How to get a single result from a SQL query in python?

Question

Is there an elegant way of getting a single result from an SQLite SELECT query when using Python?

for example:

conn = sqlite3.connect('db_path.db')
cursor=conn.cursor()
cursor.execute("SELECT MAX(value) FROM table")

for row in cursor:
    for elem in row:
        maxVal = elem

is there a way to avoid those nested fors and get the value directly? I’ve tried

maxVal = cursor[0][0]

without any success.

Asked By: iliaden

||

Source

Answer 1

I think you’re looking for Cursor.fetchone() :

cursor.fetchone()[0]

Answered By: mouad

Answer 2

or you can try :
cursor.execute("SELECT * FROM table where name='martin'")

Answered By: WinuX

Answer 3

Or you could write a wrapper function that, given SQL, returns a scalar result:

def get_scalar_result(conn, sql):
    cursor=conn.cursor()
    cursor.execute(sql)

    return cursor.fetchone()[0]

I apologize for the possibly less than syntactically correct Python above, but I hope you get the idea.

Answered By: J. Polfer

Answer 4

If you’re not using pysqlite which has the built in cursor.fetchone

cursor.execute("select value from table order by value desc limit 1")

Answered By: user3467349

Answer 5

select count(*) from ... groupy by ... returns None instead of 0,
so fetchone()[0] would lead to an exception.

Therefore

def get_scalar_from_sql(sqlcur, sqlcmd):
    # select count(*) from .... groupy by ... returns None instead of 0
    sqlcur.execute(sqlcmd)
    scalar = 0
    tuple_or_None = sqlcur.fetchone()
    if not tuple_or_None is None:
        (scalar,) = tuple_or_None
    return scalar

Answered By: Markus

Answer 6

Sequence unpacking can be used to extract the scalar value from the result tuple.

By iterating over the cursor (or cursor.fetchall)if there are multiple rows:

for result, in cursor:
    print(result)

Or using cursor.fetchone if there is a single row in the resultset:

result, = cur.fetchone()
print(result)

In both cases the trailing comma after result unpacks the element from the single-element tuple. This is the same as the more commonly seen

a, b = (1, 2)

except the tuples only have one element:

a, = (1,)

Answered By: snakecharmerb

Answer 7

Be careful, accepted answer might cause TypeError!

Due to fetchone() documentation:

Fetches the next row of a query result set, returning a single sequence, or None when no more data is available.

So with some SQL queries cursor.fetchone()[0] could turn into None[0] which leads to raising TypeError exception.

Better way to get first row or None is:

first_row = next(cursor, [None])[0]

If SQL query is empty, next will use default value [None] and get first element from that list without raising exceptions.

Answered By: Alex Kosh

How to get a single result from a SQL query in python?

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