How can I clone an SQL Server database on the same server in SQL Server 2008 Express?

From SSMS :

1 - Backup original database to .BAK file (your_source_db -> Task -> Backup).

2 - Right clicking the "Databases" and 'Restore Database'

3 - Device > ... (button) > Add > select the your_source_db.bak

4 - In 'General' tab, in 'Destination' section, rename in 'Database' your_source_db to new_name_db

5 - In 'Files' tab, tick 'Relocate all files to folder',

• Rename in 'Restore As' column the two lignes to keep consistency with new_name_db (.mdf, _log.ldf)

6 - In 'Options' tab, in 'Restore options' section, tick two fist options ('Overwrite...', 'Preserve...') and for 'Recovery state' : 'RESTORE WITH RECOVERY'

• Make also sure that in 'Tail-Log backup' section options are unticked to avoid keeping source db in 'restoring state' !

Another way that does the trick by using import/export wizard, first create an empty database, then choose the source which is your server with the source database, and then in the destination choose the same server with the destination database (using the empty database you created at first), then hit finish

It will create all tables and transfer all the data into the new database,

You could just create a new database and then go to tasks, import data, and import all the data from the database you want to duplicate to the database you just created.

This program copies a database to the same server under a different name. I relied on examples given on this site with some improvements.

-- Copies a database to the same server
-- Copying the database is based on backing up the original database and restoring with a different name

DECLARE @sourceDb nvarchar(50);    
DECLARE @destDb nvarchar(50);
DECLARE @backupTempDir nvarchar(200)

SET @sourceDb =  N'Northwind'         -- The name of the source database
SET @destDb =    N'Northwind_copy'    -- The name of the target database
SET @backupTempDir = N'c:\temp'       -- The name of the temporary directory in which the temporary backup file will be saved
-- --------- ---

DECLARE @sourceDb_ROWS nvarchar(50);  
DECLARE @sourceDb_LOG nvarchar(50);
DECLARE @backupPath nvarchar(400); 
DECLARE @destMdf nvarchar(100);
DECLARE @destLdf nvarchar(100);
DECLARE @sqlServerDbFolder nvarchar(100);

Declare @Ret as int = -1
Declare @RetDescription nvarchar(200) = ''

-- Temporary backup file name
SET @backupPath = @backupTempDir+ '\TempDb_' + @sourceDb + '.bak'    

-- Finds the physical location of the files on the disk
set @sqlServerDbFolder = (SELECT top(1) physical_name as dir
                           FROM sys.master_files where DB_NAME(database_id) = @sourceDb  );

-- Clears the file name and leaves the directory name
set @sqlServerDbFolder = REVERSE(SUBSTRING(REVERSE(@sqlServerDbFolder), CHARINDEX('\', REVERSE(@sqlServerDbFolder)) + 1, LEN(@sqlServerDbFolder))) + '\'

-- Finds the logical name for the .mdf file
set @sourceDb_ROWS = (SELECT f.name LogicalName FROM sys.master_files f INNER JOIN sys.databases d ON d.database_id = f.database_id
                      where d.name = @sourceDb  and   f.type_desc = 'ROWS' )

-- Finds the logical name for the .ldf file
set @sourceDb_LOG = (SELECT f.name LogicalName FROM sys.master_files f INNER JOIN sys.databases d ON d.database_id = f.database_id
                      where d.name = @sourceDb  and   f.type_desc = 'LOG' )

-- Composes the names of the physical files for the new database  
SET @destMdf = @sqlServerDbFolder + @destDb + N'.mdf'
SET @destLdf = @sqlServerDbFolder + @destDb + N'_log' + N'.ldf'

-- If the source name is the same as the target name does not perform the operation
if @sourceDb <> @destDb      
    begin 

    -- Checks if the target database already exists
    IF Not EXISTS (SELECT name FROM master.dbo.sysdatabases WHERE name = @destDb)
    begin 
        -- Checks if the source database exists
        IF EXISTS (SELECT name FROM master.dbo.sysdatabases WHERE name = @sourceDb) and (@sqlServerDbFolder is not null)
        begin 

            -- Opens the permission to run xp_cmdshell
            EXEC master.dbo.sp_configure 'show advanced options', 1
            RECONFIGURE WITH OVERRIDE
            EXEC master.dbo.sp_configure 'xp_cmdshell', 1
            RECONFIGURE WITH OVERRIDE
         
            -- If the temporary backup directory does not exist it creates it
            declare @md as nvarchar(100) = N'if not exist ' + @backupTempDir + N' md ' +@backupTempDir  
            exec xp_cmdshell  @md,  no_output

            -- Creates a backup to the source database to the temporary file
            BACKUP DATABASE @sourceDb TO DISK = @backupPath 

            -- Restores the database with a new name
            RESTORE DATABASE @destDb FROM DISK = @backupPath
            WITH REPLACE, 
            MOVE @sourceDb_ROWS TO @destMdf, 
            MOVE @sourceDb_LOG TO  @destLdf

            -- Deletes the temporary backup file
            declare @del as varchar(100) = 'if exist ' + @backupPath +' del ' +@backupPath 
            exec xp_cmdshell  @del ,  no_output

            -- Close the permission to run xp_cmdshell
            EXEC master.dbo.sp_configure 'xp_cmdshell', 0
            RECONFIGURE WITH OVERRIDE
            EXEC master.dbo.sp_configure 'show advanced options', 0
            RECONFIGURE WITH OVERRIDE
         
            set @ret = 1
            set @RetDescription = 'The ' +@sourceDb + ' database was successfully copied to ' + @destDb 
        
        end
        else
        begin
          set @RetDescription = 'The source database '''+ @sourceDb + ''' is not exists.'
          set @ret = -3
        end

    end
    else
    begin
      set @RetDescription = 'The target database '''+ @destDb + ''' already exists.'
      set @ret = -4
    end
end
else
begin
  set @RetDescription = 'The target database ''' +@destDb + ''' and the source database '''+ @sourceDb + ''' have the same name.'
  set @ret = -5
end

select @ret as Ret, @RetDescription as RetDescription

<!doctype html>

<head>
    <title>Copy Database</title>
</head>

<body>
    
    <?php
    
    $servername = "localhost:xxxx";
    $user1 = "user1";
    $pw1 = "pw1";
    $db1 = "db1";
    
    $conn1 = new mysqli($servername,$user1,$pw1,$db1);
    
    if($conn1->connect_error) {
        die("Conn1 failed: " . $conn1->connect_error);
    }
    
    $user2 = "user2";
    $pw2 = "pw2";
    $db2 = "db2";
    
    $conn2 = new mysqli($servername,$user2,$pw2,$db2);
    
    if($conn2->connect_error) {
        die("Conn2 failed: " . $conn2->connect_error);
    }
    
    $sqlDB1 = "SELECT * FROM table1";
    $resultDB1 = $conn1->query($sqlDB1);
    
    if($resultDB1->num_rows > 0) {
        while($row = $resultDB1->fetch_assoc()) {
            $sqlDB2 = "INSERT INTO table2 (col1, col2) VALUES ('" . $row["tableRow1"] . "','" . $row["tableRow2"] . "')";
            $resultDB2 = $conn2->query($sqlDB2);
        }
    }else{
        echo "0 results";
    }
    
    $conn1->close();
    $conn2->close();
    
    ?>
    
</body>

If you are MS SQL 2014 and newer;

DBCC CLONEDATABASE (CurrentDBName, NewDBName)
GO

Details;