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Sunday 9 July 2023

How to read data from an Oracle database table using PySpark

 from pyspark.sql import SparkSession

# Create a SparkSession

spark = SparkSession.builder \

    .appName("Oracle Connection") \

    .config("spark.jars.packages", "oracle:oracle-jdbc:8.2.0.0") \

    .getOrCreate()

# Define the connection properties

url = "jdbc:oracle:thin:@//hostname:port/service_name"

properties = {

    "user": "your_username",

    "password": "your_password"

}

# Read data from Oracle table

df = spark.read.jdbc(url=url, table="your_table_name", properties=properties)

# Display the dataframe

df.show()

# Perform further transformations or analysis on the dataframe as needed

# Stop the SparkSession

spark.stop()


In the code above, we create a SparkSession and provide the necessary Oracle JDBC driver dependency using the spark.jars.packages configuration. Make sure to replace the hostname, port, and service_name in the url variable with your actual Oracle database connection details.

Next, define the properties dictionary with your Oracle database credentials (user and password).

To read data from a specific table in the Oracle database, use the read.jdbc() method, passing the url, table, and properties as arguments.

After reading the data, you can perform further transformations or analysis on the resulting DataFrame object df. Finally, stop the SparkSession using spark.stop().

Ensure that you have the Oracle JDBC driver accessible to your PySpark environment by either providing the driver JAR file explicitly or using a package management system like Maven or Gradle.

You can apply filters while reading data from an Oracle table using PySpark. The read.jdbc() method in PySpark supports specifying a query as the table parameter, allowing you to apply filters directly in the SQL query. Here's an example:

from pyspark.sql import SparkSession

# Create a SparkSession
spark = SparkSession.builder \
    .appName("Oracle Connection") \
    .config("spark.jars.packages", "oracle:oracle-jdbc:8.2.0.0") \
    .getOrCreate()

# Define the connection properties
url = "jdbc:oracle:thin:@//hostname:port/service_name"
properties = {
    "user": "your_username",
    "password": "your_password"
}

# Define the filter condition
filter_condition = "column_name = 'value'"

# Read data from Oracle table with filter
query = f"(SELECT * FROM your_table_name WHERE {filter_condition}) AS filtered_table"
df = spark.read.jdbc(url=url, table=query, properties=properties)

# Display the dataframe
df.show()

# Perform further transformations or analysis on the dataframe as needed

# Stop the SparkSession
spark.stop()


Yes, you can apply filters while reading data from an Oracle table using PySpark. The read.jdbc() method in PySpark supports specifying a query as the table parameter, allowing you to apply filters directly in the SQL query. Here's an example:

python
Copy code
from pyspark.sql import SparkSession

# Create a SparkSession
spark = SparkSession.builder \
    .appName("Oracle Connection") \
    .config("spark.jars.packages", "oracle:oracle-jdbc:8.2.0.0") \
    .getOrCreate()

# Define the connection properties
url = "jdbc:oracle:thin:@//hostname:port/service_name"
properties = {
    "user": "your_username",
    "password": "your_password"
}

# Define the filter condition
filter_condition = "column_name = 'value'"

# Read data from Oracle table with filter
query = f"(SELECT * FROM your_table_name WHERE {filter_condition}) AS filtered_table"
df = spark.read.jdbc(url=url, table=query, properties=properties)

# Display the dataframe
df.show()

# Perform further transformations or analysis on the dataframe as needed

# Stop the SparkSession
spark.stop()
In the code above, we define a filter condition as filter_condition using the desired column name and value. We then construct a SQL query by incorporating the filter condition within a subquery.

The subquery is defined as (SELECT * FROM your_table_name WHERE {filter_condition}) AS filtered_table, where your_table_name is the name of the Oracle table you want to read from.

Pass the constructed query as the table parameter in the read.jdbc() method. This will read only the filtered data from the Oracle table into the DataFrame df.

After reading the filtered data, you can perform further transformations or analysis on the resulting DataFrame object df.

Remember to replace the hostname, port, service_name, your_username, your_password, column_name, and value with the appropriate values for your Oracle database and filtering requirements.