Error with SQL string: "Error while connecting to PostgreSQL operator does not exist: date = integer"

Question

I have a Python(3) script that is supposed to run each morning. In it, I call some SQL. However I'm getting an error message:

Error while connecting to PostgreSQL operator does not exist: date = integer

The SQL is based on the concatenation of a string:

ecom_dashboard_query = """
with 
days_data as (
select 
    s.date,
    s.user_type,
    s.channel_grouping,
    s.device_category,
    sum(s.sessions) as sessions,
    count(distinct s.dimension2) as daily_users,
    sum(s.transactions) as transactions,
    sum(s.transaction_revenue) as revenue
from ga_flagship_ecom.sessions s
where date = """ + run.start_date + """
group by 1,2,3,4
)

insert into flagship_reporting.ecom_dashboard
select *
from days_data;
"""

Here is the full error:

09:31:25  Error while connecting to PostgreSQL  operator does not exist: date = integer
09:31:25  LINE 14: where date = 2020-01-19
09:31:25                      ^
09:31:25  HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.

I tried wrapping run.start_date within str like so: str(run.start_date) but I received the same error message.

I suspect it may be to do with the way I concatenate the SQL query string, but I am not sure.

The query runs fine in SQL directly with a hard coded date and no concatenation:

where date = '2020-01-19'

How can I get the query string to work correctly?

Answer 1

It's more better to pass query params to cursor.execute method. From docs

Warning Never, never, NEVER use Python string concatenation (+) or string parameters interpolation (%) to pass variables to a SQL query string. Not even at gunpoint.

So instead of string concatenation pass run.start_date as second argument of cursor.execute .

In your query instead of concatenation use %s :

where date = %s
group by 1,2,3,4

In your python code add second argument to execute method:

cur.execute(ecom_dashboard_query , (run.start_date,))

Answer 2

Your sentece is wrong:

where date = """ + run.start_date + """

try to compare a date and a string and this is not posible, you need to convert "run.start_date" to datetime and compare simply:

date_format = datetime.strptime(your_date_string, '%y-%m-%d')

and with this date converted to datetime do:

where date = date_format

Final code:

date_format = datetime.strptime(your_date_string, '%y-%m-%d')
ecom_dashboard_query = """
with 
days_data as (
select 
    s.date,
    s.user_type,
    s.channel_grouping,
    s.device_category,
    sum(s.sessions) as sessions,
    count(distinct s.dimension2) as daily_users,
    sum(s.transactions) as transactions,
    sum(s.transaction_revenue) as revenue
from ga_flagship_ecom.sessions s
where date = {}
group by 1,2,3,4
)

insert into flagship_reporting.ecom_dashboard
select *
from days_data;
""".format(date_format)