We Keep Coding

How to efficiently INSERT a dict whose keys match the table fields?

I very rarely use SQL with Python and recently needed to write some simple data in a table.
I use MariaDB but I think my question is relevant for other SQL based DBs.
I have a dict such as a = {'one": 1, 'two': 2 } that I need to INSERT into a table.
Following the documentation of the Python connector, I went for
cursor.execute(
"INSERT INTO mytable (one,two) VALUES (?, ?)",
(a['one'], b['two']))
Note that the names of the fields of the table correspond to the keys of the dict.
In reality, I had about 10 keys (which I still typed by hand the same way as above) but I could have ended up with a hundred.
Before I start to reinvent the wheel: is there a consensual way to insert such data into the DB?

Inserting arrays into databases

I am trying to write a general function that will insert a line of data into a table in a database but I am trying to write an array of unknown length. I am aiming to just be able to call this function in any programand write a line of data of any length to the table (assuming the table and the array are the same length.
I have tried adding the array like it is a singular peice of data.
import sqlite3
def add2Db(dbName, tableName, data):
connection = sqlite3.connect(dbName)
cur = connection.cursor()
cur.execute("INSERT INTO "+ tableName +" VALUES (?)", (data))
connection.commit()
connection.close()
add2Db("items.db", "allItems", (1, "chair", 5, 4))
This just crashes and gives me an error saying it has 4 columns but only one value was supplied.

SQLite does not support arrays - you have to convert to a TEXT using ','.join() to join your array items into a single string and pass that.
Source: SQLite website
https://www.sqlite.org/datatype3.html

I'm not a Python programmer, but I've been doing SQL a long time. I even wrote my own ORM. My advice is do not write your own SQL query builder. There's a myriad of subtle issues and especially security issues. I elaborate on a few of them below.
Instead, use a well-established SQL Query Builder or ORM. They've already dealt with these issues. Here's an example using SQLAlchemy.
from datetime import date
from sqlalchemy import create_engine, MetaData
# Connect to the database with debugging on.
engine = create_engine('sqlite:///test.sqlite', echo=True)
conn = engine.connect()
# Read the schemas from the database
meta = MetaData()
meta.reflect(bind=engine)
# INSERT INTO users (name, birthday, state, country) VALUES (?, ?, ?, ?)
users = meta.tables['users']
conn.execute(
users.insert().values(name="Yarrow Hock", birthday=date(1977, 1, 23), state="NY", country="US")
)
SQLAlchemy can do the entire range of SQL operations and will work with different SQL variants. You also get type safety.
conn.execute(
users.insert().values(name="Yarrow Hock", birthday="in the past", state="NY", country="US")
)
sqlalchemy.exc.StatementError: (exceptions.TypeError) SQLite Date type only accepts Python date objects as input. [SQL: u'INSERT INTO users (name, birthday, state, country) VALUES (?, ?, ?, ?)']
insert into table values (...) relies on column definition order
This relies on the order columns were defined in the schema. This leaves two problems. First is a readability problem.
add2Db(db, 'some_table', (1, 39, 99, 45, 'papa foxtrot', 0, 42, 0, 6)
What does any of that mean? A reader can't tell. They have to go digging into the schema and count columns to figure out what each value means.
Second is a maintenance problem. If, for any reason, the schema is altered and the column order is not exactly the same, this can lead to some extremely difficult to find bugs. For example...
create table users ( name text, birthday date, state text, country text );
vs
create table users ( name text, birthday date, country text, state text );
add2Db(db, 'users', ('Yarrow Hock', date(1977, 1, 23), 'NY', 'US'));
That insert will silently "work" with either column order.
You can fix this by passing in a dictionary and using the keys for column names.
add2Db(db, 'users', (name="Yarrow Hock", birthday=date(1977, 1, 23), state="NY", country="US"));
Then we'd produce a query like:
insert into users
(name, birthday, state, country)
values (?, ?, ?, ?)
This leads to the next and much bigger problem.
SQL Injection Attack
Now this opens up a new problem. If we simply stick the table and column names into the query that leaves us open to one of the most common security holes, a SQL Injection Attack. That's where someone can craft a value which when naively used in a SQL statement causes the query to do something else. Like Little Bobby Tables.
While the ? protects against SQL Injection for values, it's still possible to inject via the column names. There's no guarantee the column names can be trusted. Maybe they came from the parameters of a web form?
Protecting table and column names is complicated and easy to get wrong.
The more SQL you write the more likely you're vulnerable to an injection attack.
You have to write code for everything else.
Ok, you've done insert. Now update? select? Don't forget about subqueries, group by, unions, joins...
If you want to write a SQL query builder, cool! If, instead, you have a job to do using SQL, writing yet another SQL query builder is not your job.
It's harder for anyone else to understand.
There's a good chance that any given Python programmer knows how SQLAlchemy works, and there's plenty of tutorials and documentation if they don't. There's no chance they know about your home-rolled SQL functions, and you have to write all the tutorials and docs.

You shouldn't try to write your own ORMs without an argumented need. You will have a lot of problems, for example here's quick 25 reasons not to.
Instead use any popular orm that is proven. I recommend using SQLAlchemy as a go to outside of Django. Using it you can map a dict of values to insert it into a model just like insert(schema_name).values(**dict_name) (here's an example of insert/update).

Change your function to this:
def add2Db(dbName, tableName, data):
num_qs = len(data)
qm = ','.join(list('?' * num_qs))
query = """
INSERT INTO {table}
VALUES ({qms})
""".format(table=tableName,
qms=qm)
connection = sqlite3.connect(dbName)
cur = connection.cursor()
cur.execute(query, data)
connection.commit()
connection.close()

Insert list of values into postgres database [duplicate]

This question already has answers here:
imploding a list for use in a python MySQLDB IN clause
(8 answers)
Closed 1 year ago.
I want to insert a list in my database but I can't.
Here is an example of what I need:
variable_1 = "HELLO"
variable_2 = "ADIOS"
list = [variable_1,variable_2]
INSERT INTO table VALUES ('%s') % list
Can something like this be done? Can I insert a list as a value?
When I try it, an error says that is because of an error in MySQL syntax

The answer to your original question is: No, you can't insert a list like that.
However, with some tweaking, you could make that code work by using %r and passing in a tuple:
variable_1 = "HELLO"
variable_2 = "ADIOS"
varlist = [variable_1, variable_2]
print "INSERT INTO table VALUES %r;" % (tuple(varlist),)
Unfortunately, that style of variable insertion leaves your code vulnerable to SQL injection attacks.
Instead, we recommend using Python's DB API and building a customized query string with multiple question marks for the data to be inserted:
variable_1 = "HELLO"
variable_2 = "ADIOS"
varlist = [variable_1,variable_2]
var_string = ', '.join('?' * len(varlist))
query_string = 'INSERT INTO table VALUES (%s);' % var_string
cursor.execute(query_string, varlist)
The example at the beginning of the SQLite3 docs shows how to pass arguments using the question marks and it explains why they are necessary (essentially, it assures correct quoting of your variables).

Your question is not clear.
Do you want to insert the list as a comma-delimited text string into a single column in the database? Or do you want to insert each element into a separate column? Either is possible, but the technique is different.
Insert comma-delimited list into one column:
conn.execute('INSERT INTO table (ColName) VALUES (?);', [','.join(list)])
Insert into separate columns:
params = ['?' for item in list]
sql = 'INSERT INTO table (Col1, Col2. . .) VALUES (%s);' % ','.join(params)
conn.execute(sql, list)
both assuming you have established a connection name conn.
A few other suggestions:
Try to avoid INSERT statements that do not list the names and order of the columns you're inserting into. That kind of statement leads to very fragile code; it breaks if you add, delete, or move columns around in your table.
If you're inserting a comma-separted list into a single-field, that generally violates principals of database design and you should use a separate table with one value per record.
If you're inserting into separate fields and they have names like Word1 and Word2, that is likewise an indication that you should be using a separate table instead.
Never use direct string substitution to create SQL statements. It will break if one of the values is, for example o'clock. It also opens you to attacks by people using SQL injection techniques.

You can use json.dumps to convert a list to json and write the json to db.
For example:
insert table example_table(column_name) values(json.dumps(your_list))

dynamic table mysqldb python string/int issue

I am receiving an error when trying to write data to a database table when using a variable for the table name that I do not get when using a static name. For some reason on the line where I insert, if I insert an integer as the column values the code runs and the table is filled, however, if I try to use a string I get a SQL syntax error
cursor = db.cursor()
cursor.execute('DROP TABLE IF EXISTS %s' %data[1])
sql ="""CREATE TABLE %s (IP TEXT, AVAILIBILITY INT)""" %data[1]
cursor.execute(sql)
for key in data[0]:
cur_ip = key.split(".")[3]
cursor.execute("""INSERT INTO %s VALUES (%s,%s)""" %(data[1],key,data[0][key]))
db.commit()
the problem is where I have %(data[1], key, data[0][key]) any ideas?

It's a little hard to analyse your problem when you don't post the actual error, and since we have to guess what your data actually is. But some general points as advise:
Using a dynamic table name is often not way DB-systems want to be used. Try thinking if the problem could be used by using a static table name and adding an additional key column to your table. Into that field you can put what you did now as a dynamic table name. This way the DB might be able to better optimize your queries, and your queries are less likely to get errors (no need to create extra tables on the fly for once, which is not a cheap thing to do. Also you would not have a need for dynamic DROP TABLE queries, which could be a security risk.
So my advice to solve your problem would be to actually work around it by trying to get rid of dynamic table names altogether.
Another problem you have is that you are using python string formatting and not parameters to the query itself. That is a security problem in itself (SQL-Injections), but also is the problem of your syntax error. When you use numbers, your expression evaluates to
INSERT INTO table_name VALUES (100, 200)
Which is valid SQL. But with strings you get
INSERT INTO table_name VALUES (Some Text, some more text)
which is not valid (since you have no quotes ' around the strings.
To get rid of your syntax problem and of the sql-injection-problem, don't add the values to the string, pass them as a list to execute():
cursor.execute("INSERT INTO table_name VALUES (%s,%s)", (key, data[0][key]))
If you must have a dynamic table name, put that in your query string first (e.g. with % formatting), and give the actual values for your query as parameters as above (since I cannot imagine that execute will accept the table name as a parameter).
To put it in some simple sample code. Right now you are trying to do it like this:
# don't do this, this won't even work!
table_name = 'some_table'
user_name = 'Peter Smith'
user_age = 47
query = "INSERT INTO %s VALUES (%s, %s)" % (table_name, user_name, user_age)
cursor.execute(query)
That creates query
INSERT INTO some_table VALUES (Peter Smith, 100)
Which cannot work, because of the unquoted string. So you needed to do:
# DON'T DO THIS, it's bad!
query = "INSERT INTO %s VALUES ('%s', %s)" % (table_name, user_name, user_age)
That's not a good idea, because you need to know where to put quotes and where not (which you will mess up at some point). Even worse, imagine a user named named Connor O'Neal. You would get a syntax error:
INSERT INTO some_table VALUES ('Connor O'Neal', 100)
(This is also the way sql-injections are used to crush your system / steal your data). So you would also need to take care of escaping the values that are strings. Getting more complicated.
Leave those problems to python and mysql, by passing the date (not the table name) as arguments to execute!
table_name = 'some_table'
user_name = 'Peter Smith'
user_age = 47
query = "INSERT INTO " + table_name + " VALUES (%s, %s)"
cursor.execute(query, (user_name, user_age))
This way you can even pass datetime objects directly. There are other ways to put the data than using %s, take a look at this examples http://dev.mysql.com/doc/connector-python/en/connector-python-api-mysqlcursor-execute.html (that is python3 used there, I don't know which you use - but except of the print statements it should work with python2 as well, I think).

Inserting multiple strings into 1 table

I am trying to add 2 strings into a table.
My insert statement is:
INSERT INTO "State"
(state, relevant_id)
VALUES (%s, %s) """, state_values, relevant_id
This does not work because I am supplying too many arguments. Relevant_id is a variable that holds an integer, while state_values are values pertaining to the relevant_id.
Is there a way to insert both strings coming from 2 different variables? I am coding in python and using postgres as a db.

You should pass query parameters as a tuple in a second argument to execute:
cursor.execute("""INSERT INTO
State
(state, relevant_id)
VALUES
(%s, %s);""",
(state_values, relevant_id))
If you do it this way, you'll also get escaping to prevent sql injections for free.
Hope that helps.