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How to rotate rows into columns in a table using T-SQL

I have a table named Table1 contains records like the following,

field name          data type          length
------------          -----------         --------
field1                 nvarchar           60
field2                 nvarchar           60
field3                 int                    4
field4                 datetime           8

How to create a new table using T-SQL with fields and types get from Table1 above.

Thanks in advance
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ihenry
Asked:
ihenry
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3 Solutions
 
ihenryAuthor Commented:
If possible without using cursor, please.
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Frostbyte_ZeroCommented:
TransactSQL does not have an option to transpose.

You could export the data to Excel and transpose each column into a row and then Import the data back. This could be done as long as you don't exceed the row or column limitations in Excel.

Other than that you must use a Cursor.
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ChrisFretwellCommented:
You can do this without a cursor, but it can be messy.

What exactly do you want your end table to look like? Just to be clear.

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ihenryAuthor Commented:
I want to have a table structure something like this

create table NewTable
(
      field1      nvarchar(60),
      field2      nvarchar(60),
      field3      int,
      field4      datetime
)

But is has to be dynamically, since the number of records in Table1 could increase or decrease.
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BulZeyECommented:

try:

create table #test (fieldname varchar(100), datatype varchar(100), length varchar(50))

insert into #test
(fieldname,datatype,length)
select 'field1',                 'nvarchar',           '60'
union all
select 'field2',                 'nvarchar',           '60'
union all
select 'field3',                 'int',                    '4'
union all
select 'field4',                 'datetime',           '8'

declare @SQLStatement      nvarchar(2000),
        @ColumnDefinition nvarchar(1000),
        @TableName        nvarchar(50)

set @TableName = 'ThisIsMyTableName'

select @SQLStatement = 'CREATE TABLE ' + @TableName + ' (**COLUMNDEFINITION**)'

select @ColumnDefinition = COALESCE(@ColumnDefinition + ',','')
       + FieldName
       + ' '
       + DataType
       + CASE
           WHEN DataType in ('VARCHAR','NVARCHAR','CHAR','NCHAR','FLOAT') -- THIS CAN BE ALTERED TO SUIT YOUR NEEDS
            AND Length IS NOT NULL THEN '(' + Length + ')'
           ELSE ''
         END
  FROM #TEST

drop table #test

SET @SQLStatement = REPLACE(@SQLStatement,'**COLUMNDEFINITION**',@ColumnDefinition)

EXEC(@SQLStatement)

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ChrisFretwellCommented:
Do you want to create a new table structure based on the values in the original table not populate a table with values in the original.

Thats not too hard. For this code, you will need to expand the case statement to format the data type correctly. I only used the ones in your example. But it should get you the idea. If you want to

declare @sql varchar(2000)

set @sql = 'create table newtable ('
select @sql = @sql  + char(13)+char(10)+ [field name] + ' ' + case when [data type] in ('int','datetime','smalldatetime') then [data type] else [data type] + '(' + convert(varchar(4),[length]) + ')' end + ','
from #table1

set @sql = @sql + ')'
set @sql = replace(@sql,',)',')')
print @sql
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ihenryAuthor Commented:
How messy the code would be look like? which one is better from performance benefit between using and not cursor?
I'll accept cursor if there's no other option.
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ChrisFretwellCommented:
I printed teh statement, you'll want to exec it
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ChrisFretwellCommented:
No need to a cursor, your question sounded a bit different from what you wanted, so I dont think its a problem.

In almost any case, you can write code without a cursor. Some may be easy to code, some not. But the performance with no cursor is almost always faster. (like my excessive use of almost?)
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Frostbyte_ZeroCommented:
If you are dealing with thousands of rows it will be messy.

But I have a solution. Use DTS ActiveX Scripting:

'**********************************************************************
'  Visual Basic ActiveX Script
'************************************************************************

Function Main()


      Dim ConnectString

      ' Build the Connection String
      ConnectString = "PROVIDER=SQLOLEDB"
      ConnectString = ConnectString & ";SERVER=yourserver"
      ConnectString = ConnectString & ";UID=yourid"
      ConnectString = ConnectString & ";PWD=yourpassword"
      ConnectString = ConnectString & ";DATABASE=yourdatabase"

      Dim con, cmd, rst
      Dim SQL

      SQL = "SELECT * FROM yourtable"

      Set con = CreateObject("ADODB.Connection")
      con.ConnectionString = ConnectString
      con.Open

      Set cmd = CreateObject("ADODB.Command")
      cmd.ActiveConnection = con
      cmd.CommandText = SQL
      cmd.CommandTimeout = 0

      Set rst = CreateObject("ADODB.Recordset")      
      rst.Open cmd      

      Dim DDL
                              
      If rst.BOF And rst.EOF Then

      Else


            DDL = "CREATE TABLE yournewtable("

            Do While Not rst.EOF                        

                  If rst(1) = "varchar" Or rst(1) = "nvarchar" or rst(1) = "char" Then

                  DDL = DDL & Trim(rst(0)) & " " & Trim(rst(1)) & "(" & Trim(rst(2)) & "), "

                  Else

                  DDL = DDL & Trim(rst(0)) & " " & Trim(rst(1)) & ", "

                  End If

                  rst.MoveNext

            Loop

            DDL = Mid( DDL, 1, Len( DDL) - 2)

            DDL = DDL & ")"

      End if

      ' Clean up variables.
      Set rst = Nothing
      Set cmd = Nothing
      Set con = Nothing

      MsgBox DDL

      Main = DTSTaskExecResult_Success
End Function

The DDL variable will contain the SQL to cxreate the table. Just pass it back to the command object to execute the command. Voila! Instant Table. I tested it and it works perfectly.
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ihenryAuthor Commented:
Hi all,

thanks for the code, i'm getting closer solving my problem. But it's leading me to one problem, though.

I'm able to execute this statement,
create table #temp1 (allow_Read int  default 0,allow_Add int  default 0,allow_Edit int  default 0,allow_Delete int  default 0 )
select * from #temp1
drop table #temp1


but i'm getting error "Invalid object name '#temp1'." when executing these lines:
declare @s nvarchar(4000)
set @s = 'create table #temp1 (allow_Read int  default 0,allow_Add int  default 0,allow_Edit int  default 0,allow_Delete int  default 0 )'
exec(@s)
select * from #temp1 --> at this line
drop table #temp1


If i change #temp1 to global temporary table ##temp1 it then works fine.
Any reason why to this problem?


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Frostbyte_ZeroCommented:
#temp1 = Session Dependent Temporary Table
after exec(@s) the session is terminated
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BulZeyECommented:
Yes, the temp table that you are creating is being created but falls out of scope after the exec concludes. Then you try to reference it but it is already gone.

The code I posted is a valid T-SQL solution, have you tested it?
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ihenryAuthor Commented:
Great, Thanks for all the help.
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