In many database systems, CLOB (Character Large Object) and BLOB (Binary Large Object) data types are used to store large amounts of text and binary data respectively. These data types allow us to handle and manipulate huge amounts of data efficiently.
When it comes to loading data into CLOB and BLOB columns, SQL Loader is a powerful tool that can be used to perform high-speed loading of data into Oracle databases. SQL Loader is a command-line utility provided by Oracle that can be used to load data from external files into Oracle tables.
In this blog post, we will explore how to use SQL Loader to load data into CLOB and BLOB columns.
Prerequisites
Before we start, make sure you have the following prerequisites in place:
- An Oracle database installed and running
- SQL Loader installed on your machine (it comes bundled with Oracle database installations)
Step 1: Prepare the Control File
A control file is a plain text file that defines the format of the data in the input file and maps it to the columns in the target table. We need to create a control file specific to our requirements.
Here’s an example of a control file (my_control.ctl) for loading data into CLOB and BLOB columns:
LOAD DATA
INFILE 'my_data.csv'
APPEND INTO TABLE my_table
FIELDS TERMINATED BY ','
(
column1,
column2,
clob_column CHAR(4000) TERMINATED BY EOF,
blob_column LOBFILE(external_filename) TERMINATED BY EOF
)
In the control file, make sure to specify the file name (input file) using the INFILE directive and the target table name using the INTO TABLE directive. The APPEND keyword indicates that the data should be appended to the existing data in the table.
The clob_column is defined using the CHAR data type with a length of 4000, which is the maximum size of a CLOB in Oracle. The TERMINATED BY EOF clause indicates that the data for this column should be read until the end of the current record.
The blob_column uses the LOBFILE directive to specify the external file name that contains the binary data to be loaded. The TERMINATED BY EOF clause is used to load the entire content of the external file into the BLOB column.
Step 2: Prepare the Data File
Next, we need to prepare the data file that contains the actual data to be loaded into the CLOB and BLOB columns. In our example, we are using a CSV file (my_data.csv), but you can use any format supported by SQL Loader.
Make sure that the data in the file is properly formatted and matches the column definitions in the control file. For the CLOB column, ensure that the data does not exceed 4000 characters.
For the BLOB column, create a separate external file that contains the binary data to be loaded. This could be an image, video, or any binary file.
Step 3: Run SQL Loader
Once the control file and the data file are ready, we can use SQL Loader to load the data into the CLOB and BLOB columns. Open a command prompt or terminal and execute the following command:
sqlldr username/password control=my_control.ctl log=my_log.log
Replace username/password with your actual Oracle database credentials, my_control.ctl with the name of the control file, and my_log.log with the desired name for the log file.
SQL Loader will start reading the data from the data file and loading it into the CLOB and BLOB columns based on the instructions in the control file. The log file will provide information about the loading process, any errors encountered, and the final status.
Conclusion
Using SQL Loader, we can efficiently load data into CLOB and BLOB columns in Oracle databases. By properly preparing the control file and the data file, we can easily load large amounts of text and binary data with ease.
Make sure to test the loading process on a smaller dataset and review the log file for any potential errors or issues before loading the actual production data.
Happy loading!