Performing conditional loading using SQL Loader.

12 Oct 2023

In data integration scenarios, it is common to encounter situations where conditional loading is required. That is, loading specific data based on certain conditions. In such cases, SQL Loader is a powerful tool that can be used to perform conditional loading effectively.

Introduction to SQL Loader

SQL Loader is a command-line tool provided by Oracle that is used to load data from flat files into Oracle database tables. It supports various loading methods, including direct path and conventional path loading. SQL Loader provides a flexible and efficient way to load large volumes of data quickly.

Conditional Loading with SQL Loader

To perform conditional loading using SQL Loader, we can utilize the control file provided to specify conditions for loading data. The control file is a declarative file that defines how data should be loaded into the database.

Here’s an example of a control file that performs conditional loading based on a specific condition:

LOAD DATA
INFILE 'data.txt'
INTO TABLE employees
WHEN (department_id = 10)
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
(
  employee_id,
  first_name,
  last_name,
  department_id
)

In the above example, the WHEN clause specifies the condition for loading the data. Only the records where the department_id is equal to 10 will be loaded into the employees table.

Advanced Conditional Loading Techniques

SQL Loader also provides additional features to perform advanced conditional loading:

1. Using CASE Expressions

LOAD DATA
INFILE 'data.txt'
INTO TABLE employees
WHEN (CASE WHEN department_id < 100 THEN 'Y' ELSE 'N' END = 'Y')
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
(
  employee_id,
  first_name,
  last_name,
  department_id
)

In this example, a CASE expression is used within the WHEN clause to define a condition based on a more complex logic. The records for which the department_id is less than 100 will be loaded.

2. Utilizing IF Statements

LOAD DATA
INFILE 'data.txt'
INTO TABLE employees
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
(
  employee_id,
  first_name,
  last_name,
  department_id
)
BEGINIF (department_id = 10)
  WHEN (1=1) -- Condition is always true
  CONTINUEIF (1=0) -- Rows are never discarded
ENDIF

In this example, an IF statement is used to control the loading process. If the department_id is 10, the loading process will continue, irrespective of any subsequent conditions.

Conclusion

By leveraging the features provided by SQL Loader, we can easily perform conditional loading based on specific criteria. This enables us to selectively load data into our database tables, providing greater flexibility and control over the loading process.

Using SQL Loader for conditional loading not only simplifies the data integration process but also ensures efficient execution, especially when dealing with large volumes of data.

#sqlloader #conditionalloading