Parse a String Expression into Columns - mysql

Question

I have a string for example 32,21C2L5N8C stored in one field. Now I want to expand this string into as follows:
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,CCCCCCCCCCCCCCCCCCCCCLLNNNNNCCCCCCCC
After getting the above string, I want to count number of commas,C's,L's and N's.
Can some one help me with this please?

Answer 1

you can extract the numbers and none numeric characters then then replicate each character, in SQL Server you can use patindex and replicate functions (explanations are in code):
--table variable for holding extracted numbers and none number characters
declare #t table(id int identity(1,1), num int, nonnum char(1))
declare #str1 varchar(50)='32,21C2L5N8C' -- your current given string
declare #int1 varchar(50)='' --for number
declare #str2 varchar(50)='' --for none numeric characters
declare #result varchar(max)=''
while len(#str1)>1 --for parsing the given string
begin
while (Select PatIndex('%[0-9]%', #str1))=1 --extract number
begin
set #int1=#int1+substring(#str1,1,1)
set #str1=substring(#str1,2,len(#str1)-1)
end
set #str2=substring(#str1,1,1) --extract none numeric character
set #str1=substring(#str1,2,len(#str1)-1)
insert into #t(num,nonnum)values (#int1,#str2)
set #int1=''
set #str2=''
end
select #result=#result+replicate(nonnum,num) from #t
select #result
Output:
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,CCCCCCCCCCCCCCCCCCCCCLLNNNNNCCCCCCCC
Edit 1: if you have characters with no number in front of it inside the given string and you want to print it once you can add an extra while loop in above code:
--table variable for holding extracted numbers and none number characters
declare #t table(id int identity(1,1), num int, nonnum char(1))
declare #str1 varchar(50)='32,21C2L5NC' -- your current given string
declare #int1 varchar(50)='' --for number
declare #str2 varchar(50)='' --for none numeric characters
declare #result varchar(max)=''
while len(#str1)>1 --for parsing the given string
begin
while (Select PatIndex('%[0-9]%', #str1))=1 --extract number
begin
set #int1=#int1+substring(#str1,1,1)
set #str1=substring(#str1,2,len(#str1)-1)
end
set #str2=substring(#str1,1,1) --extract none numeric character
set #str1=substring(#str1,2,len(#str1)-1)
insert into #t(num,nonnum)values (#int1,#str2)
set #int1=''
set #str2=''
while (isnumeric(substring(#str1,1,1))=0 and len(#str1)>=1)
begin
set #str2=substring(#str1,1,1) --extract none numeric character
set #str1=substring(#str1,2,len(#str1)-1)
insert into #t(num,nonnum)values (1,#str2)
set #int1=''
set #str2=''
end
end
select #result=#result+replicate(nonnum,num) from #t
select #result
Output:
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,CCCCCCCCCCCCCCCCCCCCCLLNNNNNC
Edit 2: if you want the number of repeats of each character, just query the #t table variable in above code, I mean at the end of above query say:
select nonnum [char],num [repeat] from #t
Output:
char repeat
, 32
C 21
L 2
N 5
C 1

Answer 2

You could do this by using a Pattern Splitter. Here is one taken from Dwain Camp's article. The function used, PatternSplitCM, is created by Chris Morris.
CREATE FUNCTION [dbo].[PatternSplitCM]
(
#List VARCHAR(8000) = NULL
,#Pattern VARCHAR(50)
) RETURNS TABLE WITH SCHEMABINDING
AS
RETURN
WITH numbers AS (
SELECT TOP(ISNULL(DATALENGTH(#List), 0))
n = ROW_NUMBER() OVER(ORDER BY (SELECT NULL))
FROM
(VALUES (0),(0),(0),(0),(0),(0),(0),(0),(0),(0)) d (n),
(VALUES (0),(0),(0),(0),(0),(0),(0),(0),(0),(0)) e (n),
(VALUES (0),(0),(0),(0),(0),(0),(0),(0),(0),(0)) f (n),
(VALUES (0),(0),(0),(0),(0),(0),(0),(0),(0),(0)) g (n))
SELECT
ItemNumber = ROW_NUMBER() OVER(ORDER BY MIN(n)),
Item = SUBSTRING(#List,MIN(n),1+MAX(n)-MIN(n)),
[Matched]
FROM (
SELECT n, y.[Matched], Grouper = n - ROW_NUMBER() OVER(ORDER BY y.[Matched],n)
FROM numbers
CROSS APPLY (
SELECT [Matched] = CASE WHEN SUBSTRING(#List,n,1) LIKE #Pattern THEN 1 ELSE 0 END
) y
) d
GROUP BY [Matched], Grouper
Using the function above, you would want to split your string using the pattern '[^0-9]', which means not numeric. You would then pivot the result so that the corresponding number and character will be on the same row. After that, you use REPLICATE to generate the strings and concatenate them at then end.
Your final query is:
DECLARE
#String VARCHAR(8000),
#Pattern VARCHAR(50),
#Result VARCHAR(MAX)
SELECT
#String = '32,21C2L5N8C',
#Pattern = '[^0-9]',
#Result = ''
;WITH Cte AS(
SELECT
ID = (s.ItemNumber + 1)/ 2,
Number = MAX(CASE WHEN s.ItemNumber % 2 = 1 THEN s.Item END),
Character = MAX(CASE WHEN s.ItemNumber % 2 = 0 THEN s.Item END)
FROM dbo.[PatternSplitCM](#String, #Pattern) s
GROUP BY (s.ItemNumber + 1)/ 2
)
SELECT #Result = #Result + REPLICATE(Character, Number) FROM Cte ORDER BY ID
SELECT #Result
SQL Fiddle
Here is the step by step explanation:
First, split the given string using the pattern '[^0-9]'.
SELECT * FROM dbo.[PatternSplitCM](#String, #Pattern) s
The result is:
ItemNumber Item Matched
-------------------- ---------- -----------
1 32 0
2 , 1
3 21 0
4 C 1
5 2 0
6 L 1
7 5 0
8 N 1
9 8 0
10 C 1
Second, pivot the result so that the corresponding number and character will be on the same row:
SELECT
ID = (s.ItemNumber + 1)/ 2,
Number = MAX(CASE WHEN s.ItemNumber % 2 = 1 THEN s.Item END),
Character = MAX(CASE WHEN s.ItemNumber % 2 = 0 THEN s.Item END)
FROM dbo.[PatternSplitCM](#String, #Pattern) s
GROUP BY (s.ItemNumber + 1)/ 2
The result is:
ID Number Character
------ ---------- ----------
1 32 ,
2 21 C
3 2 L
4 5 N
5 8 C
Last, use REPLICATE(Number, Character) to generate each string and concatenate them to get the final result:
SELECT #Result = #Result + REPLICATE(Character, Number) FROM Cte ORDER BY ID
SELECT #Result
The result is:
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,CCCCCCCCCCCCCCCCCCCCCLLNNNNNCCCCCCCC