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 Posted Monday, September 27, 2010 10:48 AM
 Right there with Babe Group: General Forum Members Last Login: Tuesday, March 17, 2015 12:29 PM Points: 794, Visits: 1,197
 The discussion usually answer my questions but not this time. Doesn't "isnumeric(char(32)) as n" return 0? And if so wouldn't "select sum(n) from l" also equal 0? I guess I don't see how the sum of n got to 16 if n is alway 0? Thanks, Jerry
Post #993806
 Posted Monday, September 27, 2010 11:14 AM
 SSC-Insane Group: General Forum Members Last Login: Monday, November 21, 2016 11:03 AM Points: 20,009, Visits: 18,255
 Interesting question and great feedback from the discussion!! Jason AKA CirqueDeSQLeilI have given a name to my pain...MCM SQL Server, MVPSQL RNNRPosting Performance Based Questions - Gail Shaw
Post #993821
 Posted Monday, September 27, 2010 11:24 AM
 SSCommitted Group: General Forum Members Last Login: Wednesday, November 30, 2016 6:02 AM Points: 1,858, Visits: 2,652
 jlennartz (9/27/2010)The discussion usually answer my questions but not this time. Doesn't "isnumeric(char(32)) as n" return 0? And if so wouldn't "select sum(n) from l" also equal 0? I guess I don't see how the sum of n got to 16 if n is alway 0? Thanks, JerryJerry, the recursive CTE [i.e, "with l as ( .... )" ] creates a set of rows with the value being tested ranging from 32 to 127, so the code actually tests each character from char(32) (i.e, ' ') to char(127). There are sixteen characters in that range that can be convertible to one or more data types (usually money, as that type seems to have a very broad tolerance for conversion.) See my earlier post for a reference to recursive CTEs.
Post #993835
 Posted Monday, September 27, 2010 11:24 AM
 SSCommitted Group: General Forum Members Last Login: Friday, December 19, 2014 8:20 AM Points: 1,520, Visits: 1,060
 jlennartz (9/27/2010) I guess I don't see how the sum of n got to 16 if n is alway 0? Jerry, hopefully someone will post a tidy explanation of how a recursive CTE works. In the meantime, run this SQL to see the entire contents of the 'l' table:with l as ( select 32 as i, char(32) as s, isnumeric(char(32)) as n union all select i+1, char(i+1), isnumeric(char(i+1)) from l where i < 127)select * from lThat should help you begin to understand what's going on.
Post #993836
 Posted Monday, September 27, 2010 11:29 AM
 SSCertifiable Group: General Forum Members Last Login: Yesterday @ 1:49 AM Points: 7,765, Visits: 11,372
 jlennartz (9/27/2010)The discussion usually answer my questions but not this time. Doesn't "isnumeric(char(32)) as n" return 0? And if so wouldn't "select sum(n) from l" also equal 0? I guess I don't see how the sum of n got to 16 if n is alway 0?The start of the query is a "recursive CTE". It consists of an anchor query and a recursive query. The anchor query is:`select 32 as i, char(32) as s, isnumeric(char(32)) as n`This returns a single row, with columns 1 (integer value 32), s (char(1), value ' ' (the space character)), and column n (integer value 0, the result of ISNUMERIC(char(32))).The recursive query is:`select i+1, char(i+1), isnumeric(char(i+1)) from l where i < 127`Note that the FROM clause references the CTE itself. That makes the CTE recursive. On the first iteration, the FROM denotes the reqults of the anchor query. Since i = 32 in that row, the recursive part will now produce a similar row for the value i+1 (33). But then the recursing starts. The recursive part is evaluated again, with this new row as input, so now a row is produced that starts with i = 33 and generates column values for the value 34. This continues until the WHERE clause is no longer satisfied.[The actual execution plan will probably be more efficient than this!]The result is a table with 96 rows, with i ranging from 32 to 127 and s and n representing char(i) and isnumeri(char(i)) for each row.The outer query then sums those isnumeric values. Hugo Kornelis, SQL Server MVPVisit my SQL Server blog: http://sqlblog.com/blogs/hugo_kornelis
Post #993842
 Posted Monday, September 27, 2010 11:51 AM
 Right there with Babe Group: General Forum Members Last Login: Tuesday, March 17, 2015 12:29 PM Points: 794, Visits: 1,197
 Thank You sknox, wware and especially Hugo. With Hugo's explaination it all became clear.Thanks to all,Jerry
Post #993867
 Posted Monday, September 27, 2010 11:53 AM
 SSCommitted Group: General Forum Members Last Login: Wednesday, November 30, 2016 6:02 AM Points: 1,858, Visits: 2,652
 jlennartz (9/27/2010)...With Hugo's explaination it all became clear.It generally does.
Post #993874
 Posted Monday, September 27, 2010 6:00 PM
 SSCommitted Group: General Forum Members Last Login: Wednesday, November 30, 2016 10:34 PM Points: 1,959, Visits: 2,215
 Why does `select i+1, char(i+1), isnumeric(char(i+1)) from l where i < 127` need an i+1 in each column?
Post #994132
 Posted Tuesday, September 28, 2010 12:24 AM
 SSCertifiable Group: General Forum Members Last Login: Yesterday @ 1:49 AM Points: 7,765, Visits: 11,372
 foxxo (9/27/2010)Why does `select i+1, char(i+1), isnumeric(char(i+1)) from l where i < 127` need an i+1 in each column?If you use`select i+1, char(i), isnumeric(char(i)) from l where i < 127`Then you'd probably get the same results from the summation, but if you check the actual rows produced by the CTE, you'd see weird results. For example, when i = 80, you'd get the number 81 for the row with char(80) and isnumeric(char(80)). Hugo Kornelis, SQL Server MVPVisit my SQL Server blog: http://sqlblog.com/blogs/hugo_kornelis
Post #994203
 Posted Wednesday, September 29, 2010 1:25 AM
 Old Hand Group: General Forum Members Last Login: Wednesday, July 30, 2014 11:33 PM Points: 361, Visits: 510
 78% correct answers?! Yeah, right. Great question and good points in discussion by Hugo. Pleasure to read.But, thanks to all who participated in it.Hrvoje Hrvoje Piasevoli
Post #994960

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