Psycopg2.programmingerror: no results to fetch

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psycopg2.ProgrammingError: no results to fetch

When using the psycopg2 library in Python to interact with a PostgreSQL database, there are cases where you might encounter the psycopg2.ProgrammingError: no results to fetch error. This error message is raised when you try to fetch data from a result set, but there are no more records to retrieve.

Let’s understand this error in more detail with an example:

# Import the psycopg2 library
import psycopg2

# Establish a connection to the PostgreSQL database
connection = psycopg2.connect(database="your_database_name", user="your_username", password="your_password", host="your_host", port="your_port")

# Create a cursor object
cursor = connection.cursor()

# Execute a SELECT query
cursor.execute("SELECT * FROM your_table")

# Fetch all the records from the result set
rows = cursor.fetchall()

# Iterate over the records
for row in rows:
    # Process each row

# Close the cursor and connection
cursor.close()
connection.close()

In the above example, we execute a SELECT query and try to fetch all the records from the result set using the fetchall() method. However, if the result set is empty or there are no more records to fetch, the psycopg2.ProgrammingError: no results to fetch error will be raised.

To handle this error, we can use a try-except block:

# Import the psycopg2 library
import psycopg2
from psycopg2 import ProgrammingError

# Establish a connection to the PostgreSQL database
connection = psycopg2.connect(database="your_database_name", user="your_username", password="your_password", host="your_host", port="your_port")

# Create a cursor object
cursor = connection.cursor()

try:
    # Execute a SELECT query
    cursor.execute("SELECT * FROM your_table")

    # Fetch all the records from the result set
    rows = cursor.fetchall()

    # Iterate over the records
    for row in rows:
        # Process each row

except ProgrammingError as error:
    print("Error: ", error)

# Close the cursor and connection
cursor.close()
connection.close()

In the above example, we catch the psycopg2.ProgrammingError exception using the except block, and print the error message. This way, we can handle the error gracefully and continue with the rest of our code.

To avoid this error, you can also check if there are any records to fetch before attempting to fetch them. One way to do this is by using the rowcount attribute of the cursor object, which gives the number of rows affected by the last command:

# Import the psycopg2 library
import psycopg2

# Establish a connection to the PostgreSQL database
connection = psycopg2.connect(database="your_database_name", user="your_username", password="your_password", host="your_host", port="your_port")

# Create a cursor object
cursor = connection.cursor()

# Execute a SELECT query
cursor.execute("SELECT * FROM your_table")

# Check if there are any records to fetch
if cursor.rowcount == 0:
    print("No records to fetch")
else:
    # Fetch all the records from the result set
    rows = cursor.fetchall()

    # Iterate over the records
    for row in rows:
        # Process each row

# Close the cursor and connection
cursor.close()
connection.close()

In the above example, we check if the rowcount attribute is equal to 0 before attempting to fetch the records. If it is 0, we print a message indicating that there are no records to fetch. Otherwise, we proceed with fetching and processing the records.

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