Q. Could you please explain how to use the BCP format file?A. The BCP format file provides an alternative way to use the BCP utility and adds flexibility to the program. The following example of a format file illustrates the use of BCP on an ASCII data file BCP Format File --------------- 4.2 4 1 sybchar 0 12 "" 1 f_name 2 sybchar 0 15 "" 2 l_name 3 sybchar 0 15 "," 3 city 4 sybchar 0 2 "\r\n" 4 state where: Row Description --- ----------- 1 Indicates the version number of BCP. 2 Represents the number of fields in the data file. Column Description ------ ----------- 1 Designates the field number of the data file. 2 Indicates the data type that is stored in the particular field of the data file. For ASCII data files, use "sybchar"; and for native format data files, use the default data types. 3 Indicates the prefix length, which is used to provide the most compact file storage. For ASCII data files, use 0. 4 Represents the length of the particular data file field. 5 Represents the field terminator. Common field terminators are commas and end of line characters (\r\n). 6 Indicates the column number of the table in the SQL Server database. 7 Gives the name of the field taken from the SQL table. It is not necessary to use the actual name of the field. However, the only condition is that it cannot be blank.Q. What is the difference between data in ASCII format and data in native format, and how does the data format relate to BCP?A. The information in BCP data files can be stored in two ways: ASCII and native format. In ASCII data files, the information is stored as ASCII characters. This format is useful if the data will be used with another program, such as a spreadsheet, or if the data is to be uploaded to SQL Server from some other database. The BCP format file described in question 1 is an example of a format file that could be used to BCP ASCII data out of or into SQL Server. Note that all data types are defined to be "sybchar" and have a prefix length of 0. The SQL Server engine performs all the data type conversions. The native format file contains the data's "native" data types as defined in the SQL Server database. Native format proves to be most useful when information is to be BCP'd out of one SQL Server and into a different SQL Server. The use of the native format saves time by eliminating the unnecessary conversion of data types into and out of character format. The following is an example of a native format BCP format file: BCP Format File --------------- 4.2 5 1 sybchar 1 512 "" 1 discnttype 2 sybchar 1 512 "" 2 stor_id 3 sybint2 1 2 "" 3 lowqty 4 sybint2 1 2 "" 4 highqty 5 sybflt8 0 8 "" 5 discount This particular format file was created by BCP'ing data out of the "discount" table from the "pubs" database and taking all default values for the fields.Q. What is the proper way to use the field length column and the delimiter column? How can they work with or against each other?A. Data can be field delimited either by a character set or by a specified fixed length. It can also be delimited using a combination of both character set and fixed length. However, caution must be taken. The BCP utility will take the first form of the delimiter it finds. For example, if the field is comma delimited and all elements in the field have at least 10 characters, and the length is set at 8, BCP will copy only the first 8 characters of all elements in that field. This mistake will most likely result in an error message from BCP. It is easiest to use the default option of fixed-length terminators for native format files.Q. What is the best way to create a format file to BCP my ASCII data into SQL Server?A. To create a format file that is easily modified, start the BCP utility by using the following command line: bcp <db_name>.<owner>.<table> out <data_file> /S<server> /Usa /P<password> When you start the program, a series of questions is asked. Choose all the default options. When prompted to save the information in a BCP format file, press Y, then ENTER. Then edit the format file to have data types of "sybchar" and a prefix length of 0 (zero), and enter the proper length and/or field terminators. After this process is completed, run the BCP utility with the /f <bcp.fmt> option. This option tells BCP to use the specified BCP format file.Q. Now that I know the structure and usage of the BCP format file, how can I use it to ignore extra columns in my ASCII file?A. If you have a data file that contains more fields than the table on SQL Server, you can redirect these unneeded fields to a null field, as in the following example, where the user wants to copy in the fields "f_name", "l_name", and "state", but does not want to make use of the "city" field that exists in the data file. The following is an example of both the data file and the BCP format file: ASCII Data File --------------- Howard Jones San Jose,CA William Smith Seattle,WA Anthony Henry Portland,OR BCP Format File --------------- 4.2 4 1 sybchar 0 10 "" 2 f_name 2 sybchar 0 10 "" 1 l_name 3 sybchar 0 15 "," 0 city 4 sybchar 0 2 "\r\n" 3 state Please note that on the fifth line of the BCP format file, the SQL Server table field designation (column 6) is 0 and the table field name (column 7) still has some form of an entry. The use of 0 in column 6 will allow any information between column 20 and the comma in the data file to be placed in the null field device (the city fields). The use of column 7 is to avoid a BCP syntax error and is useful in self documentation.Q. What are the most common problems seen when using BCP? What are the symptoms? And how do you solve the problems?A. The most common problems users have when using BCP fall into the following categories: * Trying to load native format. Users often try to load an ASCII file using the SQL Server native format. This results in all the hexadecimal values of the ASCII file being misinterpreted. An "unexpected end of file" error message is very common in this instance. The proper way to load the ASCII file is to represent the fields as character strings and to let SQL Server perform the data conversion. * Using the default size of the data type. Using the default size can sometimes lead to the same error as above ("unexpected end of file"). This is most common with the SQL Server money and date data types. For example, if the user does not insert the entire date string, but only a fraction of the entire date (that is, mm/dd/yy with no time), the default size option reads 25 characters, the length of the date type. The solution is to use delimiters or a user-defined, fixed- length ASCII file. * Hidden characters in the data file. Often a hidden character in an ASCII data file can cause problems when the BCP command is used. This problem usually masks itself in an "unexpected null found" error. This character usually can be found at the bottom of the file. Many utilities display hidden characters; finding and removing this hidden character should resolve the problem. * Using spaces for delimiters in a data file. Using the BCP command with the format file on a data file delimited with spaces returns the following error message "dblib error: column number out of range." To avoid this problem, run BCP without a format file by using the -t option on the command line. For example: bcp dbase..table out file.out -SServer -Usa -P -r\r\n -c -t" "
ID Bài viết: 67409 - Xem lại Lần cuối: 08/17/2011 14:22:00 - Bản sửa đổi: 2.0