SQL, finding discrete overlapping time intervals o

Question

I'm working in SQL Server Management Studio so I suppose this is a Microsoft SQL Server T-SQL question.

The real world scenario is this: I have multiple employees working across multiple locations and the "time in" and "time out" records for each. I have already created a unique "Shift ID" for each set of time intervals and joined, based on employee, date, and location the shifts of other employees that match my keystone employee, or the one against which I am comparing everyone else.

Furthermore, I have written a query that pulled each "other employee's" specific overlapping time interval with the keystone. For one shift the timeline looks like this:

 Key Emp. | 9AM------------------------6PM
 Emp. A   | 9AM------------------------6PM
 Emp. B   |         12PM-------4PM        

So the discrete periods where a true "controlled" comparison can be made are among:

• Key, A, and B from 12PM - 4PM
• Key and A from 9AM - 12PM
• Key and A from 4PM - 6PM

The end goal is to pull all the activity (organized as events with datetime stamps in a separate table) for each employee that occurs within those time periods and compare totals for each relevant employee. So there would be a separate "Count(events)" total for each time frame only affected by the employees that share the time interval as described above.

Currently, my data is organized like this:

the "In" and "Out" columns for key and other employees are stored as TIMESTAMPs; the "1/1,6PM" is just my crappy way of saving space in my example. Please see my consumable data at the end of this post. SSMS doesn't seem to care that I have more than TIMESTAMP column and treats them all like DATETIME:

Key_ShiftID| Key In | Key Out | Oth_Emp_ShiftID | Oth_Emp_In | Oth_Emp_Out
  K          1/1,9AM   1/1,6PM     A                1/1,9AM     1/1,6PM 
  K          1/1,9AM   1/1,6PM     B                1/1,12PM    1/1,4PM 

Where the Shift IDs (Key_ShiftID and Oth_Emp_ShiftID) are unique strings and the time intervals are defined by two columns a piece (Key_In & Key_Out + Oth_Emp_In & Oth_Emp_Out) are stored as datetime/timestamps. I'm looking for discrete periods where I can compare the activity of the employees, which is in a separate table with each event having a unique datetime as was mentioned earlier. Thus, I think the ending data would look something like this:

Key_ShiftID| Key_In | Key_Out | Oth_Emp_ShiftID | Oth_Emp_In  | Oth_Emp_Out
  K          1/1,9AM   1/1,6PM     A                1/1,12PM    1/1,4PM 
  K          1/1,9AM   1/1,6PM     B                1/1,12PM    1/1,4PM 
  K          1/1,9AM   1/1,6PM     A                1/1,9AM     1/1,12PM
  K          1/1,9AM   1/1,6PM     A                1/1,4PM     1/1,6PM

So I would be able to join the table above to my activity table by ShiftID and bring in the Count(events) per relevant employee

where event_datetime >= Oth_Emp_In and event_datetime <= Oth_Emp_Out

Additionally, as I noted before, I already wrote a query to cut down the non-key employees' shifts to reflect only the time intervals where they overlap with the key employee, so the Other_Emp_In will always be greater than or equal to the Key In time and Other_Emp_Out will always be less than or equal to the Key Out time.

Thanks in advance. I've been researching and struggling with this for around 2 days.

Here's sample data of one key shift (not the exact example above):

Also, SQL Server doesn't seem to care that I have more than TIMESTAMP column and treats them all like DATETIME.

CREATE TABLE "sample_data" 
(
    "Employee" INT,
    "Key_ShiftID" TEXT,
    "Key_In" TIMESTAMP,
    "Key_Out" TIMESTAMP,
    "Other_Emp_ShiftID" TEXT,
    "Other_Emp_In" TIMESTAMP,
    "Other_Emp_Out" TIMESTAMP,
    "overlap_min" TIMESTAMP,
    "overlap_max" TIMESTAMP
);

INSERT INTO "sample_data" 
VALUES (900, '545BD826-0C9A-408B-BE9F-4C3D7D307948', '2016-09-27 14:15:00', '2016-09-27 21:45:00', '035FA1C1-B469-44EB-B5B4-5B6948574464', '2016-09-27 08:45:00', '2016-09-27 16:15:00', '2016-09-27 14:15:00', '2016-09-27 16:15:00'),
       (78, '545BD826-0C9A-408B-BE9F-4C3D7D307948', '2016-09-27 14:15:00', '2016-09-27 21:45:00', '74035838-FD07-4F8D-8AC4-F6407AC786D9', '2016-09-27 18:00:00', '2016-09-27 21:15:00', '2016-09-27 18:00:00', '2016-09-27 21:15:00'),
       (900, '545BD826-0C9A-408B-BE9F-4C3D7D307948', '2016-09-27 14:15:00', '2016-09-27 21:45:00', 'D7E9ADCD-8631-476D-B69F-00626F0E4B06', '2016-09-27 16:45:00', '2016-09-27 21:45:00', '2016-09-27 16:45:00', '2016-09-27 21:45:00');

Answer 1

Welcome to StackOverflow. In the future, try to include some easily consumable sample data like what I am including in my solution below.

This is a fun little problem. For this kind of thing I leverage my patExtract8K function which leverages ngrams8K. Here's an example of how to use PatExtract; here I'm extracting money from a string:

SELECT p.* 
FROM   dbo.patextract8K('Pay me $50.17 now or $1000 later!','[^$0-9.]') AS p;

Results:

itemNumber  itemIndex  itemLength  item
----------- ---------- ----------- --------
1           8          6           $50.17
2           22         5           $1000

Now to tackle your problem:

-- Easily consumable sample data
DECLARE @table TABLE (shiftId VARCHAR(2), empKey VARCHAR(5), workDuration VARCHAR(100));
INSERT @table(shiftId,empKey,workDuration)
VALUES
('K','A','12PM - 4PM'),
('K','B','12PM - 4PM'),
('K','A','9AM - 12PM'),
('K','A','4PM - 6PM');

-- Solution
SELECT 
  shiftId   = f.shiftId, 
  KeyIn     = '1/1,'+REPLACE(CONVERT(VARCHAR(10),
               MIN(CAST(f.c1 AS TIME)) OVER (),100),':00',''),
  KeyOut    = '1/1,'+REPLACE(CONVERT(VARCHAR(10),
               MAX(CAST(f.c2 AS TIME)) OVER (),100),':00',''),
  empShift  = f.empKey,
    othEmpIn  = '1/1,'+f.c1, 
  othEmpOut = '1/1,'+f.c2
FROM
(
  SELECT      t.shiftId, t.empKey, t.workDuration, 
              c1 = MAX(CASE p.itemNumber WHEN 1 THEN p.item END), 
              c2 = MAX(CASE p.itemNumber WHEN 2 THEN p.item END)
  FROM        @table AS t
  CROSS APPLY dbo.patExtract8k(t.workDuration, '[^0-9APM]') AS p
  CROSS APPLY (VALUES(CAST(p.item AS TIME))) AS tm(N)
  GROUP BY    t.shiftId, t.empKey, t.workDuration
) AS f;

Results:

shiftId KeyIn      KeyOut       empShift othEmpIn     othEmpOut
------- ---------- ------------ -------- ------------ ------------
K       1/1,9AM    1/1,6PM      A        1/1,12PM     1/1,4PM
K       1/1,9AM    1/1,6PM      A        1/1,4PM      1/1,6PM
K       1/1,9AM    1/1,6PM      A        1/1,9AM      1/1,12PM
K       1/1,9AM    1/1,6PM      B        1/1,12PM     1/1,4PM

Note that I have no idea where the "1/1" is coming from so I just hard-coded that in.

Here's my underlying functions. All are very helpful for solving a wide array of SQL issues efficiently and with little code.

CREATE FUNCTION dbo.rangeAB
(
  @low  bigint, 
  @high bigint, 
  @gap  bigint,
  @row1 bit
)
/****************************************************************************************
[Purpose]:
 Creates up to 531,441,000,000 sequentia1 integers numbers beginning with @low and ending 
 with @high. Used to replace iterative methods such as loops, cursors and recursive CTEs 
 to solve SQL problems. Based on Itzik Ben-Gan's getnums function with some tweeks and 
 enhancements and added functionality. The logic for getting rn to begin at 0 or 1 is 
 based comes from Jeff Moden's fnTally function. 

 The name range because it's similar to clojure's range function. The name "rangeAB" as 
 used because "range" is a reserved SQL keyword.

[Author]: Alan Burstein

[Compatibility]: 
 SQL Server 2008+ and Azure SQL Database

[Syntax]:
 SELECT r.RN, r.OP, r.N1, r.N2
 FROM dbo.rangeAB(@low,@high,@gap,@row1) AS r;

[Parameters]:
 @low  = a bigint that represents the lowest value for n1.
 @high = a bigint that represents the highest value for n1.
 @gap  = a bigint that represents how much n1 and n2 will increase each row; @gap also
         represents the difference between n1 and n2.
 @row1 = a bit that represents the first value of rn. When @row = 0 then rn begins
         at 0, when @row = 1 then rn will begin at 1.

[Returns]:
 Inline Table Valued Function returns:
 rn = bigint; a row number that works just like T-SQL ROW_NUMBER() except that it can 
      start at 0 or 1 which is dictated by @row1.
 op = bigint; returns the "opposite number that relates to rn. When rn begins with 0 and
      ends with 10 then 10 is the opposite of 0, 9 the opposite of 1, etc. When rn begins
      with 1 and ends with 5 then 1 is the opposite of 5, 2 the opposite of 4, etc...
 n1 = bigint; a sequential number starting at the value of @low and incrimentingby the
      value of @gap until it is less than or equal to the value of @high.
 n2 = bigint; a sequential number starting at the value of @low+@gap and  incrimenting 
      by the value of @gap.

[Dependencies]:
N/A

[Developer Notes]:

 1. The lowest and highest possible numbers returned are whatever is allowable by a 
    bigint. The function, however, returns no more than 531,441,000,000 rows (8100^3). 
 2. @gap does not affect rn, rn will begin at @row1 and increase by 1 until the last row
    unless its used in a query where a filter is applied to rn.
 3. @gap must be greater than 0 or the function will not return any rows.
 4. Keep in mind that when @row1 is 0 then the highest row-number will be the number of
    rows returned minus 1
 5. If you only need is a sequential set beginning at 0 or 1 then, for best performance
    use the RN column. Use N1 and/or N2 when you need to begin your sequence at any 
    number other than 0 or 1 or if you need a gap between your sequence of numbers. 
 6. Although @gap is a bigint it must be a positive integer or the function will
    not return any rows.
 7. The function will not return any rows when one of the following conditions are true:
      * any of the input parameters are NULL
      * @high is less than @low 
      * @gap is not greater than 0
    To force the function to return all NULLs instead of not returning anything you can
    add the following code to the end of the query:

      UNION ALL 
      SELECT NULL, NULL, NULL, NULL
      WHERE NOT (@high&@low&@gap&@row1 IS NOT NULL AND @high >= @low AND @gap > 0)

    This code was excluded as it adds a ~5% performance penalty.
 8. There is no performance penalty for sorting by rn ASC; there is a large performance 
    penalty for sorting in descending order WHEN @row1 = 1; WHEN @row1 = 0
    If you need a descending sort the use op in place of rn then sort by rn ASC. 

Best Practices:
--===== 1. Using RN (rownumber)
 -- (1.1) The best way to get the numbers 1,2,3...@high (e.g. 1 to 5):
 SELECT RN FROM dbo.rangeAB(1,5,1,1);
 -- (1.2) The best way to get the numbers 0,1,2...@high-1 (e.g. 0 to 5):
 SELECT RN FROM dbo.rangeAB(0,5,1,0);

--===== 2. Using OP for descending sorts without a performance penalty
 -- (2.1) The best way to get the numbers 5,4,3...@high (e.g. 5 to 1):
 SELECT op FROM dbo.rangeAB(1,5,1,1) ORDER BY rn ASC;
 -- (2.2) The best way to get the numbers 0,1,2...@high-1 (e.g. 5 to 0):
 SELECT op FROM dbo.rangeAB(1,6,1,0) ORDER BY rn ASC;

--===== 3. Using N1
 -- (3.1) To begin with numbers other than 0 or 1 use N1 (e.g. -3 to 3):
 SELECT N1 FROM dbo.rangeAB(-3,3,1,1);
 -- (3.2) ROW_NUMBER() is built in. If you want a ROW_NUMBER() include RN:
 SELECT RN, N1 FROM dbo.rangeAB(-3,3,1,1);
 -- (3.3) If you wanted a ROW_NUMBER() that started at 0 you would do this:
 SELECT RN, N1 FROM dbo.rangeAB(-3,3,1,0);

--===== 4. Using N2 and @gap
 -- (4.1) To get 0,10,20,30...100, set @low to 0, @high to 100 and @gap to 10:
 SELECT N1 FROM dbo.rangeAB(0,100,10,1);
 -- (4.2) Note that N2=N1+@gap; this allows you to create a sequence of ranges.
 --       For example, to get (0,10),(10,20),(20,30).... (90,100):
 SELECT N1, N2 FROM dbo.rangeAB(0,90,10,1);
 -- (4.3) Remember that a rownumber is included and it can begin at 0 or 1:
 SELECT RN, N1, N2 FROM dbo.rangeAB(0,90,10,1);

[Examples]:
--===== 1. Generating Sample data (using rangeAB to create "dummy rows")
 -- The query below will generate 10,000 ids and random numbers between 50,000 and 500,000
 SELECT
   someId    = r.rn,
   someNumer = ABS(CHECKSUM(NEWID())%450000)+50001 
 FROM rangeAB(1,10000,1,1) r;

--===== 2. Create a series of dates; rn is 0 to include the first date in the series
 DECLARE @startdate DATE = '20180101', @enddate DATE = '20180131';

 SELECT r.rn, calDate = DATEADD(dd, r.rn, @startdate)
 FROM dbo.rangeAB(1, DATEDIFF(dd,@startdate,@enddate),1,0) r;
 GO

--===== 3. Splitting (tokenizing) a string with fixed sized items
 -- given a delimited string of identifiers that are always 7 characters long
 DECLARE @string VARCHAR(1000) = 'A601225,B435223,G008081,R678567';

 SELECT
   itemNumber = r.rn, -- item's ordinal position 
   itemIndex  = r.n1, -- item's position in the string (it's CHARINDEX value)
   item       = SUBSTRING(@string, r.n1, 7) -- item (token)
 FROM dbo.rangeAB(1, LEN(@string), 8,1)  r;
 GO

--===== 4. Splitting (tokenizing) a string with random delimiters
 DECLARE @string VARCHAR(1000) = 'ABC123,999F,XX,9994443335';

 SELECT
   itemNumber = ROW_NUMBER() OVER (ORDER BY r.rn), -- item's ordinal position 
   itemIndex  = r.n1+1, -- item's position in the string (it's CHARINDEX value)
   item       = SUBSTRING
               (
                 @string,
                 r.n1+1,
                 ISNULL(NULLIF(CHARINDEX(',',@string,r.n1+1),0)-r.n1-1, 8000)
               ) -- item (token)
 FROM dbo.rangeAB(0,DATALENGTH(@string),1,1) r
 WHERE SUBSTRING(@string,r.n1,1) = ',' OR r.n1 = 0;
 -- logic borrowed from: http://www.sqlservercentral.com/articles/Tally+Table/72993/

--===== 5. Grouping by a weekly intervals
 -- 5.1. how to create a series of start/end dates between @startDate & @endDate
 DECLARE @startDate DATE = '1/1/2015', @endDate DATE = '2/1/2015';
 SELECT 
   WeekNbr   = r.RN,
   WeekStart = DATEADD(DAY,r.N1,@StartDate), 
   WeekEnd   = DATEADD(DAY,r.N2-1,@StartDate)
 FROM dbo.rangeAB(0,datediff(DAY,@StartDate,@EndDate),7,1) r;
 GO

 -- 5.2. LEFT JOIN to the weekly interval table
 BEGIN
  DECLARE @startDate datetime = '1/1/2015', @endDate datetime = '2/1/2015';
  -- sample data 
  DECLARE @loans TABLE (loID INT, lockDate DATE);
  INSERT @loans SELECT r.rn, DATEADD(dd, ABS(CHECKSUM(NEWID())%32), @startDate)
  FROM dbo.rangeAB(1,50,1,1) r;

  -- solution 
  SELECT 
    WeekNbr   = r.RN,
    WeekStart = dt.WeekStart, 
    WeekEnd   = dt.WeekEnd,
    total     = COUNT(l.lockDate)
  FROM dbo.rangeAB(0,datediff(DAY,@StartDate,@EndDate),7,1) r
  CROSS APPLY (VALUES (
    CAST(DATEADD(DAY,r.N1,@StartDate) AS DATE), 
    CAST(DATEADD(DAY,r.N2-1,@StartDate) AS DATE))) dt(WeekStart,WeekEnd)
  LEFT JOIN @loans l ON l.lockDate BETWEEN  dt.WeekStart AND dt.WeekEnd
  GROUP BY r.RN, dt.WeekStart, dt.WeekEnd ;
 END;

--===== 6. Identify the first vowel and last vowel in a along with their positions
 DECLARE @string VARCHAR(200) = 'This string has vowels';

 SELECT TOP(1) position = r.rn, letter = SUBSTRING(@string,r.rn,1)
 FROM dbo.rangeAB(1,LEN(@string),1,1) r
 WHERE SUBSTRING(@string,r.rn,1) LIKE '%[aeiou]%'
 ORDER BY r.rn;

 -- To avoid a sort in the execution plan we'll use op instead of rn
 SELECT TOP(1) position = r.op, letter = SUBSTRING(@string,r.op,1)
 FROM dbo.rangeAB(1,LEN(@string),1,1) r
 WHERE SUBSTRING(@string,r.rn,1) LIKE '%[aeiou]%'
 ORDER BY r.rn;

---------------------------------------------------------------------------------------
[Revision History]:
 Rev 00 - 20140518 - Initial Development - Alan Burstein
 Rev 01 - 20151029 - Added 65 rows to make L1=465; 465^3=100.5M. Updated comment section
                   - Alan Burstein
 Rev 02 - 20180613 - Complete re-design including opposite number column (op)
 Rev 03 - 20180920 - Added additional CROSS JOIN to L2 for 530B rows max - Alan Burstein
****************************************************************************************/
RETURNS TABLE WITH SCHEMABINDING AS RETURN
WITH L1(N) AS 
(
  SELECT 1
  FROM (VALUES
   (0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),
   (0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),
   (0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),
   (0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),(0),
   (0),(0)) T(N) -- 90 values 
),
L2(N)  AS (SELECT 1 FROM L1 a CROSS JOIN L1 b CROSS JOIN L1 c),
iTally AS (SELECT rn = ROW_NUMBER() OVER (ORDER BY (SELECT 1)) FROM L2 a CROSS JOIN L2 b)
SELECT  
  r.RN,
  r.OP,
  r.N1,
  r.N2
FROM
(
  SELECT
    RN = 0,
    OP = (@high-@low)/@gap,
    N1 = @low,
    N2 = @gap+@low
  WHERE @row1 = 0
  UNION ALL -- COALESCE required in the TOP statement below for error handling purposes
  SELECT TOP (ABS((COALESCE(@high,0)-COALESCE(@low,0))/COALESCE(@gap,0)+COALESCE(@row1,1)))
    RN = i.rn,
    OP = (@high-@low)/@gap+(2*@row1)-i.rn,
    N1 = (i.rn-@row1)*@gap+@low,
    N2 = (i.rn-(@row1-1))*@gap+@low
  FROM iTally AS i
  ORDER BY rn
) AS r
WHERE @high&@low&@gap&@row1 IS NOT NULL AND @high >= @low AND @gap > 0;
GO

IF OBJECT_ID('dbo.NGrams8k', 'IF') IS NOT NULL DROP FUNCTION dbo.NGrams8k;
GO
CREATE FUNCTION dbo.NGrams8k
(
  @string VARCHAR(8000), -- Input string
  @N      INT            -- requested token size
)
/*****************************************************************************************
[Purpose]:
 A character-level N-Grams function that outputs a contiguous stream of @N-sized tokens
 based on an input string (@string). Accepts strings up to 8000 varchar characters long.
 For more information about N-Grams see: http://en.wikipedia.org/wiki/N-gram.

[Author]: 
 Alan Burstein

[Compatibility]:
 SQL Server 2008+, Azure SQL Database

[Syntax]:
--===== Autonomous
 SELECT ng.position, ng.token 
 FROM   dbo.NGrams8k(@string,@N) AS ng;

--===== Against a table using APPLY
 SELECT      s.SomeID, ng.position, ng.token
 FROM        dbo.SomeTable AS s
 CROSS APPLY dbo.NGrams8K(s.SomeValue,@N) AS ng;

[Parameters]:
 @string  = The input string to split into tokens.
 @N       = The size of each token returned.

[Returns]:
 Position = BIGINT; the position of the token in the input string
 token    = VARCHAR(8000); a @N-sized character-level N-Gram token

[Dependencies]:
 1. dbo.rangeAB (iTVF)

[Developer Notes]:
 1. NGrams8k is not case sensitive;

 2. Many functions that use NGrams8k will see a huge performance gain when the optimizer
    creates a parallel execution plan. One way to get a parallel query plan (if the
    optimizer does not choose one) is to use make_parallel by Adam Machanic which can be
    found here:
 sqlblog.com/blogs/adam_machanic/archive/2013/07/11/next-level-parallel-plan-porcing.aspx

3. When @N is less than 1 or greater than the datalength of the input string then no
    tokens (rows) are returned. If either @string or @N are NULL no rows are returned.
    This is a debatable topic but the thinking behind this decision is that: because you
    can't split 'xxx' into 4-grams, you can't split a NULL value into unigrams and you
    can't turn anything into NULL-grams, no rows should be returned.

    For people who would prefer that a NULL input forces the function to return a single
    NULL output you could add this code to the end of the function:

    UNION ALL
    SELECT 1, NULL
    WHERE NOT(@N > 0 AND @N <= DATALENGTH(@string)) OR (@N IS NULL OR @string IS NULL)

 4. NGrams8k is deterministic. For more about deterministic functions see:
    https://msdn.microsoft.com/en-us/library/ms178091.aspx

[Examples]:
--===== 1. Split the string, "abcd" into unigrams, bigrams and trigrams
 SELECT ng.position, ng.token FROM dbo.NGrams8k('abcd',1) AS ng; -- unigrams (@N=1)
 SELECT ng.position, ng.token FROM dbo.NGrams8k('abcd',2) AS ng; -- bigrams  (@N=2)
 SELECT ng.position, ng.token FROM dbo.NGrams8k('abcd',3) AS ng; -- trigrams (@N=3)

--===== How many times the substring "AB" appears in each record
 DECLARE @table TABLE(stringID int identity primary key, string varchar(100));
 INSERT @table(string) VALUES ('AB123AB'),('123ABABAB'),('!AB!AB!'),('AB-AB-AB-AB-AB');

 SELECT      string, occurances = COUNT(*)
 FROM        @table t
 CROSS APPLY dbo.NGrams8k(t.string,2) AS ng
 WHERE       ng.token = 'AB'
 GROUP BY    string;

[Revision History]:
------------------------------------------------------------------------------------------
 Rev 00 - 20140310 - Initial Development - Alan Burstein
 Rev 01 - 20150522 - Removed DQS N-Grams functionality, improved iTally logic. Also Added
                     conversion to bigint in the TOP logic to remove implicit conversion
                     to bigint - Alan Burstein
 Rev 03 - 20150909 - Added logic to only return values if @N is greater than 0 and less
                     than the length of @string. Updated comment section. - Alan Burstein
 Rev 04 - 20151029 - Added ISNULL logic to the TOP clause for the @string and @N
                     parameters to prevent a NULL string or NULL @N from causing "an
                     improper value" being passed to the TOP clause. - Alan Burstein
 Rev 05 - 20171228 - Small simplification; changed: 
                (ABS(CONVERT(BIGINT,(DATALENGTH(ISNULL(@string,''))-(ISNULL(@N,1)-1)),0)))
                                           to:
                (ABS(CONVERT(BIGINT,(DATALENGTH(ISNULL(@string,''))+1-ISNULL(@N,1)),0)))
 Rev 06 - 20180612 - Using CHECKSUM(N) in the to convert N in the token output instead of
                     using (CAST N as int). CHECKSUM removes the need to convert to int.
 Rev 07 - 20180612 - re-designed to: (1) use dbo.rangeAB - Alan Burstein
****************************************************************************************/
RETURNS TABLE WITH SCHEMABINDING AS RETURN
SELECT
  position   = r.RN,
  token      = SUBSTRING(@string, CHECKSUM(r.RN), @N)
FROM  dbo.rangeAB(1, LEN(@string)+1-@N,1,1) AS r
WHERE @N > 0 AND @N <= LEN(@string);
GO

CREATE FUNCTION dbo.patExtract8K
(
  @string  VARCHAR(8000),
  @pattern VARCHAR(50)
)
/*****************************************************************************************
[Description]:
 This can be considered a T-SQL inline table valued function (iTVF) equivalent of 
 Microsoft's mdq.RegexExtract except:

 1. It includes each matching substring's position in the string

 2. It accepts varchar(8000) instead of nvarchar(4000) for the input string, varchar(50)
    instead of nvarchar(4000) for the pattern

 3. The mask parameter is not required and therefore does not exist.

 4. You have specify what text we're searching for as an exclusion; e.g. for numeric 
    characters you should search for '[^0-9]' instead of '[0-9]'. 

 5. There is is no parameter for naming a "capture group". Using the variable below, both 
    the following queries will return the same result:

     DECLARE @string nvarchar(4000) = N'123 Main Street';

   SELECT item FROM dbo.patExtract8K(@string, '[^0-9]');
   SELECT clr.RegexExtract(@string, N'(?<number>(\d+))(?<street>(.*))', N'number', 1);

 Alternatively, you can think of patExtract8K as Chris Morris' PatternSplitCM (found here:
 http://www.sqlservercentral.com/articles/String+Manipulation/94365/) but only returns the
 rows where [matched]=0. The key benefit of is that it performs substantially better 
 because you are only returning the number of rows required instead of returning twice as
 many rows then filtering out half of them.  Furthermore, because we're 

 The following two sets of queries return the same result:

 DECLARE @string varchar(100) = 'xx123xx555xx999';
 BEGIN
 -- QUERY #1
   -- patExtract8K
   SELECT ps.itemNumber, ps.item 
   FROM dbo.patExtract8K(@string, '[^0-9]') ps;

   -- patternSplitCM   
   SELECT itemNumber = row_number() over (order by ps.itemNumber), ps.item 
   FROM dbo.patternSplitCM(@string, '[^0-9]') ps
   WHERE [matched] = 0;

 -- QUERY #2
   SELECT ps.itemNumber, ps.item 
   FROM dbo.patExtract8K(@string, '[0-9]') ps;

   SELECT itemNumber = row_number() over (order by itemNumber), item 
   FROM dbo.patternSplitCM(@string, '[0-9]')
   WHERE [matched] = 0;
 END;

[Compatibility]:
 SQL Server 2008+

[Syntax]:
--===== Autonomous
 SELECT pe.ItemNumber, pe.ItemIndex, pe.ItemLength, pe.Item
 FROM dbo.patExtract8K(@string,@pattern) pe;

--===== Against a table using APPLY
 SELECT t.someString, pe.ItemIndex, pe.ItemLength, pe.Item
 FROM dbo.SomeTable t
 CROSS APPLY dbo.patExtract8K(t.someString, @pattern) pe;

[Parameters]:
 @string        = varchar(8000); the input string
 @searchString  = varchar(50); pattern to search for

[Returns]:
 itemNumber = bigint; the instance or ordinal position of the matched substring
 itemIndex  = bigint; the location of the matched substring inside the input string
 itemLength = int; the length of the matched substring
 item       = varchar(8000); the returned text

[Developer Notes]:
 1. Requires NGrams8k 

 2. patExtract8K does not return any rows on NULL or empty strings. Consider using 
    OUTER APPLY or append the function with the code below to force the function to return 
    a row on emply or NULL inputs:

    UNION ALL SELECT 1, 0, NULL, @string WHERE nullif(@string,'') IS NULL;

 3. patExtract8K is not case sensitive; use a case sensitive collation for 
    case-sensitive comparisons

 4. patExtract8K is deterministic. For more about deterministic functions see:
    https://msdn.microsoft.com/en-us/library/ms178091.aspx

 5. patExtract8K performs substantially better with a parallel execution plan, often
    2-3 times faster. For queries that leverage patextract8K that are not getting a 
    parallel exeution plan you should consider performance testing using Traceflag 8649 
    in Development environments and Adam Machanic's make_parallel in production. 

[Examples]:
--===== (1) Basic extact all groups of numbers:
  WITH temp(id, txt) as
 (
   SELECT * FROM (values
   (1, 'hello 123 fff 1234567 and today;""o999999999 tester 44444444444444 done'),
   (2, 'syat 123 ff tyui( 1234567 and today 999999999 tester 777777 done'),
   (3, '&**OOOOO=+ + + // ==?76543// and today !!222222\\\tester{}))22222444 done'))t(x,xx)
 )
 SELECT
   [temp.id] = t.id,
   pe.itemNumber,
   pe.itemIndex,
   pe.itemLength,
   pe.item
 FROM        temp AS t
 CROSS APPLY dbo.patExtract8K(t.txt, '[^0-9]') AS pe;
-----------------------------------------------------------------------------------------
Revision History:
 Rev 00 - 20170801 - Initial Development - Alan Burstein
 Rev 01 - 20180619 - Complete re-write   - Alan Burstein
*****************************************************************************************/
RETURNS TABLE WITH SCHEMABINDING AS RETURN
SELECT itemNumber = ROW_NUMBER() OVER (ORDER BY f.position),
       itemIndex  = f.position,
       itemLength = itemLen.l,
       item       = SUBSTRING(f.token, 1, itemLen.l)
FROM
(
 SELECT ng.position, SUBSTRING(@string,ng.position,DATALENGTH(@string))
 FROM   dbo.NGrams8k(@string, 1) AS ng
 WHERE  PATINDEX(@pattern, ng.token) <  --<< this token does NOT match the pattern
        ABS(SIGN(ng.position-1)-1) +    --<< are you the first row?  OR
        PATINDEX(@pattern,SUBSTRING(@string,ng.position-1,1)) --<< always 0 for 1st row
) AS f(position, token)
CROSS APPLY (VALUES(ISNULL(NULLIF(PATINDEX('%'+@pattern+'%',f.token),0),
  DATALENGTH(@string)+2-f.position)-1)) AS itemLen(l);
GO