R help - Feb 2011 - Delete Comment Lines from SQL String as a Vector

Hi,
I tried to remove the text starts by "--" to the end of the line as
below


sql=c("-- This is a comment line",
         "select sysdate  -- This is a comment Text" ,
         " from dual ")
>sql
[1] "-- This is a comment line"
[2] "select sysdate  -- This is a comment Text"
[3] " from dual "


I try to have this
> sql
[1] "select sysdate "
[2] " from dual "

Thank You for your help,
Mai Dang

Mai -
> sql=c("-- This is a comment line",
+          "select sysdate  -- This is a comment Text" ,
+          " from dual ")
> use = sub('--.*$','',sql)
> use[use != '']
[1] "select sysdate  " " from dual "

Although to get it to print the way you listed, you need
to reduce the width of the line:
> options(width=20)
> use[use != '']
[1] "select sysdate  "
[2] " from dual "

 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu


On Tue, 22 Feb 2011, Mai Dang wrote:
> Hi,
> I tried to remove the text starts by "--" to the end of the line
as below
>
>
> sql=c("-- This is a comment line",
>         "select sysdate  -- This is a comment Text" ,
>         " from dual ")
>> sql
> [1] "-- This is a comment line"
> [2] "select sysdate  -- This is a comment Text"
> [3] " from dual "
>
>
> I try to have this
>> sql
> [1] "select sysdate "
> [2] " from dual "
>
> Thank You for your help,
> Mai Dang
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Here is the way I usually write my SQL:
> x <- c('
+ select comm, count(*)   -- count the number of comms
+    from myDF    -- this is the dataframe
+    group by comm  -- grouping argument
+ ')
> x  # as vector
[1] "\nselect comm, count(*)   -- count the number of comms\n   from
myDF    -- this is the dataframe\n   group by comm  -- grouping
argument\n"
> cat(x)  # nicely printed
select comm, count(*)   -- count the number of comms
   from myDF    -- this is the dataframe
   group by comm  -- grouping argument
> # remove comments
> y <- gsub("--[^\n]*", "", x)
> y
[1] "\nselect comm, count(*)   \n   from myDF    \n   group by comm 
\n"
> cat(y)
select comm, count(*)
   from myDF
   group by comm
>

On Mon, Feb 21, 2011 at 6:08 PM, Mai Dang <mdmining at gmail.com>
wrote:
> Hi,
> I tried to remove the text starts by "--" to the end of the line
as below
>
>
> sql=c("-- This is a comment line",
> ? ? ? ? "select sysdate ?-- This is a comment Text" ,
> ? ? ? ? " from dual ")
>>sql
> [1] "-- This is a comment line"
> [2] "select sysdate ?-- This is a comment Text"
> [3] " from dual "
>
>
> I try to have this
>> sql
> [1] "select sysdate "
> [2] " from dual "
>
> Thank You for your help,
> Mai Dang
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Data Munger Guru

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