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Alter query according to user selection in sqlite python

I have a sqlite database named StudentDB which has 3 columns Roll number, Name, Marks. Now I want to fetch only the columns that user selects in the IDE. User can select one column or two or all the three. How can I alter the query accordingly using Python?
I tried:
import sqlite3
sel={"Roll Number":12}
query = 'select * from StudentDB Where({seq})'.format(seq=','.join(['?']*len(sel))),[i for k,i in sel.items()]
con = sqlite3.connect(database)
cur = con.cursor()
cur.execute(query)
all_data = cur.fetchall()
all_data
I am getting:
operation parameter must be str

You should control the text of the query. The where clause shall allways be in the form WHERE colname=value [AND colname2=...] or (better) WHERE colname=? [AND ...] if you want to build a parameterized query.
So you want:
query = 'select * from StudentDB Where ' + ' AND '.join('"{}"=?'.format(col)
for col in sel.keys())
...
cur.execute(query, tuple(sel.values()))

In your code, the query is now a tuple instead of str and that is why the error.
I assume you want to execute a query like below -
select * from StudentDB Where "Roll number"=?
Then you can change the sql query like this (assuming you want and and not or) -
query = "select * from StudentDB Where {seq}".format(seq=" and ".join('"{}"=?'.format(k) for k in sel.keys()))
and execute the query like -
cur.execute(query, tuple(sel.values()))
Please make sure in your code the provided database is defined and contains the database name and studentDB is indeed the table name and not database name.

python sqlite query selecting text padded with multiple zeros

I had trouble with selecting TEXT data type padded with zeros in front.
Found out there's something wrong with my DB.
My multiple tries and all of answers by peers should all should work.
Thanks #snakecharmerb and #forpas for pointing out for possible flaw in DB.
For example, code column includes
000001, 000010, 000300 ...
There are also a multiple of Data with same code.
code date
000030 20210101
000030 20210102
000030 20210103
000030 20210104
000030 20210105
...
I need to loop through a list so I tried multiple ways of using f-string, but it did not work.
con = sqlite3.connect("DIRECTORY")
cur = con.cursor()
code = '000030' // does not work
code = 000030 // forbidden by python 3.7
query = cur.execute(f"SELECT * From TABLE where code is {code}") // should work
query = cur.execute(f"SELECT * From TABLE where code is '{code}'") // should work
query = cur.execute(f'SELECT * From TABLE where code is "{code}"') // should work
query = cur.execute('SELECT * From TABLE where code = ?',('000030',)) // should work
query = cur.execute("SELECT * From TABLE where code is 000030") // works but cannot loop through a list
Also tried replacing 'is' with '=', '=='. All should work.

Whatever the data type of the column code is, this query should work:
query = cur.execute("SELECT * From TABLE where code = ?", ("000030",))
Try with implicit conversions to integers for the column value and the parameter that you pass:
query = cur.execute("SELECT * From TABLE where code + 0 = ? + 0", ("000030",))
If this does not work, it means that the values of the column code are not like the ones that you posted in your question.

Here's an working example:
import sqlite3
conn = sqlite3.connect(':memory:')
cur = conn.cursor()
cur.execute("""CREATE TABLE test (code TEXT)""")
for i in range(0, 100, 10):
cur.execute("""INSERT INTO test (code) VALUES (?)""", (str(i).zfill(5),))
conn.commit()
cur.execute("""SELECT * FROM test""")
for row in cur:
print(row)
print()
cur.execute("""SELECT code FROM test WHERE code = ?""", ('00030',))
for row in cur:
print(row)
print()
conn.close()
Output
('00000',)
('00010',)
('00020',)
('00030',)
('00040',)
('00050',)
('00060',)
('00070',)
('00080',)
('00090',)
('00030',)

python - SQL Select Conditional statements in python

This is my R piece of code but i want to do the same thing in python, as i am new in it having problems to write the correct code can anybody guide me how to write this is python. I have already made connections of database and also tried simple queries but here i am struggling
sql_command <- "SELECT COUNT(DISTINCT Id) FROM \"Bowlers\";"
total<-as.numeric(dbGetQuery(con, sql_command))
data<-setNames(data.frame(matrix(ncol=8,
nrow=total)),c("Name","Wkts","Ave","Econ","SR","WicketTaker","totalovers",
"Matches"))
for (i in 1:total){
sql_command <- paste("SELECT * FROM \"Bowlers\" where Id = ", i ,";",
sep="")
p<-dbGetQuery(con, sql_command)
p[is.na(p)] <- 0
data$Name[i] = p$bowler[1]
}
after this which works fine how should i proceed to write the loop code:
with engine.connect() as con:
rs=con.execute('SELECT COUNT(DISTINCT id) FROM "Bowlers"')
for row in rs:
print (row)

Use the format method for strings in python to achieve it.
I am using postgresql, but your connection should be similar. Something like:
connect to test database:
import psycopg2
con = psycopg2.connect("dbname='test' user='your_user' host='your_host' password='your_password'")
cur = con.cursor() # cursor method may differ for your connection
loop over your id's:
for i in range(1,total+1):
sql_command = 'SELECT * FROM "Bowlers" WHERE id = {}'.format(i)
cur.execute(sql_command) # execute and fetchall method may differ
rows = cur.fetchall() # check for your connection
print ("output first row for id = {}".format(i))
print (rows[0]) # sanity check, printing first row for ids
print('\n') # rows is a list of tuples
# you can convert them into numpy arrays

How to get table column-name/header for SQL query in python

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();

Select query in pymysql

When executing the following:
import pymysql
db = pymysql.connect(host='localhost', port=3306, user='root')
cur = db.cursor()
print(cur.execute("SELECT ParentGuardianID FROM ParentGuardianInformation WHERE UserID ='" + UserID + "'"))
The output is1
How could I alter the code so that the actual value of the ParentGuardianID (which is '001') is printed as opposed to 1.
I'm sure the answer is simple but I am a beginner so any help would be much appreciated - thanks!

cur.execute() just returns the number of rows affected. You should do cur.fetchone() to get the actual result, or cur.fetchall() if you are expecting multiple rows.

The cursor.execute() method gives out a cursor related to the result of the SQL sentence. In case of a select query, it returns the rows (if any) that meet it. So, you can iterate over these rows using a for loop for instance. In addition, I would recommend you to use pymysql.cursors.DictCursor because it allows treating the query results as a dictionary.
import pymysql
db = pymysql.connect(host='localhost', port=3306, user='root')
cur = db.cursor(pymysql.cursors.DictCursor)
UserId = 'whatsoever'
sql = "SELECT ParentGuardianID FROM ParentGuardianInformation WHERE UserID ='%s'"
cur.execute(sql % UserId)
for row in cur:
print(row['ParentGuardianID'])
Good luck!