Simplest way to insert variables into SQL Stored Procedure using Python? - sql

Question

I have a stored SQL procedure I would like to generalize. This involves passing the Table name, a start time, and an end time through as variables, so one doesn't have to edit the procedure every time. I'm trying to use basic python variables to prompt the user. (Start = int(input("Enter Start Time: "))
I just haven't found a simple way to do this. I've used 'execute sp_execute_external_scripts' and have been seeing if Pyodbc is the right tool for this, but nothing so far has worked, and I didn't fully understand the MS documentation/tutorial for creating a wrapper. So what is the easiest way to prompt the user for input that can be injected into a procedure as a variable? I feel like I'm missing something very simple here.
Upon reading comments here, my original method is overbroad and would require dynamicsql, which I'm not automatically opposed to, but it seems safer to create procedures for individual tables. So I should only need to push Start, End and ChunkSize as integer variables into the procedure.
SOLVED: I got the desired results by writing a small python program using pyodbc. Thank you for the help and gentle nudging away from my original, naive idea.
import pyodbc
connection = pyodbc.connect('Driver={SQL Server};'
'Server=CROWN;'
'Database=ControlInformation;'
'Trusted_Connection=yes;')
cursor = connection.cursor()
Start = int(input("Enter Start Time: "))
End = int(input("Enter End Time: "))
ChunkSize = int(input("Enter # of files to delete at once: "))
cursor.execute('exec PurgeCurrencyExchangeRates #start = %d, #end = %d,
#ChunkSize = %d' %(Start, End, ChunkSize))
cursor.commit(),
connection.close()
SQL stored procedure
CREATE PROCEDURE UserInput
#r int = 1,
#Start bigint = 0,
#End bigint = 0,
#TableName varchar(40) = 'CurrencyExchangeRates',
#ChunkSize int = 10000,
#ColumnName varchar(40) = 'Timestamp'
AS
BEGIN
SET NOCOUNT ON;
while #r > 0
delete top(#ChunkSize)
ControlInformation.dbo.#TableName
where #ColumnName > #Start and #ColumnName < #End
set #r = ##ROWCOUNT

Answer 1

The stored procedure should be something like:
use CurrencyExchangeRates
go
CREATE PROCEDURE PurgeCurrencyExchangeRates
#Start bigint = 0,
#End bigint = 0,
#ChunkSize int = 10000
AS
BEGIN
SET NOCOUNT ON;
declare #r int = 1;
while #r > 0
begin
delete top(#ChunkSize)
from dbo.CurrencyExchangeRates
where [Timestamp] >= #Start and [Timestamp] < #End
set #r = ##ROWCOUNT
end
end

Answer 2

Maybe you need in python:
Start = int(input("Enter Start Time: "))
sql = 'exec UserInput #start =?'
cursor.execute(sql, Start)
cursor.commit()

Answer 3

If you really want to make the table name dynamic then you'll need to use dynamic SQL, like so:
ALTER PROCEDURE DeleteFrom
#tableName sysname ='Table0'
AS
BEGIN
SET NOCOUNT ON;
DECLARE #sql nvarchar(4000);
SET #sql = N'DELETE TOP (1) FROM ' + QUOTENAME(#tableName);
EXEC(#sql);
END