SQL Loader is a powerful tool that allows you to load data from external files into Oracle databases. While it provides a straightforward way to import data, it’s essential to handle errors and exceptions properly to ensure data integrity and avoid unexpected issues.
In this blog post, we will explore how to handle errors and exceptions in SQL Loader effectively.
Table of Contents
Error Handling in SQL Loader
SQL Loader provides several error handling mechanisms that you can use to deal with various types of errors during the loading process. Here are a few notable ones:
1. CONTINUE_LOAD
By default, SQL Loader terminates the loading process upon encountering an error. However, you can use the CONTINUE_LOAD parameter to instruct SQL Loader to continue processing even if errors occur. This allows you to load as much data as possible while capturing error information in the log file.
sqlldr userid=username/password control=example.ctl errors=0
In the above example, the errors=0 parameter ensures that no errors would cause SQL Loader to terminate the loading process.
2. SKIP
The SKIP parameter allows you to skip a specific number of records when an error occurs. This is useful when you encounter known data anomalies that can be safely ignored.
OPTIONS (SKIP=5)
LOAD DATA
INFILE 'data.csv'
In the above example, SQL Loader will skip the first 5 records from the data.csv file, assuming those records have known issues.
3. LOAD=MINIMUM
The LOAD=MINIMUM parameter is used to load a minimum number of records even if errors are encountered. This can be useful when dealing with large data sets where the majority of records are error-free.
OPTIONS (LOAD=1000)
LOAD DATA
INFILE 'data.csv'
In the above example, SQL Loader will attempt to load at least 1000 records from the data.csv file, even if errors occur.
Exception Handling in SQL Loader
In addition to error handling, SQL Loader also supports exception handling to control the flow of the loading process based on specific conditions. Here’s how you can use exception handling in SQL Loader:
1. WHEN
The WHEN clause allows you to specify conditions for which an exception should be raised. You can use this clause to define custom logic based on the input data.
OPTIONS (SKIP=5)
LOAD DATA
INFILE 'data.csv'
...
WHEN (1:5) = 'ERROR' CONTINUE
WHEN (1:5) = 'WARNING' CONTINUE
WHEN (1:5) = 'SKIP' CONTINUE
In the above example, SQL Loader will continue loading the data if the first five characters of a record match ‘ERROR’, ‘WARNING’, or ‘SKIP’.
2. INTO TABLE
The INTO TABLE clause is used to catch exceptions and redirect problematic records into a separate table. This allows you to isolate and address the problematic data after the loading process.
OPTIONS (SKIP=5)
LOAD DATA
INFILE 'data.csv'
...
INTO TABLE error_table
In the above example, records that encounter exceptions during the loading process will be redirected to the error_table instead of the main target table.
Conclusion
Effective error and exception handling in SQL Loader is crucial to ensure the reliable loading of data into Oracle databases. By using mechanisms like CONTINUE_LOAD, SKIP, LOAD=MINIMUM, WHEN, and INTO TABLE, you can handle errors gracefully and maintain data integrity.
Remember, it’s essential to review the log file generated by SQL Loader to identify and address any loading issues promptly. With proper error and exception handling, you can streamline the data loading process and minimize disruptions to your database operations.
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