In SQL, I would like to query a list, in order by pageNumber
SELECT * FROM `comics`
WHERE 1
ORDER BY pageNumber ASC
Then, I would like to set their pageNumbers based on their index in the query (starting with 1 instead of 0).
Here is my pseudo code for the functionality as desired; where list is the return value of the Select Query above.
for(var n:int = 0; n<list.length; n++){
if(list[n].pageNumber != n+1){
list[n].pageNumber = n+1
}
}
For example I might have pageNumbers 5, 17, 23, 24, 18, 7
The ORDER BY pageNumber ASC will sort this to 5, 7, 17, 18, 23, 24
I would then like to alter the pageNumbers in order to be 1, 2, 3, 4, 5, 6
edit:
#fortheworld MySQL
#cyberkiwi UPDATE
sorry for being unclear. guess i need to learn more for my questions to be clear :)
thanks for all your help
SET #I := 0;
SELECT *,
#I := #I + 1 AS newPageNumber
FROM comics
ORDER BY pageNumber ASC
I don't understand why peops insist on writing an SQL batch when a single statement will do.
SELECT comics.*, #n := #n + 1 AS PageNumber2
FROM (SELECT #n := 0) X CROSS JOIN comics
ORDER BY pageNumber ASC
Related
I have a column which I am trying to convert in MySQL into another column with a pattern where ever there are consecutive 1s in the data. Please see the example dataset below
Dataset Sample: https://1drv.ms/x/s!ApGNZAoiMmX3gi9OR7SUxt3ou84v?e=tuSV7f
Following is the code I have written but not able to make it work and any suggestions would be helpful.
select rownum,result,movingsum,new_result
(select rownum,result,movingsum,
if(result_norm_max=0,0,if(movingsum=1,1,0)) as new_result
from
(select rownum,result,
sum(result) over (order by rownum rows between 2 preceding and current row) as movingsum
from mytable) a;
The issue is, the above code doesn't return the output needed for all required logic of:
when result column is 0 new_result should be 0
when result is 1, new_result = 1 but only when previous 2 new_results are 0
Any suggestion on how I should approach this will be useful.
Thanks!
With some tries I was able to find the solution which is close to what I need as mentioned below. I used 2 variables to carry out the trick,
select rownum,result,
if (result= 0, 0, if(#n = 1, if(#m >= 7, 1 , 0), 1)) as new_max,
if (result= 0, 0, if(#n = 1,
case when #m >= 7 then #m:=0 else 0 end
, 1)) as new_max1,
if (result= 0, if(#m>0,#m:=#m-1,#m:=0), if(#n = 1, #m:=#m+1,#m:=#m-1)) as new_m,
#n := result
from mytable a, (select #n:= 0, #m:= 0) b
I have strings that are 6 characters in length and I need to test if the first character and third are the same, or the 1st and 5th or 3rd and 5th. The strings contain letters and numbers
So
aabbcc --> false
abbcad --> true
aaabcd --> true
bacada --> false
1a1b33 --> true
I need this to be part of a mysql query. Help is greatly appreciated!
The simplest (and probably fastest) way is to compare the individual substrings:
SELECT str,
SUBSTR(str, 1, 1) = SUBSTR(str, 3, 1) OR
SUBSTR(str, 1, 1) = SUBSTR(str, 5, 1) OR
SUBSTR(str, 3, 1) = SUBSTR(str, 5, 1) AS matching
FROM data
Output
str matching
aabbcc 0
abbcad 1
aaabcd 1
bacada 0
1a1b33 1
If you are running MySQL 8+ you can take advantage of the enhanced regex capability to use back-references in the pattern:
SELECT str,
REGEXP_LIKE(str, '^(.).\\1') OR
REGEXP_LIKE(str, '^(.)...\\1') OR
REGEXP_LIKE(str, '^..(.).\\1') AS matching
FROM data
Output is the same as the previous query:
str matching
aabbcc 0
abbcad 1
aaabcd 1
bacada 0
1a1b33 1
Demo on dbfiddle
You can use substring().
...
WHERE substring(nmuloc, 1, 1) = substring(nmuloc, 3, 1)
OR substring(nmuloc, 1, 1) = substring(nmuloc, 5, 1)
OR substring(nmuloc, 3, 1) = substring(nmuloc, 5, 1)
...
I am stuck at a point where i have to increment a string, and my strings are of type C001,SC001,B001
in my data base they are defined like
what i am trying to do do is write a query which check the previous highest code present into my db and the incriment it to +1
for example C001 -> C002,C009->C010,C099`->C100 and so on
Similarly for SC001->SC002,SC009->SC010,SC099->SC100 and so on
Similarly fro B001 -> B002,B009->B010,B099`->B100 and so on
I have a query which my friend has suggested me to use but that query only incriminating AAAA->AAAA01 , AAAA09->AAAA10
query is
SELECT id AS PrevID, CONCAT(
SUBSTRING(id, 1, 4),
IF(CAST(SUBSTRING(id, 5) AS UNSIGNED) <= 9, '0', ''),
CAST(SUBSTRING(id, 5) AS UNSIGNED) + 1
) AS NextID
FROM (
-- since you allow strings such as AAAA20 and AAAA100 you can no longer use MAX
SELECT id
FROM t
ORDER BY SUBSTRING(id, 1, 4) DESC, CAST(SUBSTRING(id, 5) AS UNSIGNED) DESC
LIMIT 1
) x
when i am replacing ID with CategoryCode it is giving me PrevID-C004 NextID-C00401 which is not my requirement i want PrevID-C004 and NextID->C005
NOTE i am using my sqlServer 5.1
Just try this one ,
SELECT
CategoryCode,CAST(CONCAT(LPAD(CategoryCode,1,0),LPAD(MAX(RIGHT(CategoryCode,
3)) + 1, 3, 0) ) AS CHAR),
FROM test
SELECT
SubCategoryCode,CAST(CONCAT(LPAD(SubCategoryCode,2,0),
LPAD(MAX(RIGHT(CategoryCode, 3)) + 1, 3, 0) ) AS CHAR),
FROM test
SELECT
BrandCode,CAST(CONCAT(LPAD(BrandCode,1,0), LPAD(MAX(RIGHT(BrandCode, 3)) +
1, 3, 0)) AS CHAR) FROM test
I have a mysql query:
SELECT my_table.* WHERE SOUNDEX(my_col)='whatever' OR SUBSTR(SOUNDEX(my_col),4)='whatever' ORDER BY SUBSTR(SOUNDEX(my_col),4)='whatever',SOUNDEX(my_col)='whatever'
How many times will the substring function and soundex functions will actually be called? I mean for exactly same inputs will mysql cache the results over the span of one query?
If not, how can I make the change in the query so that each function is called minimum times possible.
MySQL would call this function four times for every returned row, to avoid this you can use a subquery, so instead of
SELECT *
FROM song
ORDER BY Substr(pre_calculated_soundex, 1, 1) =
Substr(Soundex("aaaa"), 1, 1)
+ Substr(pre_calculated_soundex
, 2, 1) =
Substr
(Soundex("aaaa"), 2, 1)
+ Substr(pre_calculated_soundex, 3, 1)
= Substr(Soundex("aaaa"), 3, 1)
+ Substr(pre_calculated_soundex, 4, 1
)
= Substr(Soundex("aaaa"), 4, 1)
You can do
SELECT * from (select *, Soundex("aaaa") as current_soundex from song)
ORDER BY
Substr(pre_calculated_soundex, 1, 1) = Substr(current_soundex , 1, 1)
+ Substr(pre_calculated_soundex, 2, 1) = Substr(current_soundex , 2, 1)
+ Substr(pre_calculated_soundex, 3, 1) = Substr(current_soundex , 3, 1)
+ Substr(pre_calculated_soundex, 4, 1) = Substr(current_soundex , 4, 1)
Well, I have a table data of millions of rows. I want to carry out correlation study for every row (from the 1st to the current row minus 1). For e.g. the 1st rows is omitted. The 2nd row's result column is to be supplied with the correlation using the 1st row. The 3rd row's result column is to be supplied with the correlation using the 1st and 2nd row. And so on.
Correlation for the entire table can be calculated using:
SELECT (Count(*)*Sum(x*y)-Sum(x)*Sum(y))/
(sqrt(Count(*)*Sum(x*x)-Sum(x)*Sum(x))*
sqrt(Count(*)*Sum(y*y)-Sum(y)*Sum(y))) AS TotalCorelation FROM Data;
I want to avoid using Joins as much as possible as it takes lots of time, sometimes even timeout error, above 300 seconds). What's the other alternative?
Example table Data Structure:
id, x, y, result
1 , 4, 2, null
2 , 6, 3, -0.2312
3 , 5, 5, 0.42312
4 , 6, 2, -0.5231
5 , 5, 5, 0.22312
6 , 3, 7, -0.2312
7 , 2, 9, 0.42231
8 , 7, 2, 0.32253
9 , 9, 5, 0.32431
id : primary key
x and y : The data
result: correlation
I think this is it:
SELECT d2.ID, d2.x, d2.y, d2.result,
(Count(*)*Sum(d1.x*d1.y)-Sum(d1.x)*Sum(d1.y))/
(sqrt(Count(*)*Sum(d1.x*d1.x)-Sum(d1.x)*Sum(d1.x))*
sqrt(Count(*)*Sum(d1.y*d1.y)-Sum(d1.y)*Sum(d1.y))) AS TotalCorelation
FROM Data d1
RIGHT JOIN Data d2 ON d1.id < d2.id
GROUP BY d2.ID
ORDER BY d2.ID
Without a closed form for calculating correlation of N+1 from N rows, you have to use a quadratic join like this.
I'm assuming that your basic formula is correct. But I'm not sure it is -- when I just run it on the total dataset, I don't get the result 0.32431, I get -0.552773693079.
Here's a linear implementation:
SET #SumX = 0;
SET #SumY = 0;
SET #Count = 0;
SET #SumX2 = 0;
SET #SumY2 = 0;
SET #SumXY = 0;
SELECT id, x, y,
#SumX := #SumX + x AS SumX,
#SumY := #SumY + y AS SumY,
#Count := #Count + 1 AS ct,
#SumX2 := #SumX2 + x*x AS SumX2,
#SumY2 := #SumY2 + y*y AS SumY2,
#SumXY := #SumXY + x*y AS SumXY,
IF(#Count > 1,
(#Count*#SumXY-#SumX*#SumY)/
(sqrt(#Count*#SumX2-#SumX*#SumX)*
sqrt(#Count*#SumY2-#SumY*#SumY)), NULL) AS TotalCorelation
FROM DATA
ORDER BY id
SQLFIDDLE