The BCPColFmt method is used to create a binding between BCP data file fields and SQL Server columns. It takes in the length, type, terminator, and prefix length of a column as parameters and sets each of these properties for individual fields.
If the user chooses interactive mode, this method is called twice; once to set the column format according to the default values (which are according to the type of the server column), and once to set the format according to the column type of the choice of the client chosen during interactive mode, for each column.
In non-interactive modes, it is called only once per column to set the type of each column to character or native type, and to set the column and row terminators.
The BCPColFmt method allows you to specify the user-file format for bulk copies. For bulk copy, a format contains the following parts:
A mapping from user-file fields to database columns.
The data type of each user-file field.
The length of the optional indicator for each field.
The maximum length of data per user-file field.
The optional terminating byte sequence for each field.
The length of the optional terminating byte sequence.
Each call to BCPColFmt specifies the format for one user-file field. For example, to change the default settings for three fields in a five-field user data file, first call BCPColumns(5), and then call BCPColFmt five times, with three of those calls setting your custom format. For the remaining two calls, set eUserDataType to BCP_TYPE_DEFAULT, and set cbIndicator, cbUserData, and cbUserDataTerm to 0, BCP_VARIABLE_LENGTH, and 0 respectively. This procedure copies all five columns, three with your customized format and two with the default format.
The IBCPSession::BCPColumns method must be called before any calls to BCPColFmt. You must call BCPColFmt once for each column in the user file. Calling BCPColFmt more than once for any user-file column causes an error.
You do not have to copy all of the data in a user file to a SQL Server table. To skip a column, specify the format of the data for the column setting the idxServerCol parameter to 0. In order to skip a field, you still need all the information for the method to work correctly.
The data type of field in the user's data file. The data types available are listed in the SQL Server Native Client header file (sqlncli.h) with BCP_TYPE_XXX format, for example, BCP_TYPE_SQLINT4. If the BCP_TYPE_DEFAULT value is specified, the provider tries to use the same type as the table or view column type. For bulk copy operations out of SQL Server and into a file when the eUserDataType argument is BCP_TYPE_SQLDECIMAL or BCP_TYPE_SQLNUMERIC:
If the source column is not decimal or numeric, the default precision and scale are used.
If the source column is decimal or numeric, the precision and scale of the source column are used.
Prefix length for the field. The default is BCP_PREFIX_DEFAULT. The valid lengths for the prefix are 0, 1, 2, 4 and 8. A prefix size of 8 is most commonly used to indicate that the field is chunked. This is used for efficiently bulk copying large value type columns.
The maximum length, in bytes, of this field's data in the user file, not including the length of any length indicator or terminator.
Setting cbUserData to BCP_LENGTH_NULL indicates that all values in the data file fields are, or should be set to NULL. Setting cbUserData to BCP_LENGTH_VARIABLE indicates that the system should determine the length of data for each field. For some fields, this could mean that a length/null indicator is generated to precede data on a copy from SQL Server, or that the indicator is expected in data copied to SQL Server.
For SQL Server character and binary data types, cbUserData can be BCP_LENGTH_VARIABLE, BCP_LENGTH_NULL, 0, or some positive value. If cbUserData is BCP_LENGTH_VARIABLE, the system uses either the length indicator, if present, or a terminator sequence to determine the length of the data. If both a length indicator and a terminator sequence are supplied, bulk copy uses the one that results in the least amount of data being copied. If cbUserData is BCP_LENGTH_VARIABLE, the data type is a SQL Server character or binary type, and if neither a length indicator nor a terminator sequence is specified, the system returns an error message.
If cbUserData is 0 or a positive value, the system uses cbUserData as the maximum data length. However, if, in addition to a positive cbUserData, a length indicator or terminator sequence is provided, the system determines the data length by using the method that results in the least amount of data being copied.
The cbUserData value represents the count of bytes of data. If character data is represented by Unicode wide characters, then a positive cbUserData parameter value represents the number of characters multiplied by the size, in bytes, of each character.
The terminator sequence to be used for the field. This parameter is useful mainly for character data types because all other types are of fixed length or, in the case of binary data, require an indicator of length to accurately record the number of bytes present.
To avoid terminating extracted data, or to indicate that data in a user file is not terminated, set this parameter to NULL.
If more than one means of specifying a user-file column length is used (such as a terminator and a length indicator, or a terminator and a maximum column length), bulk copy chooses the one that results in the least amount of data being copied.
The bulk copy API performs Unicode-to-MBCS character conversion as required. Care must be taken to ensure that both the terminator byte string and the length of the byte string are set correctly.
The length, in bytes, of the terminator sequence to be used for the column. If no terminator is present or desired in the data, set this value to 0.
The ordinal position of the column in the database table. The first column number is 1. The ordinal position of a column is reported by IColumnsInfo::GetColumnInfo or similar methods. If this value is 0, bulk copy ignores the field in the data file.