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Posted Mar 26, 2007

SQL Server 2005 Integration Services - Part 45 - Bulk Insert Task and Format Files

By Marcin Policht

In the previous article of our series dealing with SQL Server 2005 Integration Services, we have presented a straightforward approach to importing data from delimited text files into database tables and views, using Bulk Insert Control Flow task (which, in turn, leverages T-SQL BULK INSERT functionality) with its basic formatting options. While such an approach might work well in some cases, its lack of flexibility is likely to become an issue (as was the case with our sample data file). One way to address such situations is to employ format files, which, while slightly more complex to implement, offer additional processing options. We will cover two types of such files, describing in more detail their characteristics and providing examples of their implementation.

We will demonstrate the use of format files by employing samples from our previous article, with the same target table that we have generated with Execute SQL Task containing the following SQLStatement property. (You might want to initiate for this purpose a new project of Integration Services type in the SQL Server 2005 Business Intelligence Studio or simply reuse the one we created as part of the exercise accompanying the previous article):

USE AdventureWorks;
IF EXISTS
   (SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
       WHERE TABLE_SCHEMA = 'HumanResources' 
   AND TABLE_NAME = 'myTeam')
    DROP TABLE HumanResources.myTeam
GO
CREATE TABLE HumanResources.myTeam 
(EmployeeID smallint NOT NULL,
Name nvarchar(50) NOT NULL,
Title nvarchar(50) NULL,
Background nvarchar(50) NOT NULL DEFAULT ''
);
GO

Our sample data file will also have the same content as before:

77,'Mia Doppleganger','Administrative Assistant','Microsoft Office'
49,'Hirum Mollicat','I.T. Specialist','Report Writing and Data Mining'

Which we pointed to using a Flat File Connection manager with Text qualifier set as a single quote (although as we have previously found out, this setting has no impact on the outcome of BULK INSERT operation).

Format files contain mapping instructions between data in a source file and columns in a target table. They can be applied to BULK INSERT, bpc, and INSERT ... SELECT * FROM OPENROWSET(BULK... statements (the last one actually requires their presence) in order to assist with more complex data import operations. Such operations might involve a mismatch (in terms of order or quantity) between data fields in a text file and columns in a target table (for example, when loading the same data file into multiple, distinct tables) or scenarios where delimiters differ across columns within the same data file. In general, there are two types of format files - XML-based ones (introduced with SQL Server 2005) and legacy ones (referred to as non-XML). Since both of them are compatible with SSIS Bulk Insert task, we will cover them here (they are interchangeable, although there are some exclusive benefits associated with each, which we will briefly mention).

Traditional format files follow syntactical rules presented in more detail in Understanding Non-XML Format Files article of SQL Server 2005 Books online. In particular, each starts with two rows that designate the format version number (9.0 indicates SQL Server 2005) and number of columns (corresponding to the number of relevant fields in the data file). These are followed by rows defining processing details for each of the target columns, including the position of each field in the data file, its datatype, prefix length (set to 0 if the field can contain NULL values), maximum data length (in bytes), field terminator, ordinal number of the corresponding column in a target table, column name, and its collation. While this might sound rather confusing and time-consuming to put together, you can easily generate such files with the bcp utility, by invoking it from the Command Prompt in the following manner (assuming that your target table already exists):

bcp targetTable format nul -c -t , -f formatFile.FMT -T

Where targetTable is name of the target table (AdventureWorks.HumanResources.myTeam in our case), format nul specifies the operation to be performed (i.e. generating a format file), -c indicates that the source file will be using character data type (other possible values -n, -N, and -w apply to native, widenative, and widechar data types, respectively), -T connects to SQL Server via integrated security (otherwise you need to specify login and password with -U and -P switches), -t , designates comma as the field delimiter (we keep the default of newline character as the row delimiter), and -f formatFile.FMT points to the format file that will contain the outcome of this operation (refer to the article on bcp Utility for a complete list of switches). In our case, the command will take the form:

bcp AdventureWorks.HumanResources.myTeam format nul -c -t , -f myTeam.Fmt -T

Which will result in the following non-XML format file (details might vary depending on your collation settings):

9.0
4
1 SQLCHAR 0 7 "," 1     EmployeeID ""
2 SQLCHAR 0 100 "," 2     Name SQL_Latin1_General_CP1_CI_AS
3 SQLCHAR 0 100 "," 3     Title SQL_Latin1_General_CP1_CI_AS
4 SQLCHAR 0 100 "\r\n" 4     Background SQL_Latin1_General_CP1_CI_AS

If we were to execute our sample SSIS Bulk Insert task with this format file, we would end up with the table content identical to the one presented in our previous article. In order to get rid of single quotes in the target table, we need to modify our format file and alter our delimiter definitions (which will populate the table with source data fields in the intended manner):

9.0
4
1 SQLCHAR 0 7 ",'" 1 EmployeeID ""
2 SQLCHAR 0 100 "','" 2 Name SQL_Latin1_General_CP1_CI_AS
3 SQLCHAR 0 100 "','" 3 Title SQL_Latin1_General_CP1_CI_AS
4 SQLCHAR 0 100 "'\r\n" 4 Background SQL_Latin1_General_CP1_CI_AS

Save these changes into a file residing in an arbitrary location on the SQL Server 2005 computer. To verify their correctness, add Bulk Insert task to the Control Flow Designer interface directly underneath the earlier configured Execute SQL task and make the former dependent on the success of the latter with a precedence constraint (or, if you are modifying the sample package created according to instructions in our previous article of this series, simply reuse the one already there). After displaying the task Editor window, ensure that its Connection subsection (within Connection section) points to the target server, database, and table ([AdventureWorks].[HumanResources].[myTeam]). In the Format subsection, point to the newly saved format file (with Format property set to "Use file"). Finally, ensure that our original text file is used as the Source Connection. Once you execute the package, the target table will be populated with data fields from our text file, but this time without extraneous delimiters.

The same goal can be accomplished with XML format files, which were introduced in SQL Server 2005. In addition to features available with their legacy counterparts, they give you the ability to identify not only data types of imported fields in a text file but also columns in a target table. Among their strengths are also self-documenting properties (which makes them easier to review and modify) and extensibility. On the other hand, they lack the ability to accommodate import scenarios, in which you need to skip one or more columns (except for the last one) in a target table. (To work around this limitation, you can create a view on the table and BULK INSERT into it). A detailed description of XML format file syntax is available in Schema Syntax for XML Format Files article of SQL Server 2005 Books Online. Just as with legacy format files, we can create an XML format file by leveraging the bcp utility. This is done by simply adding -x switch to the command line invocation we used previously and specifying myTeam.XML as the name of the format file to be created:

bcp AdventureWorks.HumanResources.myTeam format nul -c -t , -f myTeam.XML -x -T

Which will populate it with the following content:

<?xml version="1.0"?>
<BCPFORMAT xmlns="http://schemas.microsoft.com/sqlserver/2004/bulkload/format" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 <RECORD>
  <FIELD ID="1" xsi:type="CharTerm" TERMINATOR="," MAX_LENGTH="7"/>
  <FIELD ID="2" xsi:type="CharTerm" TERMINATOR="," MAX_LENGTH="100" COLLATION="SQL_Latin1_General_CP1_CI_AS"/>
  <FIELD ID="3" xsi:type="CharTerm" TERMINATOR="," MAX_LENGTH="100" COLLATION="SQL_Latin1_General_CP1_CI_AS"/>
  <FIELD ID="4" xsi:type="CharTerm" TERMINATOR="\r\n" MAX_LENGTH="100" COLLATION="SQL_Latin1_General_CP1_CI_AS"/>
 </RECORD>
 <ROW>
  <COLUMN SOURCE="1" NAME="EmployeeID" xsi:type="SQLSMALLINT"/>
  <COLUMN SOURCE="2" NAME="Name" xsi:type="SQLNVARCHAR"/>
  <COLUMN SOURCE="3" NAME="Title" xsi:type="SQLNVARCHAR"/>
  <COLUMN SOURCE="4" NAME="Background" xsi:type="SQLNVARCHAR"/>
 </ROW>
</BCPFORMAT>

As before, in order to eliminate superfluous single quotes, you need to modify delimiters (referenced here with the marker TERMINATOR) to match the changes we applied to non-XML format file. Once this is completed, simply specify the location and name of this file as the value of the FormatFile property in the Connection section of the Bulk Insert Task Editor window (with Format property set to "Use File") and execute the package. For more detailed information on this topic, refer to the set of MSDN articles in the section titled Format Files for Importing or Exporting Data.

» See All Articles by Columnist Marcin Policht



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