Develop Reference

Creating a table in MariaDB using a list of column names in Python

I am trying to create a table in mariadb using python. I have all the column names stored in a list as shown below.
collist = ['RR', 'ABPm', 'ABPs', 'ABPd', 'HR', 'SPO']
This is just the sample list. Actual list has 200 items in the list. I am trying to create a table using the above collist elements as columns and the datatype for the columns is VARCHAR.
This is the code I am using to create a table
for p in collist:
cur.execute('CREATE TABLE IF NOT EXISTS table1 ({} VARCHAR(45))'.format(p)
The above code is executing but only the first element of the list is being added as a column in the table and I cannot see the remaining elements. I'd really appreciate if I can get a help with this.

You can build the string in 3 parts and then .join() those together. The middle portion is the column definitions, joining each of the item in the original list. This doesn't seem particularly healthy; both in the number of columns and the fact that everything is VARCHAR(45) but that's your decision:
collist = ['RR', 'ABPm', 'ABPs', 'ABPd', 'HR', 'SPO']
query = ''.join(["(CREATE TABLE IF NOT EXISTS table1 ",
' VARCHAR(45), '.join(collist),
' VARCHAR(45))'])
Because we used join, you need to specify the last column type separately (the third item in the list) to correctly close the query.
NOTE: If the input data comes from user input then this would be susceptible to SQL injection since you are just formatting unknown strings in, to be executed. I am assuming the list of column names is internal to your program.

If statement in Flask using string variable from SQL database

I'm creating a program where I need to check if a certain cell in a table equals a string value and, if it does not, to not change that value. Here is some snippet of the code for clarification:
if (db.execute("SELECT :rowchosen FROM userboard WHERE column=:columnchosen", rowchosen = rowchosen, columnchosen = columnchosen)) == '-'):
#change value of cell
else:
#go to a new page that displays an error
Yet, whenever I run this code, I always get an error because the value (I believe) prints as a dictionary value, something like {"row" = 'row'} of that sort. Any help/advice as to why this happens?

Are you sure that userboard is the database and not the table?
i think, here is what you want to do
conn = sqlite3.connect(db_file)
cur = conn.cursor()
cur.execute("SELECT * FROM userboard WHERE one=?", (columnchosen,))
rows = cur.fetchall()
for row in rows:
print(row)
now, in the loop for row in rows: you need to perform your check. For all the rows returned, you need to check each row for - in the appropriate column
also check out http://www.sqlitetutorial.net/sqlite-python/sqlite-python-select/

Referencing row values in pyodbc when column name contains dashes (hyphens)

I am new to python and pyodbc
I try to print the first a row from a table from a progress openedge database. (Windows 7) Here is the code block that is not running:
cursor.execute("select my-nr, my-dt-my from mytable")
row = cursor.fetchone()
print(row.my-nr, row.my-dt-my)
This gives errors undefined name: 'nr'
undefined name 'dt'
undefined name 'my'
I guess it has something to do with the minus - symbols behind the dot . in print(row.my-nr, row.my-dt-my)
It was easy to print out the table names and column names from the database earlier but for some reason printing out rows is harder.
Any ideas how to get the rows printed?

pyodbc allows us to reference values in a pyodbc.Row object using the form row.column_name provided that the column names are legal Python identifiers. So, for example, we can do something like
row = crsr.fetchone()
print(row.city)
to print the value of the "city" column. Unfortunately, my-nr is not a legal Python identifier so if we try to print the value of the "my-nr" column using ...
row = crsr.fetchone()
print(row.my-nr) # error
... Python parses that as "row.my minus nr" where row.my would be interpreted as a column in the Row object and nr would be interpreted as a Python variable.
To work around the issue we can grab a list of the column names, merge those names with the row values into a dictionary, and then refer to the values in the dictionary:
crsr.execute(sql)
col_names = [x[0] for x in crsr.description]
row = crsr.fetchone()
row_as_dict = dict(zip(col_names, row))
print(row_as_dict['my-nr']) # no error

The most simple solution I can think of is this. First, columns containing hyphens need to be quoted in OpenEdge (see here). Second, you can alias the columns so they can be referenced as valid Python attributes. You'll need to do something like this:
cursor.execute('select "my-nr" as mynr, "my-dt-my" as mydtmy from mytable')
row = cursor.fetchone()
print(row.mynr, row.mydtmy)
Good luck!

I beleive that you need to change the variable names of the database, make sure they don't contain any '-' characters.
Variables can not contain characters reserved by python. For example you have to avoid hyphens(-), exclamation marks (!), colons (:) and so on.
According to this answer it seems like underscore (_) is the only character allowed in variable names.

sqlite - return all columns for max of one column without repeats

Im using Python to query a SQL database. I'm fairly new with databases. I've tried looking up this question, but I can't find a similar enough question to get the right answer.
I have a table with multiple columns/rows. I want to find the MAX of a single column, I want ALL columns returned (the entire ROW), and I want only one instance of the MAX. Right now I'm getting ten ROWS returned, because the MAX is repeated ten times. I only want one ROW returned.
The query strings I've tried so far:
sql = 'select max(f) from cbar'
# this returns one ROW, but only a single COLUMN (a single value)
sql = 'select * from cbar where f = (select max(f) from cbar)'
# this returns all COLUMNS, but it also returns multiple ROWS
I've tried a bunch more, but they returned nothing. They weren't right somehow. That's the problem, I'm too new to find the middle ground between my two working query statements.

In SQLite 3.7.11 or later, you can just retrieve all columns together with the maximum value:
SELECT *, max(f) FROM cbar;
But your Python might be too old. In the general case, you can sort the table by that column, and then just read the first row:
SELECT * FROM cbar ORDER BY f DESC LIMIT 1;

How do I select a column by its name? (Python & SQLite3)

Currently I have the following code:
c.execute("SELECT * FROM table")
for row in c.fetchall():
print row[0]
print row[1]
However, I changed the structure of my table and now I have to change the index values to represent this change. Is there a way to get use column names instead?

See Row Objects in the docs for the sqlite3 module. If you use the sqlite3.Row row_factory you'll get back an object that's slightly more powerful than the normal tuples. I imagine it has slightly higher overhead, hence not being the default behavior.

For this reason, it is recommended to always use explicit column names when doing a SELECT:
c.execute("SELECT color, fluffiness FROM table")
for row in c.fetchall():
print row[0] # <-- is always guaranteed to be the color value
print row[1]