is there a better way to do transformations like this using another tool?
I don't think you can solve this problem on the DB side. You should do some backend programming. You would be able to use Pivot function, if you wanted to reverse your row values as column but you want to group them based on duplicate ids. I would solve this problem by checking duplicates by using the query below. At the results of that query, you'll be able to get max count for duplicated id. For example 1 duplicated 3 times, so you need to create a data table with 3x2+1=7 columns in your backend code. 1 stands for id column. After that you can just fill that table by checking data for each id.
WITH Temp (id, count)
AS
(
Select id, count(*)
from MyTable
group by id
having count(*)>1
)
select max(count) from Temp
I have a table with X values and Y values, both INT. What I want to do is group on the X value with the condition that it contains a distinct combination of Y values. I also want to see the total number of each combination.
I tried using SUM ( POWER (2, Y)), but that generates numbers that are too big as Y can get up to about 300 in some cases.
+--------------+--------------+
| X | Y |
+--------------+--------------+
| 1 | 1 |
| 1 | 2 |
| 1 | 4 |
| 1 | 6 |
| 2 | 1 |
| 2 | 2 |
| 2 | 4 |
| 2 | 6 |
| 3 | 2 |
| 3 | 3 |
| 3 | 5 |
| 4 | 2 |
| 4 | 3 |
| 4 | 5 |
| 5 | 2 |
| 5 | 3 |
| 5 | 6 |
+--------------+--------------+
I want the result to look something like:
+--------------+--------------+
| X | COUNT |
+--------------+--------------+
| 1 | 2 |
| 3 | 2 |
| 5 | 1 |
+--------------+--------------+
Based on your description (but not on your sample data) next query should do:
select X, count(distinct Y)
from TBL
group by X
Thanks for trying to help. I realize that it might have been hard to understand what I was trying to do.
Anyway, I ended up solving it with the checksum_agg aggregate function.
I want to perform pagination for my web page.The method that I am using (and I found mostly on internet ) is explained below with an example.
Suppose I have the following table user
+----+------+----------+
| id | name | category |
+----+------+----------+
| 1 | a | 1 |
| 2 | b | 2 |
| 3 | c | 2 |
| 4 | d | 3 |
| 5 | e | 1 |
| 6 | f | 3 |
| 7 | g | 1 |
| 8 | h | 3 |
| 9 | i | 2 |
| 10 | j | 2 |
| 11 | k | 1 |
| 12 | l | 3 |
| 13 | m | 3 |
| 14 | n | 3 |
| 15 | o | 1 |
| 16 | p | 1 |
| 17 | q | 2 |
| 18 | r | 1 |
| 19 | s | 3 |
| 20 | t | 3 |
| 21 | u | 3 |
| 22 | v | 3 |
| 23 | w | 1 |
| 24 | x | 1 |
| 25 | y | 2 |
| 26 | z | 2 |
+----+------+----------+
And I want to show information about category 3 users with 2 users per page, I am using the following query for this
select * from user where category=3 limit 0,2;
+----+------+----------+
| id | name | category |
+----+------+----------+
| 4 | d | 3 |
| 6 | f | 3 |
+----+------+----------+
and for next two
select * from user where category=3 limit 2,2;
+----+------+----------+
| id | name | category |
+----+------+----------+
| 8 | h | 3 |
| 12 | l | 3 |
+----+------+----------+
and so on.
Now in practice I have around 7000 tuples in a single table.So is there any better way in terms of speed to achieve this or in terms of any fallback this method may have.
Thanks.
You don't want to fetch more values than your current page can handle, so yes, you will essentially be making one query per page. Some other solutions (such as Rails will_paginate) will execute essentially the same queries.
Now, you could build some logic into your client side to do the pagination there - prefetch multiple (or all) pages at once and store them on the client side. This way pagination is handled completely on the client side without need for further queries. It is a bit wasteful if a user is likely to only look at a small percentage of pages overall though.
If your actual production table has more columns in it, you could select only the relevant columns instead of *, or potentially add some sort of order by (for sorting).
I hope this will help, you gotta put your page number in place of your_page_number, and records per page in place of records_per_page which in your sample is 2:
select A.* from
(select #row := #row + 1 as Row_Number, User.* from User
join (select #row := 0) Row_Temp_View
where category = 3
) A
where row_number
between (your_page_number * records_per_page)-records_per_page+1
and your_page_number * records_per_page;
notice that this will fetch you the right records, where your sample will not, and this is because your sample will fetch you always two records, which is not always true, lets say that you have 3 users you wonna show in two pages so your sample will show the first and the second in the first page and it will show the second and the third in the second page which is not right, my code will show you the first and the second in the first page and in the second page it will show you only the third one....
You can use Datatables. It's meant for exact same thing that you are looking for. I successfully use it for paginating more than a million rows, it's very fast & easy to implement.
I have a sheet like this:
| A | B | C | D | E | F | G | H | ...
---------------------------------
| a | 1 | | b | 2 | | c | 7 |
---------------------------------
| b | 2 | | c | 8 | | b | 4 |
---------------------------------
| c |289| | a | 3 | | a |118|
---------------------------------
| d | 6 | | e | 3 | | e |888|
---------------------------------
| e | 8 | | d |111| | d |553|
---------------------------------
I want the sheet to become like this:
| A | B | C | D | E | F | G | H | ...
---------------------------------
| a | 1 | 3 |118| | | | |
---------------------------------
| b | 2 | 2 | 4 | | | | |
---------------------------------
| c |289| 8 | 7 | | | | |
---------------------------------
| d | 6 |111|553| | | | |
---------------------------------
| e | 8 | 3 |888| | | | |
---------------------------------
Col A, Col B and Col G have letters which are unique, and in the col next to it it has weights.
To make it even more clear,
| A | B |
---------
| a | 1 |
---------
| b | 2 |
---------
| c |289|
...
are the weights of a,b,c... in January
Similarly | D | E | are weights of a,b,c... in July and | G | H | are weights of a,b,c... in December
I need to put them side-by-side for comparison, the thing is they are NOT in order.
How do I approach this?
UPDATE
There are thousands of a,b,c, aa, bb, cc, aaa, avb, as, saf, sfa etc.. and some of them MAY be present in January (Col A) and not in July (Col D)
Something like this
code
Sub Squeeze()
[c1:c5] = Application.Index([E1:E5], Evaluate("IF(A1:A5<>"""",MATCH(A1:A5,D1:D5,0),A1:A5)"), 1)
[d1:d5] = Application.Index([H1:h5], Evaluate("IF(A1:A5<>"""",MATCH(A1:A5,G1:G5,0),A1:A5)"), 1)
[e1:h5].ClearContents
End Sub
Explanation of first line
Application.Index([E1:E5], Evaluate("IF(A1:A5<>"""",MATCH(A1:A5,D1:D5,0),A1:A5)"), 1)
The MATCH returns a VBA array matching the positions (5) of A1:A5 against D1:D5
INDEX then returns the corresponding values from E1:E5
So to use the key column of A1:A100 against M1:100 with values in N1:100
Application.Index([N1:N100], Evaluate("IF(A1:A100<>"""",MATCH(A1:A100,M1:M100,0),A1:A100)"), 1)
Extend as necessary: Sort D:E by D ascending, sort G:H by G ascending, delete G,F,D,C. If you want VBA, do this with Record Macro selected.