Using control files in SQL Loader.

12 Oct 2023

SQL Loader is a powerful tool for bulk loading data into Oracle databases. It allows you to load data from various file formats such as CSV, TXT, and DAT, and provides flexible options for data transformation and loading.

One of the key components of SQL Loader is the control file. A control file is a text file that specifies the details of the data to be loaded, such as the table name, column mappings, data format, and data transformations. In this blog post, we’ll explore how to use control files in SQL Loader to efficiently load data into an Oracle database.

Creating a Control File
Defining the Data Format
Specifying Column Mappings
Applying Data Transformations
Handling Errors and Rejections
Conclusion

Creating a Control File

To start using SQL Loader with control files, you need to create a control file that describes the structure of the data to be loaded. The control file is a simple text file with a specific format.

Here’s an example of a basic control file:

LOAD DATA
INFILE '/path/to/data.csv'
INTO TABLE my_table
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
(
  column1,
  column2,
  column3
)

In this example, we specify the input file using the INFILE keyword and specify the target table using the INTO TABLE keyword. We also define the field delimiter (FIELDS TERMINATED BY) and an optional text enclosure (OPTIONALLY ENCLOSED BY). Finally, we map the columns in the input file to the corresponding columns in the target table.

Defining the Data Format

When working with control files, it’s essential to define the data format correctly. You can specify the data types and lengths of each column using the appropriate syntax in the control file.

For example, if you have a column in your input file that represents a date, you can use the DATE keyword to specify the format:

column4 DATE "YYYY-MM-DD"

Similarly, if you want to load a decimal number, you can use the DECIMAL EXTERNAL keyword followed by the precision and scale:

column5 DECIMAL EXTERNAL (10,2)

By precisely defining the data format, you can ensure that the data is loaded correctly into your database.

Specifying Column Mappings

In a control file, you can specify the column mappings between the input file and the target table. This allows you to control how the data is loaded and which columns are populated.

Here’s an example of a control file with column mappings:

LOAD DATA
INFILE '/path/to/data.csv'
INTO TABLE my_table
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
(
  column1,
  column2,
  column3,
  column4 DATE "YYYY-MM-DD",
  column5 DECIMAL EXTERNAL (10,2)
)

In this example, we have mapped columns 1, 2, and 3 directly to columns in the my_table table. Additionally, we have defined custom mappings for columns 4 and 5, specifying their data types and formats.

Applying Data Transformations

SQL Loader provides various options for applying data transformations during the loading process. These transformations can be helpful in scenarios where you need to modify the data before inserting it into the database.

For example, you can use the CONCATENATE keyword to combine multiple input columns into a single target column:

column6 CHAR(10) "CONCATENATE(column1, column2)"

You can also use functions like TO_UPPER or TO_NUMBER to convert the case or data type of the input data before loading it into the database.

By utilizing these data transformation options, you can modify and format the data according to your requirements.

Handling Errors and Rejections

While loading data using SQL Loader, you may encounter errors or rejections due to data integrity issues or constraints violation. SQL Loader provides options for handling these errors and rejections gracefully.

One such option is the ERRORS parameter, which allows you to specify the number of errors to tolerate before stopping the loading process:

LOAD DATA
INFILE '/path/to/data.csv'
INTO TABLE my_table
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
ERRORS 100

In this example, the loading process will continue even if up to 100 errors are encountered. You can also redirect the rejected data to a separate file using the DISCARDFILE parameter.

Conclusion

Control files are a critical component of SQL Loader, enabling you to define the structure, format, and transformations of the data to be loaded into an Oracle database. By understanding how to create and use control files effectively, you can streamline the data loading process and ensure data integrity.

Remember to carefully define the data format, specify column mappings correctly, and apply data transformations as needed. Additionally, consider handling errors and rejections to maintain the quality and integrity of your data.

Start using control files in SQL Loader today to efficiently load and transform bulk data into your Oracle database!

#sqlloader #controlfiles

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