i've been trying to get some data from my db by using below code, but the code is not working. is there any mistake that i made in the code, if so how can i fix it.
NOTE: i took the below code from just a script not a django or flesk web app.
def db():
conn = psycopg2.connect(
"dbname=mydb user=postgres password=****** host=*.*.*.*")
cur = conn.cursor()
cur.execute("""SELECT * FROM MddPublisher""")
query_results = cur.fetchall()
print(query_results)
db()
ERROR: psycopg2.errors.UndefinedTable: relation "mddpublisher" does not exist LINE 1: SELECT * FROM MddPublisher
additionally,i want to show below code to prove that connection is ok. the problem is that i can't receive data from my db whenever i try to execute select command through python.
def print_tables():
conn = psycopg2.connect(
"dbname=mydb user=postgres password=***** host=*.*.*.*.*")
cur = conn.cursor()
cur.execute("""SELECT table_name FROM information_schema.tables
WHERE table_schema = 'public'""")
for table in cur.fetchall():
print(table)
print_tables()
OUTPUT:
('MddPublisher',)
This is probably an issue with case sensitivity. Postgresql names are usually normalized to lower case. However, when used inside double quotes, they keep their case. So, to access a table named MddPublisher you must write it like "MddPublisher".
All the gory details are in Section 4.1.1, Identifiers and Key Words in the Postgresql 14 docs.
Related
I have a following query:
cursor = connection.cursor()
query = """
SELECT *
FROM `my_database`.table_a
"""
result = cursor.execute(query)
which works as expected. But I need to change my_database in cursor.execute. I try:
cursor = connection.cursor()
query = """
SELECT *
FROM %s.table_a
"""
result = cursor.execute(query, ("my_database",))
which gives an error pymysql.err.ProgrammingError: (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''my_database'.table_a at line 2")
how can I insert database name in cursor.execute please?
It is not possible to bind a database name (or any other database object name) using a placeholder in a prepared statement. This would be, among other problems, a security risk. However, you might be able to use an f-string here instead:
cursor = connection.cursor()
db_name = "my_database"
query = f"""
SELECT *
FROM {db_name}.table_a
"""
result = cursor.execute(query)
It should also be mentioned that the above is only SQL injection safe if you are certain that the database name is not coming from outside your own application.
I have parameterized queries with f strings such that the queries will select some data from a series of tables and joins, and I want to insert the resulting set of data into another pre-created table (tables been designed to house these results).
Python executes the code but the query results never show up in my table.
Assuming target_table is already created in singlestore database:
qry_load = 'insert into target_table select * from some_tables'
conn = engine.connect()
trans = conn.begin()
try:
conn.execute(qry_load)
trans.commit()
except:
trans.rollback()
raise
The code executes and acts as if all is ok, but the data never shows up in the target table.
How do I see what singlestore is passing back to better debug what is happening within the database?
Just replace begin() with cursor() function:
conn = engine.connect()
trans = conn.cursor()
If not resolved
1- Verify structure of source and destination tables if they are same or not.
2- remove try ,except and rollback() block so you can know the actual error.
Ex.
qry_load = 'insert into target_table select * from some_tables'
conn = engine.connect()
trans = conn.cursor()
conn.execute(qry_load)
trans.commit()
I am creating a Python script to interact with schema permissions (and relative tables) on Redshift. As suggested in some other StackOverflow posts I am using psycopg2 library.
When I try to execute some simple SELECT FROM queries I have no problems: I can execute and see results with no issues.
Problem comes when for example I try to create a new schema or granting / revoking permissions. This kind of queries don't look like to produce any effect.
Here I show a very simple example in which I attempt to create a new schema:
conn_string = "dbname='{}' port='{}' host='{}' user='{}' password='{}'".format(DB_NAME, DB_PORT, DB_HOST, DB_USER, DB_PWD)
con = psycopg2.connect(conn_string)
sql = "CREATE SCHEMA new_schema"
cur = con.cursor()
cur.execute(sql)
But when I look into the Redshift DB I don't see any new schema called new_schema. Same behaviour happens when I try to run some permission grant / revoke query.
Anyone knows what is going on?
You have to commit the transaction.
con = psycopg2.connect(conn_string)
sql = "CREATE SCHEMA new_schema"
cur = con.cursor()
cur.execute(sql)
con.commit()
I'm using the Python package MySQLdb to fetch data from a MySQL database. However, I notice that I can't fetch the entirety of the data.
import MySQLdb
db = MySQLdb.connect(host=host, user=user, passwd=password)
cur = db.cursor()
query = "SELECT count(*) FROM table"
cur.execute(query)
This returns a number less than what I get if I execute the exact same query in MySQL Workbench. I've noticed that the data it doesn't return is the data that was inserted into the database most recently. Where am I going wrong?
You are not committing the inserted rows on the other connection.
I'm new to mySQL and Python.
I have code to insert data from Python into mySQL,
conn = MySQLdb.connect(host="localhost", user="root", passwd="kokoblack", db="mydb")
for i in range(0,len(allnames)):
try:
query = "INSERT INTO resumes (applicant, jobtitle, lastworkdate, lastupdate, url) values ("
query = query + "'"+allnames[i]+"'," +"'"+alltitles[i]+"',"+ "'"+alldates[i]+"'," + "'"+allupdates[i]+"'," + "'"+alllinks[i]+"')"
x = conn.cursor()
x.execute(query)
row = x.fetchall()
except:
print "error"
It seems to be working fine, because "error" never appears. Instead, many rows of "1L" appear in my Python shell. However, when I go to MySQL, the "resumes" table in "mydb" remains completely empty.
I have no idea what could be wrong, could it be that I am not connected to MySQL's server properly when I'm viewing the table in MySQL? Help please.
(I only use import MySQLdb, is that enough?)
use commit to commit the changes that you have done
MySQLdb has autocommit off by default, which may be confusing at first
You could do commit like this
conn.commit()
or
conn.autocommit(True) Right after the connection is created with the DB