Dynamic SQL queries with SQLite3

Question

I would like to allow users to query a sql database.
The database is here

So the user will be able to enter the queries they want:

csr_city= input("Enter a city >>").lower().strip().replace(' ','')
csr_type = input("Enter a type >>").lower().strip()

and then the query will execute:

cur = conn.cursor()
cur.execute('SELECT * FROM crime_scene_report WHERE city=?  AND type=? ', (csr_city,csr_type))
rows = cur.fetchall()
rows

If the user enters both variables like city='SQL City' and type='murder' it works as it finds both values in the same row, but if the user leaves one empty, ex type, then it returns a blank table as both conditions do not exist on one single row.

What I would like to do is for SELECT to ignore the variable if it is empty.
I guess I could do it with if statements but that would create a mess?? Is there a better way?

I tried How to ignore the condition that user did not pass in SQLITE?, but didnt work for me, still getting empty tables.

Asked By: ruthpozuelo

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Source

Answer 1

You’re effectively looking for an SQL query builder (such as SQLAlchemy’s core layer), but to begin with, some ifs are just fine:

csr_city = input("Enter a city >>").lower().strip().replace(" ", "")
csr_type = input("Enter a type >>").lower().strip()

cur = conn.cursor()

sql_where = []
args = []
if csr_city:
    sql_where.append("city = ?")
    args.append(csr_city)
if csr_type:
    sql_where.append("type = ?")
    args.append(csr_type)

if not sql_where:
    sql_where.append("1 = 1")  # always true

sql_query = f'SELECT * FROM crime_scene_report WHERE {" AND ".join(sql_where)}'
cur.execute(sql_query, args)
rows = cur.fetchall()

Answered By: AKX

Dynamic SQL queries with SQLite3

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