I have a table using SQL Lite with Python. The size of the table always has 3 columns and could have many rows. Each of the cells are strings. Here is example table:
serial_num date_measured status
1234A 1-1-2015 passed
4321B 6-21-2015 failed
1423C 12-25-2015 passed
......
My program prompts me for a serial number. This is saved as a variable called serialNum. How can I delete (or overwrite) an entire row if serialNum equals any of the strings in the serial_num column in my table?
I've seen many examples on how to delete (or overwrite) a row in a table if I know all the values in each cell of that row, but my trouble is that the only cell that could ever be the same in each row would be the serial number. I need to so a search through the serial_number column and if any string in that column equals the current value of my serialNum variable, I need to delete (or overwrite) that row.
import sqlite3
conn = sqlite3.connect('example.db')
c = conn.cursor()
c.execute('''CREATE TABLE test (serial_num text, date_measured text, status text)''')
c.execute("INSERT INTO test VALUES ('1234A', '1-1-2015', 'passed')")
c.execute("INSERT INTO test VALUES ('4321B', '6-21-2015', 'failed')")
c.execute("INSERT INTO test VALUES ('1423C', '12-25-2015', 'passed')")
conn.commit()
Does anyone know a simple way to do this? I've seen others say that an ID must be used or a temporary table, but I would hope there might be an easier way to accomplish my task. Any advice would be great.
SQL suports this: simply use delete
"delete from test where serial_num=<some input>;"
or in this case
c.execute("delete from test where serial_num=%s;", serialNum);
There's no need to search through the list when using SQL. SQL is declarative: you tell it what to do using your query, not how to do it. Don't loop though all your rows to check which to delete: tell it what to delete and the database engine will find the best/fastest way to satisfy that goal.
Hope I well interpreted your question
for row in c.execute('SELECT * FROM test WHERE serial_num = ?', serialNum'):
# do whatever you want on row
print row
I was able to figure out a working solution:
sql = "DELETE FROM test WHERE serial_num = ?"
c.execute(sql, (serialNum,))
The comma after serialNum for some reason has to be there. Thank you #Michiel Arienfor the head start
Related
I have two problems that are fairly similar. I am using Python to deal with SQL databases.
First, I want to only fetch the new data from a SQL database (that continously gets updated with new entries). If I have already selected that entire row I don't want it again, just get the new ones. The code I have right now is:
sql = ''' SELECT * FROM table WHERE time BETWEEN ? AND ? ''' #Select all columns of the database between the two timestamps
cur.execute(sql,[start_time,end_time])
Then I want to insert other data to another database but I don't want to add rows that are already there. My code at the moment is:
query = 'INSERT INTO table_2 (col_1, col_2, col_3, col_4, col_5, col_6) VALUES(%s, %s, %s, %s, %s, %s)'
my_data = []
for row in data_df:
my_data.append(tuple(row))
cur.executemany(query, my_data)
If have tried to use the WHERE NOT EXISTS feature but I am unsure of the syntaxis and I keep getting errors.
I'll try to help you
What I'm suggesting is to add a column integer in your Table that you can name as STATUS, and initialize it at value 0..
Then you will add a "WHERE" condition like : "WHERE STATUS = 0"
Then you'll UPDATE the selected row at STATUS = 1 (you should do it inside the transition)
If you can't handle the table no problem => you can make a temporary table that contains all the data you're needing and the column with the status
I mean you'll dump all your data in a temporary structure with one more column..
I am looking for a way to get a row from a database and every value in it. For example, by searching by Name or ItemNumber and the code will retrieve the value for Price or any other column value in the row. I have tried using this code and it returns every row and values for those rows instead of just 1 as I am looking for.
import sqlite3
cursor = sqliteConnection.cursor()
sqlite_select_query = """SELECT 374932 from ItemLookup"""
cursor.execute(sqlite_select_query)
rows = cursor.fetchall()
for row in rows:
print(row)
I have also used cursor.fetchone() and this returns 374932 provided in the SELECT 374932 from ItemLookup code multiple times. Using fetchmany() with any row[0] or row[1] values displays a tuple out of range error message. I have searched the internet and cannot find an explanation for this. Any help would be appreciated!
SQL queries generally follow the syntax of
SELECT field FROM table WHERE condition
for example, this is a query for Joe's information: SELECT * FROM ItemLookup WHERE Name = 'Joe'
You can use this to query the information you want based on specific conditions.
I am trying to upload data from a csv file (its on my local desktop) to my remote SQL database. This is my query
dsn = "dsnname";pwd="password"
import pyodbc
csv_data =open(r'C:\Users\folder\Desktop\filename.csv')
def func(dsn):
cnnctn=pyodbc.connect(dsn)
cnnctn.autocommit =True
cur=cnnctn.cursor()
for rows in csv_data:
cur.execute("insert into database.tablename (colname) value(?)", rows)
cur.commit()
cnnctn.commit()
cur.close()
cnnctn.close()
return()
c=func(dsn)
The problem is that all of my data gets uploaded in one col- that I specified. If I don't specify a col name it won't run. I have 9 cols in my database table and I want to upload this data into separate cols.
When you insert with SQL, you need to make sure you are telling which columns you want to be inserting on. For example, when you execute:
INSERT INTO table (column_name) VALUES (val);
You are letting SQL know that you want to map column_name to val for that specific row. So, you need to make sure that the number of columns in the first parentheses matches the number of values in the second set of parentheses.
I used python version 3.4.3 with the sqlite3 package.
I made mistake while transferring a load of .txt files into sqlite tables. Some of the .txt files had more than one header line. So somewhere in the resulting sql table there is a row containing column names of that table.
For example if I set up a table like this:
import sqlite3
con = sqlite3.connect(path to a db)
con.execute('CREATE TABLE A_table (Id PRIMARY KEY,name TEXT,value INTEGER)')
rows = [('Id','name','value'),(1,'Ted',111),(2,'Thelma',22)]
con.executemany('INSERT INTO A_table (Id,name,value) Values(?,?,?)',rows)
If I try to remove the row like this:
con.execute('DELETE FROM A_table WHERE name = "name"')
It deletes all rows in the table.
In my real database the row that needs to go is not always the first row it could appear at any point. Short of rebuilding the tables what should I do?
I am sure that this has be asked already but I don't have a clue what to call this problem so I have had 0 luck finding help.
Edit: I used python. I am not python.
Use a parametrized query:
con.execute("DELETE FROM A_table WHERE name=?", ('name'))
In SQL, strings use single quotes.
Double quotes are used to escape column names, so name = "name" is the same as name = name.
To avoid string formatting problems, it might be a better idea to use parameters:
con.execute("DELETE FROM A_table WHERE name = 'name';")
con.execute("DELETE FROM A_table WHERE name = ?;", ["name"]) # a Python string
i just started out with programmming and wrote a few lines of code in pyscripter using sqlite3.
The table "gather" is created beforehand. i then select certain rows from "gather" to put them into another table. i try to sort this table by a specific column 'date'. But it doesn't seem to work. it doesn't give me an error message or something like that. It's just not sorted. If i try the same command (SELECT * FROM matches ORDER BY date) in sqlitemanager, it works fine on the exact same table! what is the problem here? i googled quite some time, but i don't find a solution. it's proobably something stupid i'm missing..
as i said i'm a total newbie. i guess you all break out in tears looking at the code. so if you have any tips how i can shorten the code or make it faster or whatever, you're very welcome :) (but everything works fine except the above mentioned part.)
import sqlite3
connection = sqlite3.connect("gather.sqlite")
cursor1 = connection.cursor()
cursor1.execute('Drop table IF EXISTS matches')
cursor1.execute('CREATE TABLE matches(date TEXT, team1 TEXT, team2 TEXT)')
cursor1.execute('INSERT INTO matches (date, team1, team2) SELECT * FROM gather WHERE team1=? or team2=?, (a,a,))
cursor1.execute("SELECT * FROM matches ORDER BY date")
connection.commit()
OK, I think I understand your problem. First of all: I'm not sure if that commit call is necessary at all. However, if it is, you'll definitely want that to be before your select statement. 'connection.commit()' is essentially saying, commit the changes I just made to the database.
Your second issue is that you are executing the select query but never actually doing anything with the results of the query.
try this:
import sqlite3
connection = sqlite3.connect("gather.sqlite")
cursor1 = connection.cursor()
cursor1.execute('Drop table IF EXISTS matches')
cursor1.execute('CREATE TABLE matches(date TEXT, team1 TEXT, team2 TEXT)')
cursor1.execute('INSERT INTO matches (date, team1, team2) SELECT * FROM gather WHERE team1=? or team2=?, (a,a,))
connection.commit()
# directly iterate over the results of the query:
for row in cursor1.execute("SELECT * FROM matches ORDER BY date"):
print row
you are executing the query, but never actually retrieving the results. There are two ways to do this with sqlite3: One way is the way I showed you above, where you can just use the execute statement directly as an iteratable object.
The other way is as follows:
import sqlite3
connection = sqlite3.connect("gather.sqlite")
cursor1 = connection.cursor()
cursor1.execute('Drop table IF EXISTS matches')
cursor1.execute('CREATE TABLE matches(date TEXT, team1 TEXT, team2 TEXT)')
cursor1.execute('INSERT INTO matches (date, team1, team2) SELECT * FROM gather WHERE team1=? or team2=?, (a,a,))
connection.commit()
cursor1.execute("SELECT * FROM matches ORDER BY date")
# fetch all means fetch all rows from the last query. here you put the rows
# into their own result object instead of directly iterating over them.
db_result = cursor1.fetchall()
for row in db_result:
print row
Try moving the commit before the SELECT * (I'm not sure 100% that this is an issue) You then just need to fetch the results of the query :-) Add a line like res = cursor1.fetchall() after you've executed the SELECT. If you want to display them like in sqlitemanager, add
for hit in res:
print '|'.join(hit)
at the bottom.
Edit: To address your issue of storing the sort order to the table:
I think what you're looking for is something like a clustered index. (Which doesn't actually sort the values in th table, but comes close; see here).
SQLIte doesn't have such such indexes, but you can simulate them by actually ordering the table. You can only do this once, as you're inserting the data. You would need an SQL command like the following:
INSERT INTO matches (date, team1, team2)
SELECT * FROM gather
WHERE team1=? or team2=?
ORDER BY date;
instead of the one you currently use.
See point 4 here, which is where I got the idea.