Using Native Format to Import or Export Data
Native format is recommended when you bulk transfer data between multiple instances of Microsoft SQL Server using a data file that does not contain any extended/double-byte character set (DBCS) characters.
To bulk transfer data between multiple instances of SQL Server by using a data file that contains extended or DBCS characters, you should use the Unicode native format. For more information, see Using Unicode Native Format to Import or Export Data.
Native format maintains the native data types of a database. Native format is intended for high-speed data transfer of data between SQL Server tables. If you use a format file, the source and target tables do not need to be identical. The data transfer involves two steps:
- Bulk exporting the data from a source table into a data file
- Bulk importing the data from the data file into the target table
The use of native format between identical tables avoids unnecessary conversion of data types to and from character format, saving time and space. To achieve the optimum transfer rate, however, few checks are performed regarding data formatting. To prevent problems with the loaded data, see the following restrictions list.
To import data in native format successfully, ensure that:
The data file is in native format.
Either the target table must be compatible with the data file (having the correct number of columns, data type, length, NULL status, and so forth), or you must use a format file to map each field to its corresponding columns.
If you import data from a file that is mismatched with the target table, the import operation might succeed but the data values inserted into the target table are likely to be incorrect. This is because the data from the file is interpreted by using the format of the target table. Therefore, any mismatch results in the insertion of incorrect values. However, under no circumstances can such a mismatch cause logical or physical inconsistencies in the database.
For information on using format files, see Format Files for Importing or Exporting Data.
A successful import will not corrupt the target table.
How bcp Handles Data in Native Format
This section discusses special considerations for how the bcp utility exports and imports data in native format.
The bcp utility uses the SQL Server internal binary data format to write noncharacter data from a table to a data file.
char or varchar data
At the beginning of each char or varchar field, bcp adds the prefix length.
When native mode is used, by default, the bcp utility converts characters from SQL Server to OEM characters before it copies them to a data file. The bcp utility converts characters from a data file to ANSI characters before it bulk imports them into a SQL Server table. During these conversions, extended character data can be lost. For extended characters, either use Unicode native format or specify a code page. For more information about using a code page, see Copying Data Between Different Collations.
If sql_variant data is stored as a SQLVARIANT in a native-format data file, the data maintains all of its characteristics. The metadata that records the data type of each data value is stored along with the data value. This metadata is used to re-create the data value with the same data type in a destination sql_variant column.
If the data type of the destination column is not sql_variant, each data value is converted to the data type of the destination column, following the normal rules of implicit data conversion. If an error occurs during data conversion, the current batch is rolled back. Any char and varchar values that are transferred between sql_variant columns may have code page conversion issues. For more information, see Copying Data Between Different Collations.
For more information about data conversion, see Data Type Conversion (Database Engine).
Command Options for Native Format
You can import native format data into a table using bcp, BULK INSERT or INSERT ... SELECT * FROM OPENROWSET(BULK...). For a bcp command or BULK INSERT statement, you can specify the data format on the command line. For an INSERT ... SELECT * FROM OPENROWSET(BULK...) statement, you must specify the data format in a format file.
Native format is supported by the following command line options:
Causes the bcp utility to use the native data types of the data.1
Uses the native or wide native data types of the data. Note that DATAFILETYPE is not needed if a format file specifies the data types.
1 To load native (-n) data to a format compatible with earlier versions of SQL Server clients, use the -V switch. For more information, see Importing Native and Character Format Data from Earlier Versions of SQL Server.
Alternatively, you can specify formatting on a per-field basis in a format file. For more information, see Format Files for Importing or Exporting Data.
The following examples demonstrate how to bulk export native data using bcp and bulk import the same data using BULK INSERT.
The examples require that a table named myTestNativeData table be created in the AdventureWorks sample database under the dbo schema. Before you can run the examples, you must create this table. In SQL Server Management Studio Query Editor, execute:
USE AdventureWorks; GO CREATE TABLE myTestNativeData ( Col1 smallint, Col2 nvarchar(50), Col3 nvarchar(50) );
To populate this table and view the resulting contents execute the following statements:
INSERT INTO myTestNativeData(Col1,Col2,Col3) VALUES(1,'DataField2','DataField3'); INSERT INTO myTestNativeData(Col1,Col2,Col3) VALUES(2,'DataField2','DataField3'); GO SELECT Col1,Col2,Col3 FROM myTestNativeData
Using bcp to Bulk Export Native Data
To export data from the table to the data file, use bcp with the out option and the following qualifiers:
Specifies native data types.
Specifies that the bcp utility connects to SQL Server with a trusted connection using integrated security. If -T is not specified, you need to specify -U and -P to successfully log in.
The following example bulk exports data in native format from the
myTestNativeData table into a new data file named
myTestNativeData-n.Dat data file. At the Microsoft Windows command prompt, enter:
bcp AdventureWorks..myTestNativeData out C:\myTestNativeData-n.Dat -n -T
Using BULK INSERT to Bulk Import Native Data
The following example uses BULK INSERT to import the data in the
myTestNativeData-n.Dat data file into the
myTestNativeData table. In SQL Server Management Studio Query Editor, execute:
USE AdventureWorks; GO BULK INSERT myTestNativeData FROM 'C:\myTestNativeData-n.Dat' WITH (DATAFILETYPE='native'); GO SELECT Col1,Col2,Col3 FROM myTestNativeData GO