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Create dynamic 'Create Table' statement

Posted on 2012-04-13
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Last Modified: 2012-04-13
Hello,
I have this logic below where it gets the columns from a table - 'Proc_Layouts' and there is a while loop that puts these columns together, and at the end, uses these columns to create a table.
I had it working one time, where it did select the columns and create the string - 'col1 varchar(10), col2 varchar(20), col3(varchar2), .....)
But when I added the last statement - 'Create table ' +
It doesn't even print it or retrieve the columns.  Am I out of scope somewhere or is there a better way to write this.
The 'Print @pSQL' statement doesn't seem to work and the result or message page just shows:
'(42 row(s) affected)'
Not showing the DDL statement that is supposed to be shown.
Thanks,
Steve

  Declare @pSQL    varchar(8000)  
, @pTypeKey   int  
, @pEXTColumns    varchar(8000)  
, @FieldOrder   int  
, @ColumnName   varchar(80)  
, @CurrentVariable  Varchar(10)  
, @FieldLength   varchar(4)
,@ud_ext_temp_table varchar(40)

  Set @pTypeKey = 1711
  Set @ud_ext_temp_table = 'My_EXT_Table'
 
 Declare @columns table  
   (  
    FieldOrder int,  
    columnname varchar(80),  
    fieldlength varchar(5)  
   )  
 
   Insert Into @columns (FieldOrder, ColumnName, FieldLength)  
   Select FieldOrder, fieldname, fieldlength  
   From proc_Layouts  
   Where  LayoutKey = @pTypeKey  
 
   Set @FieldOrder = (Select Min(FieldOrder) From @columns)  
 
   While @FieldOrder Is Not Null  
      Begin  
      Select      @ColumnName  = IsNull(columnname,'colxxx'),
            @FieldLength = IsNull(FieldLength, '80')
      From      @columns  
      Where      FieldOrder = @FieldOrder  
             
      Set @pEXTColumns = @pEXTColumns + ', '+@ColumnName+ ' VarChar(' + @FieldLength + ') '  
             
      Set @FieldOrder = (Select Min(fieldorder) From @columns Where fieldorder > @fieldorder)  

      End  
Set @pEXTColumns = right(@pEXTColumns, len(@pEXTColumns)) -- remove the first character (comma) of this string..  

set @pSQL = 'Create Table ' + @ud_ext_temp_table + ' (' + @pEXTColumns + ')'

print @pSQL
0
Comment
Question by:Machinegunner
6 Comments
 
LVL 14

Expert Comment

by:nishant joshi
ID: 37844133
might you are having an end less while loop try to print in while loop and check.

Regards,
0
 
LVL 40

Expert Comment

by:Kyle Abrahams
ID: 37844157
can you select @pSQL . .. does that return anything?
0
 

Author Comment

by:Machinegunner
ID: 37844427
Thanks for the replies, the @pSQL is coming back as NULL, when I do a 'Select @pSQL' and looks like some kind of endless loop somewhere?
Should I reinitialize @FieldOrder somewhere or another variable, to kick it out of the endless loop?
Thanks,
Steve
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LVL 18

Accepted Solution

by:
vasto earned 500 total points
ID: 37844461
Your @pEXTColumns variable has value null and since there is no place where this value is initialized
Set @pEXTColumns = @pEXTColumns + ', '+@ColumnName+ ' VarChar(' + @FieldLength + ') '  
will always set the value to null

add
set @pEXTColumns=''
somewhere at the beginning of the script ( for example after Set @pTypeKey = 1711)
0
 
LVL 18

Expert Comment

by:vasto
ID: 37844495
also you don't need cursor and temp table . try this code intead:

Declare @pSQL varchar(8000), @pTypeKey int, @ud_ext_temp_table varchar(40)
SELECT @pTypeKey = 1711, @ud_ext_temp_table = 'My_EXT_Table'

SELECT @pSQL = isnull(@pSQL + ',' ,'') + '[' +fieldname + '] VarChar(' + fieldlength  + ') '
FROM proc_Layouts  
WHERE  LayoutKey = @pTypeKey  
ORDER BY fieldorder

SET @pSQL = 'Create Table ' + @ud_ext_temp_table + ' (' + @pSQL + ')'
print @pSQL
0
 

Author Closing Comment

by:Machinegunner
ID: 37845177
Thanks for the solution as the setting of the @pEXTColumns = '' in the beginning, worked and created the DDL statement just fine.
Thanks also for the other logic, for creating without a cursor.
Much appreciated!
Thanks,
Steve
0

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