We Keep Coding

How to update certain group of values in single column using SQL

I'm brand new in python and updating tables using sql. I would like to ask how to update certain group of values in single column using SQL. Please see example below:
id
123
999991234
235
789
200
999993456
I need to add the missing prefix '99999' to the records without '99999'. The id column has integer data type by default. I've tried the sql statement, but I have a conflict between data types that's I've tried with cast statement:
update tablename
set id = concat('99999', cast(id as string))
where id not like '99999%';

To be able to use the LIKE operator and CONCAT() function, the column data type should be a STRING or BYTE. In this case, you would need to cast the WHERE clause condition as well as the value of the SET statement.
Using your sample data:
Ran this update script:
UPDATE mydataset.my_table
SET id = CAST(CONCAT('99999', CAST(id AS STRING)) AS INTEGER)
WHERE CAST(id as STRING) NOT LIKE '99999%'
Result:
Rows were updated successfully and the table ended up with this data:

How do I pass variables in SQL3 python? [duplicate]

I create a table with primary key and autoincrement.
with open('RAND.xml', "rb") as f, sqlite3.connect("race.db") as connection:
c = connection.cursor()
c.execute(
"""CREATE TABLE IF NOT EXISTS race(RaceID INTEGER PRIMARY KEY AUTOINCREMENT,R_Number INT, R_KEY INT,\
R_NAME TEXT, R_AGE INT, R_DIST TEXT, R_CLASS, M_ID INT)""")
I want to then insert a tuple which of course has 1 less number than the total columns because the first is autoincrement.
sql_data = tuple(b)
c.executemany('insert into race values(?,?,?,?,?,?,?)', b)
How do I stop this error.
sqlite3.OperationalError: table race has 8 columns but 7 values were supplied

It's extremely bad practice to assume a specific ordering on the columns. Some DBA might come along and modify the table, breaking your SQL statements. Secondly, an autoincrement value will only be used if you don't specify a value for the field in your INSERT statement - if you give a value, that value will be stored in the new row.
If you amend the code to read
c.executemany('''insert into
race(R_number, R_KEY, R_NAME, R_AGE, R_DIST, R_CLASS, M_ID)
values(?,?,?,?,?,?,?)''',
sql_data)
you should find that everything works as expected.

From the SQLite documentation:
If the column-name list after table-name is omitted then the number of values inserted into each row must be the same as the number of columns in the table.
RaceID is a column in the table, so it is expected to be present when you're doing an INSERT without explicitly naming the columns. You can get the desired behavior (assign RaceID the next autoincrement value) by passing an SQLite NULL value in that column, which in Python is None:
sql_data = tuple((None,) + a for a in b)
c.executemany('insert into race values(?,?,?,?,?,?,?,?)', sql_data)
The above assumes b is a sequence of sequences of parameters for your executemany statement and attempts to prepend None to each sub-sequence. Modify as necessary for your code.

How can I get a MySQL database to insert a default value if there's an attempt to insert a null value with Python?

I've read answers that do something similar but not exactly what I'm looking for, which is: attempting to insert a row with a NULL value in a column will result instead in that column's DEFAULT value being inserted.
I'm trying to process a large number of inserts in the mySQL Python connector with a large number of column values that I don't want to deal with individually, and none of the typical alternatives work here. Here is a sketch of my code:
qry = "INSERT INTO table (col1, col2, ...) VALUES (%s, %s, ...)"
row_data_dict = defaultdict(lambda : None, {...})
params = []
for col in [col1, col2, ...]:
params.append(row_data_dict[col])
cursor.execute(qry, tuple(params))
My main problem is that setting None as the default in the dictionary results in either NULL being inserted or an error if I specify the row as NOT NULL. I have a large number of columns that might change in the future so I'd want to avoid setting different 'default' values for different entries if at all possible.
I can't do the typical way of inserting DEFAULT by skipping over columns on the insert because while those columns might have the DEFAULT value, I can't guarantee it and considering I'm doing a large number of inserts I don't want to change the query string each time I insert depending on if it's default or not.
The other way of inserting DEFAULT seems to be to have DEFAULT as one of the parameters (e.g. INSERT INTO table (col1,...) VALUES (DEFAULT,...)) but in my case setting the default in the dictionary to 'DEFAULT' results in error (mySQL complains about it being an incorrect integer value on trying to insert into an integer column, making it seem like it's interpreting the default as a string and not a keyword).
This seems like it would be a relatively common use case, so it kind of shocks me that I can't figure out a way to do this. I'd appreciate any way to do this or get around it that I haven't already listed here.
EDIT: All the of the relevant columns are already labeled with a DEFAULT value, it doesn't seem to actually replace NULL (or python's None) when it's inserted.
EDIT 2: The reason why I want to avoid NULL so badly is because NULL != NULL and I want to have unique rows, so that if there's one row (1, 2, 3, 'Unknown'), INSERT IGNORE'ing a row (1, 2, 3, 'Unknown') won't insert it. With NULL you end up with a bunch of copies of the same record because one of the values is unknown.

You can use the DEFAULT() function in the VALUES list to specify that default value for the column should be used. And you can put this in an IFNULL() call so it will be used when the supplied value is NULL.
qry = """INSERT INTO table (col1, col2, ...)
VALUES (IFNULL(%s, DEFAULT(col1)), IFNULL(%s, DEFAULT(col2)), ...)"""

Welcome to Stackoverflow. What you need to do is in your database add a default value for the column you want to have the default value. When you create your table just use DEFAULT and then the value after you create the column in the table, like this:
CREATE TABLE `yourTable` (`id` INT DEFAULT 0, .....)
if you have already created the table and you need to alter the existing column, you would do something like this:
ALTER TABLE `yourTable` MODIFY `id` INT DEFAULT 0
so in your insert statement coming from python, as long as you pass in either NULL or Nothing for the value of that column then when the row is inserted into your database, the default value will be populated for that column
Another thing to keep in mind is that you have to pass in the proper number of values when you have a default set up for a column. Say you have a table with 3 columns, we'll call them colA, colB and colC.
if you want to insert a row with colA_value for colA, nothing for colB so it will use it's default value and colC_value for colC then you need to still pass in 3 values that will be used for your insert. If you just passed in colA_value and colC_value, then colA will get colA_value and colB will get colC_value and colC will be null. you need to pass in values that will be interpreted by MySQL like this:
INSERT INTO `yourTable` (`colA`, `colB`, `colC`)
VALUES
('colA_value', null, 'colC_value')
even though you are not passing in anything for colB you need to pass a null value from your python program by either passing null or None to MySQL for the value for colB in order to get colB to be populated with it's default value
if you only pass in 2 values to MySQL to insert a row in your table, the insert statement under the hood will look like this:
INSERT INTO `yourTable` (`colA`, `colB`, `colC`)
VALUES
('colA_value', 'colC_value')
which would result in colA getting set to colA_value, colB getting set to colC_value and colC being left as null
if you are passing in the right number of values to be inserted into MySQL (that would mean you need to include null or None for the value to be inserted into the column with the default value) than that is another story. Please let me know if you are passing in the right number of values so I can help you troubleshoot further if needed.

Inserting NaN value into MySQL Database

I have some data that contains NULLs, floats and the occasional Nan. I'm trying to insert this data into a MySQL database using python and MySqldb.
Here's the insert statement:
for row in zip(currents, voltages):
row = [id] + list(row)
for item in row:
sql_insert = ('INSERT INTO result(id, current, voltage)'
'VALUES(%s, "%s")')
cursor.execute(sql_insert, row)
This is the table:
CREATE TABLE langmuir_result (result_id INT auto_increment,
id INT,
current FLOAT,
voltage FLOAT,
PRIMARY KEY (result_id));
When I try to insert NaN into the table I get this error:
_mysql_exceptions.DataError: (1265, "Data truncated for column 'current' at row 1")
I want to insert the NaN values into the database as a float or a number, not a string or NULL. I've tried having the type of the column be FLOAT and DECIMAL but get the same error. How can I do this without making it a string or NULL? Is that possible?

No, it's not possible to store a NaN value in a FLOAT type columns in Mysql. Values allowed are only NULL or a number. You may solve it using some value that you don't use for NaN (maybe negatives, a big/low value)

Try converting your NaN to None since MySQL understands None and in the UI you'll see NULL

You may use pandas package isna function:
import pandas as pd # use pandas package
if pd.isna(row[column]):
values_data.append(None)
else:
values_data.append(row[column])

which column of sql table is equal to a variable

i want to find the value of 'vazn' (one column of sql table) where 'id' column is equal to f1.
the table name is "billse"
"vazn" & "id1" are the columns of this table...
"f1" is a variable
f1 is a variable as following:
f1=int(enter3.get())
enter3 is an entry.
i entered the variable in enter3 that is equal to one of the existing 'id's in the sql table('bills')
this is my code:
self.cur.execute("SELECT vazn FROM billse WHERE id1='f1'")
vaznp = self.cur.fetchall()
print(vaznp)
i get 'null' when it prints vaznp
Why?

Use a prepared statement:
self.cur.execute("SELECT vazn FROM billse WHERE id1=?", f1)
vaznp = self.cur.fetchall()
print(vaznp)
Your current query is literally being interpreted as this:
SELECT vazn FROM billse WHERE id1='f1'
In other words, you are comparing the id1 column against the string 'f1', not against the value contained in that variable. Prepared statements also free you from the worry of dealing with properly escaping strings in your queries.