Loading data into temporary staging tables using SQL Loader.

12 Oct 2023

In data warehousing and ETL (extract, transform, load) processes, it is common to use temporary staging tables to store data before it is transformed and loaded into the final destination tables. SQL Loader is a powerful tool that can be used to efficiently load data from external files into Oracle database tables, including temporary staging tables. In this blog post, we will walk through the process of loading data into temporary staging tables using SQL Loader.

Introduction
Prerequisites
Create Temporary Staging Tables
Create Control File
Load Data using SQL Loader
Conclusion

Introduction

SQL Loader is a utility provided by Oracle for loading data from external files into Oracle database tables. It performs highly efficient, high-performance data loads, making it an excellent choice for loading large volumes of data into temporary staging tables.

Prerequisites

Before we begin, make sure you have the following prerequisites in place:

A working Oracle database installation with SQL Loader utility.
Access to the database with necessary privileges to create tables and load data.

Create Temporary Staging Tables

First, we need to create the temporary staging tables where the data will be loaded. These tables should have the same structure as the final destination tables. You can use SQL statements or a GUI tool like Oracle SQL Developer to create the tables. Here’s an example of creating a temporary staging table named staging_table:

CREATE TABLE staging_table (
   column1 datatype,
   column2 datatype,
   ...
   columnN datatype
);

Create Control File

Next, we need to create a control file that specifies how SQL Loader should load the data into the temporary staging tables. The control file contains information such as the location of the data file, delimiter, format of the data, and target table name. Here’s an example of a control file named example.ctl:

LOAD DATA
INFILE 'data_file.csv'
APPEND
INTO TABLE staging_table
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
TRAILING NULLCOLS
(
  column1,
  column2,
  ...
  columnN
)

Make sure to modify the data_file.csv and staging_table names according to your requirements.

Load Data using SQL Loader

Once the temporary staging tables and control file are ready, we can use SQL Loader to load the data into the tables. Open a command prompt or terminal and navigate to the location of the control file. Assuming you have SQL Loader installed and properly configured, run the following command:

sqlldr username/password control=example.ctl

Replace username and password with your actual database credentials, and example.ctl with the name of your control file.

SQL Loader will read the data from the data file specified in the control file and load it into the temporary staging table. You will see the status of the loading process in the command prompt or terminal.

Conclusion

In this blog post, we have explored the process of loading data into temporary staging tables using SQL Loader. By following these steps, you can efficiently load large volumes of data from external files into your Oracle database, making it ready for further transformation and loading into the final destination tables.

#SQLLoader #DataLoading

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