I seem to have relatively easy question, but I have a little problem. I would like to iterr through the column prices in table products and then sum the prices.
I know an easy solution would be to change sql query -> sum(price), but in my exercise I need to avoid this solution.
import psycopg2
connection = psycopg2.connect(
host='host',
user='user',
password='password',
dbname='dbname',
)
cursor = connection.cursor()
sql = "select price from products"
cursor.execute(sql)
for price in cursor:
print(sum(price))
figured it out:
sum = 0
for price in cursor:
sum = sum + price[0]
print(sum)
You can iterate over the cursor directly:
column_sum = sum(row[0] for row in cursor)
Or you can use one of the various "fetch" methods to access the results and save them to a variable first.
Your cursor has 3 methods for fetching:
fetchone() returns a single row
fetchmany(n) returns a list of n many rows
fetchall() returns a list of all rows
results = cursor.fetchall()
column_sum = sum(row[0] for row in results)
Note that in all cases one row of data is a tuple. This is the case even if you're only selecting one column (a 1-tuple).
Related
I am using sqlite3 in python 3 I want to get only the updated data from the database. what I mean by that can be explained as follows: the database already has 2 rows of data and I add 2 more rows of data. How can I read only the updated rows instead of total rows
Note: indexing may not help here because the no of rows updating will change.
def read_all():
cur = con.cursor()
cur.execute("SELECT * FROM CVT")
rows = cur.fetchall()
# print(rows[-1])
assert cur.rowcount == len(rows)
lastrowids = range(cur.lastrowid - cur.rowcount + 1, cur.lastrowid + 1)
print(lastrowids)
If you insert rows "one by one" like that
cursor.execute('INSERT INTO foo (xxxx) VALUES (xxxx)')
You then can retrieve the last inserted rows id :
last_inserted_id = cursor.lastrowid
BUT it will work ONLY if you insert a single row with execute. It will return None if you try to use it after a executemany.
If you are trying to get multiple ids of rows that were inserted at the same time see that answer that may help you.
I have a SQL Server database that has a table that lists other tables along with some meta data on them. I can pull this out through Python into a List. What I want to do then though is query each table for the number of rows in it and then append the result into my list.
So for example, I run the first part of the script and I get a List of items, each one containing a list of 3 items (name,activity, Table Name). I then want to cycle through my list, pick up the third item, use it in my SQL query and then append the result into a 4th item in the list.
It starts off
[[table1, act1, Table_1],[table2, act2, Table_2],[table3, act3, Table_3]]
The second part, first takes Table_1, counts the rows and then appends it the list
[[table1, act1, Table_1,10],[table2, act2, Table_2],[table3, act3, Table_3]]
and then for list 2 etc
[[table1, act1, Table_1,10],[table2, act2, Table_2,16],[table3, act3, Table_3]]
Tried a few things but not got any further!
Thanks in advance.
import pyodbc
conn = pyodbc.connect(connetStr)
cursor = conn.cursor()
wffList=[]
cursor.execute('SELECT C_NAME,C_ACTIVE, C_TABLE_NAME from T_FORM_HEAD')
for row in cursor:
wffList.append(row)
for row in wffList:
tabName=row[2]
quer=('SELECT Count(*) FROM '+ tabName)
cursor.execute(quer)
rowCount=cursor.fetchone()
You can creat new list and append row with all four values
new_results = []
for row in wffList:
tabName = row[2]
quer = ('SELECT Count(*) FROM '+ tabName)
cursor.execute(quer)
rowCount = cursor.fetchone()
row.append(rowCount)
new_results.append(row)
print(new_results)
Or you can use enumerate to get row's number
for number, row in enumerate(wffList):
tabName = row[2]
quer = ('SELECT Count(*) FROM '+ tabName)
cursor.execute(quer)
rowCount = cursor.fetchone()
wffList[number].append(rowCount)
print(wfflist)
But probably you could also write one SQL query to get all at once.
But it could be to complex for me at this moment.
I got this code:
cursor.execute('SELECT nom FROM productes WHERE listacompra = 1')
producteslc = cursor.fetchone()
The problem is that when I do print producteslc, it returns (u'Natillas',), when the value on the SQL Database is just Natillas.
What could I do to have a variable with value = Natillas? I'm trying to do some stuff with split but I'm not able to do it at my own.
Thank you
The result of fetchone is a tuple of the values of one row.
Since you only fetch a single column, the result is a tuple singleton: (u'Natillas',)
To get the string:
producteslc = cursor.fetchone()[0]
See: Tuples and Sequences in the doc
EDIT
To fetch several rows, you can use fetchall() function:
rows = cursor.fetchall()
for row in rows:
print(row[0])
To print each name.
I have the data in pandas dataframe which I am storing in SQLITE database using Python. When I am trying to query the tables inside it, I am able to get the results but without the column names. Can someone please guide me.
sql_query = """Select date(report_date), insertion_order_id, sum(impressions), sum(clicks), (sum(clicks)+0.0)/sum(impressions)*100 as CTR
from RawDailySummaries
Group By report_date, insertion_order_id
Having report_date like '2014-08-12%' """
cursor.execute(sql_query)
query1 = cursor.fetchall()
for i in query1:
print i
Below is the output that I get
(u'2014-08-12', 10187, 2024, 8, 0.3952569169960474)
(u'2014-08-12', 12419, 15054, 176, 1.1691244851866613)
What do I need to do to display the results in a tabular form with column names
In DB-API 2.0 compliant clients, cursor.description is a sequence of 7-item sequences of the form (<name>, <type_code>, <display_size>, <internal_size>, <precision>, <scale>, <null_ok>), one for each column, as described here. Note description will be None if the result of the execute statement is empty.
If you want to create a list of the column names, you can use list comprehension like this: column_names = [i[0] for i in cursor.description] then do with them whatever you'd like.
Alternatively, you can set the row_factory parameter of the connection object to something that provides column names with the results. An example of a dictionary-based row factory for SQLite is found here, and you can see a discussion of the sqlite3.Row type below that.
Step 1: Select your engine like pyodbc, SQLAlchemy etc.
Step 2: Establish connection
cursor = connection.cursor()
Step 3: Execute SQL statement
cursor.execute("Select * from db.table where condition=1")
Step 4: Extract Header from connection variable description
headers = [i[0] for i in cursor.description]
print(headers)
Try Pandas .read_sql(), I can't check it right now but it should be something like:
pd.read_sql( Q , connection)
Here is a sample code using cx_Oracle, that should do what is expected:
import cx_Oracle
def test_oracle():
connection = cx_Oracle.connect('user', 'password', 'tns')
try:
cursor = connection.cursor()
cursor.execute('SELECT day_no,area_code ,start_date from dic.b_td_m_area where rownum<10')
#only print head
title = [i[0] for i in cursor.description]
print(title)
# column info
for x in cursor.description:
print(x)
finally:
cursor.close()
if __name__ == "__main__":
test_oracle();
I am having a hard time converting data. I select the data from my database, which is returned in tuple format. I try to convert them using list(), but all I get is a list of tuples. I am trying to compare them to integers which i receive from parsing my JSON. What would be the easiest way to convert and compare these two?
from DBConnection import db
import pymssql
from data import JsonParse
db.execute('select id from party where partyid = 1')
parse = JsonParse.Parse()
for row in cursor:
curList = list(cursor)
i = 0
for testData in parse:
print curList[i], testData['data']
i += 1
Output:
(6042,) 6042
(6043,) 6043
(6044,) 6044
(6045,) 6045
SQL results always come as rows, which are sequences of columns; this is true even if there is just one column in each row.
Next, you are executing the query on the db object (whatever that may be), but are iterating over the cursor; if this works at all is more down to luck. You'd normally execute a query on the cursor object.
If you expect just one row to be returned, you can use cursor.fetchone() to retrieve that one row. Your for row in cursor loop is actually skipping the first row.
You could use:
cursor = connection.cursor()
cursor.execute('select id from party where partyid = 1')
result = cursor.fetchone()[0]
to retrieve the first column of the first row, or you could use tuple assignment:
cursor = connection.cursor()
cursor.execute('select id from party where partyid = 1')
result, = cursor.fetchone()
If you do need to match against multiple rows, you could use a list comprehension to extract all those id columns:
cursor = connection.cursor()
cursor.execute('select id from party where partyid = 1')
result = [row[0] for row in cursor]
Now you have a list of id values.
Quick and dirty:
print curList[i][0], testData['data']
Or how about:
for db_tuple, json_int in zip(cursor, parse):
print db_tuple[0], json_int