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Re: insert label into file

by kennethk (Abbot)
on Mar 20, 2009 at 15:15 UTC ( #752079=note: print w/replies, xml ) Need Help??

in reply to insert label into file

Answering your second question, you have two syntax errors in the provided code. First, by including my in your assignment statement, you are masking the $value variable declared in your while statement (This will get caught if you use strict;use warnings). Second, you are overwriting your %copy hash on every iteration with the new key-value pair. What you mean is likely:

use strict; use warnings; my %copy = (); while ( my ($key, $value) = each(%hash) ) { $copy{$value} = $key; }

This can be done in one line as:

my %copy = reverse %hash;

Be aware that this will not behave well if you have repeat values.

Update: This is addressed in perlfaq4.

Replies are listed 'Best First'.
Re^2: insert label into file
by grashoper (Monk) on Mar 20, 2009 at 16:32 UTC
    I have repeat values, I read this but now I don't know how to proceed.. If your hash could have repeated values, the methods above will only find one of the associated keys. This may or may not worry you. If it does worry you, you can always reverse the hash into a hash of arrays instead:
    while (($key, $value) = each %by_key) { push @{$key_list_by_value{$value}}, $key; }
    I am confused enough just using hash, hash of arrays, can I put it back into a hash somehow?, reason I want the hash is to input the data into a table in sql, using sql abstract, which looks like it should work for my purpose to store this data in a db, maybe I could somehow fix my data file to be correct by changing the way information is logged so that its numbers then names by using regexes to move the labels I have around.
      The repeat values in your hash mean that you cannot use them as primary keys for identifying a data set. Clever data structures in Perl will not help you if you are trying to use them as the keys in your database. There are a couple possible solutions here, depending on your needs. The most natural solution is to use whatever you index your database with to key your hash. Can you provide your db table structure, some sample data from your original hash and explain how they are related?
        well let me clarify a bit here. My hash is backwards, data file example is below. Database has columns for Date,Login,SearchLoad,etc, Date column is a date/time login real searchload real when I read file into hash I get timevalue->columnname, I want the reverse which would be columname->timevalue. In order to fix my data file, I want to add a label Date to the first value which is a timestamp for each record throughout the file, then I want to read the file into a hash so I can input it into the database which is currently empty and only contains the columns I want to use for the table. The sql for the table creation is in the bottom of this comment.
        05/12/2006 12:21:10 AM,Login,19.748396,SearchLoad,13.459355,SearchCoun +t,64:0.660950,SearchResults,12.988677,SearchSave,6.138828,SearchDelet +e,1.682419,SearchDetails,10.114545,TaxLoad,3.995745,TaxResults,567:5. +287602,TaxDetails,3.975717,ClientAdd,2.643801,CMALoad,2.603744,CMASav +e,14.350635,CMADelete,1.021467,ClientDelete,0.731053,Logout,2.733931, +05/12/2006 12:54:07 AM,Login,18.015907,SearchLoad,13.259065,SearchCou +nt,64:0.620893,SearchResults,12.187526,SearchSave,5.327662,SearchDele +te,1.111600,SearchDetails,9.914256,TaxLoad,3.755399,TaxResults,567:5. +047257,TaxDetails,4.055832,ClientAdd,2.583715,CMALoad,2.834077,CMASav +e,14.350636,CMADelete,0.690993,ClientDelete,0.610879,Logout,2.743947, +05/12/2006 01:21:15 AM,
        database stuff..
        USE [performancetesting] GO /****** Object: Table [dbo].[AllResults] Script Date: 03/20/2009 1 +3:35:27 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[AllResults]( [Date] [datetime] NOT NULL, [Login] [real] NULL, [SearchLoad] [real] NULL, [SearchCount] [real] NULL, [SearchResults] [real] NULL, [SearchSave] [real] NULL, [SearchDelete] [real] NULL, [SearchDetails] [real] NULL, [ClientAdd] [real] NULL, [CMALoad] [real] NULL, [CMASave] [real] NULL, [CMADelete] [real] NULL, [ClientDelete] [real] NULL, [Logout] [real] NULL, [SiteCode] [nvarchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NUL +L ) ON [PRIMARY]
Re^2: insert label into file
by grashoper (Monk) on Mar 23, 2009 at 19:59 UTC
    I am still not clear on what is meant by repeat values, since I will be using some form of loop to insert the values from the hash and could actually just clobber the old and insert the new on top if I have too, since each dataset would represent a single row of data.
      The concern was exactly the clobbering. If you don't care about clobbering repeat values, then all these admonitions are irrelevant.

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