I am trying to use cx_Oracle to query a table in oracle DB (version 11.2) and get rows with values in a column between a datetime range.
I have tried the following approaches:
Tried between clause as described here, but cursor gets 0 rows
parameters = (startDateTime, endDateTime)
query = "select * from employee where joining_date between :1 and :2"
cur = con.cursor()
cur.execute(query, parameters)
Tried the TO_DATE() function and Date'' qualifiers. Still no result for Between or >= operator. Noteworthy is that < operator works. I also got the same query and tried in a sql client, and the query returns results. Code:
#returns no rows:
query = "select * from employee where joining_date >= TO_DATE('" + startDateTime.strftime("%Y-%m-%d") + "','yyyy-mm-dd')"
cur = con.cursor()
cur.execute(query)
#tried following just to ensure that some query runs fine, it returns results:
query = query.replace(">=", "<")
cur.execute(query)
Any pointers about why the between and >= operators are failing for me? (my second approach was in line with the answer in Oracle date comparison in where clause but still doesn't work for me)
I am using python 3.4.3 and used cx_Oracle 5.3 and 5.2 with oracle client 11g on windows 7 machine
Assume that your employee table contains the field emp_id and the row with emp_id=1234567 should be retrieved by your query.
Make two copies of your a program that execute the following queries
query = "select to_char(:1,'YYYY-MM-DD HH24:MI:SS')||' >= '||to_char(joining_date,'YYYY-MM-DD HH24:MI:SS')||' >= '||to_char(:2,'YYYY-MM-DD HH24:MI:SS') resultstring from employee where emp_id=1234567"
and
query="select to_char(joining_date,'YYYY-MM-DD HH24:MI:SS')||' >= '||to_char(TO_DATE('" + startDateTime.strftime("%Y-%m-%d") + "','yyyy-mm-dd'),'YYYY-MM-DD HH24:MI:SS') resultstring from employee where emp_id=1234567"
Show us the code and the value of the column resultstring
You are constructing SQL queries as strings when you should be using parameterized queries. You can't use parameterization to substitute the comparison operators, but you should use it for the dates.
Also, note that the referenced answer uses the PostgreSQL parameterisation format, whereas Oracle requires you to use the ":name" format.
Related
I have the following SQL statement where i am reading the database to get the records for 1 day. Here is what i tried in pgAdmin console -
SELECT * FROM public.orders WHERE createdat >= now()::date AND type='t_order'
I want to convert this to the syntax of psycopg2but somehow it throws me errors -
Database connection failed due to invalid input syntax for type timestamp: "now()::date"
Here is what i am doing -
query = f"SELECT * FROM {table} WHERE (createdat>=%s AND type=%s)"
cur.execute(query, ("now()::date", "t_order"))
records = cur.fetchall()
Any help is deeply appreciated.
DO NOT use f strings. Use proper Parameter Passing
now()::date is better expressed as current_date. See Current Date/Time.
You want:
query = "SELECT * FROM public.orders WHERE (createdat>=current_date AND type=%s)"
cur.execute(query, ["t_order"])
If you want dynamic identifiers, table/column names then:
from psycopg2 import sql
query = sql.SQL("SELECT * FROM {} WHERE (createdat>=current_date AND type=%s)").format(sql.Identifier(table))
cur.execute(query, ["t_order"])
For more information see sql.
I wish to execute the statement to delete records from a postgresql table older than 45 days in my python script as below:
Consider only the code below:
import psycopg2
from datetime import datetime
cur = conn.cursor()
mpath = None
sql1 = cur.execute(
"Delete from table1 where mdatetime < datetime.today() - interval '45 days'")
This causes the following error:
psycopg2.errors.InvalidSchemaName: schema "datetime" does not exist
LINE 1: Delete from logsearch_maillogs2 where mdatetime <
datetime.t...
How do I exactly change the format or resolve this. Do I need to convert. Saw a few posts which say that postgresql DateTime doesn't exist in PostgreSQL etc, but didn't find exact code to resolve this issue. Please guide.
The query is running in Postgres not Python you need to use SQL timestamp function not Python ones if you are writing a hard coded string. So datetime.today() --> now() per Current Date/time.
sql1 = cur.execute(
"Delete from table1 where mdatetime < now() - interval '45 days'")
Or you need to use parameters per here Parameters to pass in a Python datetime if you want a dynamic query.
sql1 = cur.execute(
"Delete from table1 where mdatetime < %s - interval '45 days'", [datetime.today()])
I'm using nim and db_sqlite to fetch some rows with certain _ids from a database table. For example:
for row in db.fastRows("SELECT * FROM t WHERE _id IN (?, ?)", #["1", "2"]):
echo row
This works as expected, however, the sequence at the end is constructed dynamically at runtime, which means I need a variable amount of ? in the query. I end up creating a sequence with question marks, joining them, interpolating the string and turning it into a database query:
var qs : seq[string]
for id in ids:
qs.add("?")
let query_string = """SELECT * FROM t WHERE _id IN ($1)""" % join(qs, ",")
let query = SqlQuery(query_string)
for row in db.fastRows(query, ids):
echo row
Is there a better way to construct a select ... in query in nim? Ideally one with just one ? in the SqlQuery.
(For what it's worth, the current behavior is similar to other languages I've used)
you could do the replacement manually, here's one way using strformat and map
import strformat,db_sqlite,sequtils,strutils
#assuming ids is a seq[string] here
let query = sql(&"SELECT * FROM t WHERE _id IN ({ids.map(dbQuote).join(\",\")})")
for row in db.fastRows(query):
echo row
Sorry for this but I'm real new to sqlite: i've created a database from an excel sheet I had, and I can't seem to fetch the values of the column I need
query = """ SELECT GNCR from table"""
cur.execute(query)
This actually works, but
query = """ SELECT ? from table"""
cur.execute(query, my_tuple)
doesn't
Here's my code:
def print_col(to_print):
db = sqlite3.connect('my_database.db')
cur = db.cursor()
query = " SELECT ? FROM my_table "
cur.execute(query, to_print)
results = cur.fetchall()
print(results)
print_col(('GNCR',))
The result is:
[('GNCR',), ('GNCR',), ('GNCR',), ('GNCR',), [...]]
instead of the actual values
What's the problem ? I can't figure it out
the "?" character in query is used for parameter substitution. Sqlite will escape the parameter you passed and replace "?" with the send text. So in effect you query after parameter substitution will be SELECT 'GNCR' FROM my_table where GNCR will be treated as text so you will get the text for each row returned by you query instead of the value of that column.
Basically you should use the query parameter where you want to substitute the parameter with escaped string like in where clause. You can't use it for column name.
Anyone know of a handy function to search through column_names in Vertica? From the documentation, it seems like \d only queries table_names. I'm looking for something like MySQL's information_schema.columns, but can't find any information about a similar table of meta-data.
Thanks!
In 5.1 if you have enough permissions you can do
SELECT * FROM v_catalog.columns;
to access columns's info, for some things you'll need to join with
v_catalog.tables
The answer may differ depending on the version of Vertica you are using.
In the latest version, 5.1, there is a COLUMNS system table. Just from looking at the online documentation here seems to be the most useful columns with their types:
TABLE_SCHEMA VARCHAR
TABLE_NAME VARCHAR
DATA_TYPE VARCHAR
That should give you what you need. If your version doesn't have the system table, let me know what version you're running and I'll see what we can do.
Wrap this python script in a shell function and you'll be able to see all tables that contain any two columns:
import argparse
parser = argparse.ArgumentParser(description='Find Vertica attributes in tables')
parser.add_argument('names', metavar='N', type=str, nargs='+', help='attribute names')
args = parser.parse_args()
def vert_attributes(*names):
first_name = names[0].lower()
first = "select root.table_name, root.column_name from v_catalog.columns root "
last = " where root.column_name like '%s' " % first_name
names = names[1:]
if len(names) >= 1:
return first + " ".join([" inner join (select table_name from v_catalog.columns where column_name like '%s') q%s on root.table_name = q%s.table_name " % (name.lower(), index, index) for index,name in enumerate(names)]) + last
else:
return first + last
print nz_attributes(*tuple(args.names))