python Postgresql CREATE DATABASE IF NOT EXISTS is error

Question

I tried to learn about postgresql using python. I want to create condition CREATE DATABASE IF NOT EXISTS, but I always get an error. The error is :

File "learn_postgres.py", line 27, in InitDatabase
cursor.execute("CREATE DATABASE IF NOT EXISTS python_db")
psycopg2.ProgrammingError: syntax error at or near "NOT"
LINE 1: CREATE DATABASE IF NOT EXISTS python_db

Asked By: Stefani Johnsson

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Source

Answer 1

You could query from pg_catalog.pg_database to check if the database is exist like this:

SELECT datname FROM pg_catalog.pg_database WHERE datname = 'python_db'

Then from here you can add the logic to create your db.

Answered By: Tiny.D

Answer 2

Postgres does not support the condition IF NOT EXISTS in the CREATE DATABASE clause, however, IF EXISTS is supported on DROP DATABASE

There are two options:

drop & recreate

cursor.execute('DROP DATABASE IF EXISTS python_db')
cursor.execute('CREATE DATABASE python_db')
# rest of the script

check the catalog first & branch the logic in python

cursor.execute("SELECT 1 FROM pg_catalog.pg_database WHERE datname = 'python_db'")
exists = cursor.fetchone()
if not exists:
    cursor.execute('CREATE DATABASE python_db')
# rest of the script

Answered By: Haleemur Ali

Answer 3

from psycopg2 import sql
from psycopg2.errors import DuplicateDatabase

...
conn.autocommit = True
cursor = conn.cursor()

try:
    cursor.execute(sql.SQL('CREATE DATABASE {}').format(sql.Identifier(DB_NAME)))
except DuplicateDatabase:
    pass

Answered By: Elijah

python Postgresql CREATE DATABASE IF NOT EXISTS is error

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