I'm trying to make a project where the user can also create a table. Initially I was getting tables as json from the user and adding them as a column of a table named application. but from some problems now I have to make the user also create a table directly.
If we come to the question exactly, let's assume that there is such a table.
name = "t_name"
rows = ["column1","column2","column3"]
how can i convert this to:
t_name = Table(
't_name', meta,
Column('column1', String),
Column('column2', String),
Column('column3', String),
)
I solved the problem in a similar way.
columns_names = ['id','date','name',"username","password"]
columns_types = [Integer,DateTime]
primary_key_flag = [True,False]
for i in columns_names:
primary_key_flag.append(False)
columns_types.append(VARCHAR(80))
Table(isim, meta,
*(Column(column_name, column_type,primary_key = primary_key_flag, column_nullable = True)
for column_name,
column_type,
primary_key_flag in zip(columns_names,
columns_types,
primary_key_flag)))
Related
Hi stack overflow community! This is my first question here, but I tried to find an answer beforehand. Right now I am working on loading data from json file like so (I actually have a json file named persons.json, not API) with the use of peewee to SQLite DB. As you can see, the json file has multiple nested dicts. My peewee model is as follows:
import json
import sqlite3
from peewee import *
db = SqliteDatabase('persons.sqlite3')
class Person(Model):
gender = CharField()
name = CharField()
location = CharField()
email = CharField()
login = CharField()
dob = CharField()
registered = CharField()
phone = CharField()
cell = CharField()
id_ = CharField()
picture = CharField()
nat = CharField()
count_dob = IntegerField()
And this is how I load all the data from json file to SQLite DB:
db.connect()
db.create_tables([Person])
with open('persons.json', encoding='utf8') as persons:
persons_data = json.load(persons)
for person in persons_data['results']:
p = Person(gender=person['gender'], name=person['name'], location=person['location'], email=person['email'],
login=person['login'], dob=person['dob'], registered=person['registered'], phone=person['phone'],
cell=person['cell'], id_=person['id'], picture=person['picture'], nat=person['nat'])
My question is, do you think the variables in my model are correctly defined (basically every single one of them as a CharField) ? The thing is, later whenever I query the DB and I need to access some of these nested dictionaries, they are actually a string, which I can convert with the use of ast.literal_eval back to dict, but I don't think it looks nice. I thought of a solution - for all the 'dictionary type' variables in my model ('location', 'dob' etc), instead of using CharField() I could probably use JSONField() - not sure how to do that though. Could you please advise on that one?
Relational databases do not support "nesting". It's foundational. Anything that is nested should probably be in a separate table or in its own column as a flat/scalar value.
https://en.wikipedia.org/wiki/Database_normalization
I've realized that in the newest version of SQLAlchemy (v1.0.4) I'm getting errors when using the table.c.keys() for selecting columns.
from sqlalchemy import MetaData
from sqlalchemy import (Column, Integer, Table, String, PrimaryKeyConstraint)
metadata = MetaData()
table = Table('test', metadata,
Column('id', Integer,nullable=False),
Column('name', String(20)),
PrimaryKeyConstraint('id')
)
stmt = select(table.c.keys()).select_from(table).where(table.c.id == 1)
In previous versions it used to work fine, but now this is throwing the following errors:
sqlalchemy/sql/elements.py:3851: SAWarning: Textual column expression 'id' should be explicitly declared with text('id'), or use column('id') for more specificity.
sqlalchemy/sql/elements.py:3851: SAWarning: Textual column expression 'name' should be explicitly declared with text('name'), or use column('name') for more specificity.
Is there a function for retrieving all these table columns rather than using a list comprehension like the following? [text(x) for x in table.c.keys()]
No, but you can always roll your own.
def all_columns(model_or_table, wrap=text):
table = getattr(model_or_table, '__table__', model_or_table)
return [wrap(col) for col in table.c.keys()]
then you would use it like
stmt = select(all_columns(table)).where(table.c.id == 1)
or
stmt = select(all_columns(Model)).where(Model.id == 1)
Note that in most cases you don't need select_from, i.e when you don't actually join to some other table.
I have this form in C# with a listbox where I selected 4 items. Now I want to make single stored procedure using which I can find data from single table for all this selected item with single parameter.
As I am a beginner when it comes to SQL Server, I completely don't know this type of procedure
Thanks, but this is not my question's answer
I want a Single Stored Procedure for all Items which are selected in ListBox
Create Procedure procedureName
(
#ItemName varchar(50),
)
AS
BEGIN
(
Select * from item_master where item_name = #ItemName
)
END
by this Query i can find data for one ItemName, but i want for all selected Items in Listbox, even I don't know the C# code also,
so plz help me....
This is a very simple example that does what you want. You would not want to use hard-coded connection strings, especially in-line, and you would want error-handling, but I am going for as much clarity as possible. You would also probably want to make the column length greater than 50 characters, but I made it match your column definition.
Also, I would recommend a generic approach, passing keys (column names) and values, so as to be able to use it for any sort of criteria, but you asked that I keep it to exactly what you require, so I trimmed it down to the essential.
This example returns all the Employees with FirstName matching any in the list passed to the stored procedure (as a user-defined table type).
First, create a user-defined table type (to hold the values you want to pass to the stored procedure) in your SQL Server database as follows:
CREATE TYPE [dbo].[FilterValues] AS TABLE(
[Value] [varchar](50) NOT NULL,
PRIMARY KEY CLUSTERED
(
[Value] ASC
)
)
The stored procedure to return the Employees looks as follows (note that it has the user-defined table type as the type of the single parameter passed in):
CREATE PROCEDURE [dbo].[GetEmployees] (
#FirstNameFilterValues dbo.FilterValues READONLY
)
AS
BEGIN
SELECT * FROM Employees
INNER JOIN #FirstNameFilterValues fv ON fv.Value = Employees.FirstName;
END
That's the SQL Server side done. To call it from C#, you can create a DataTable with a single column matching the column name and populate it with the values you want. In this simple example, I populate it with two names, but it could be as many as you want.
var filterValuesDataTable = new DataTable();
filterValuesDataTable.Columns.Add(new DataColumn("Value", typeof(string)) { AllowDBNull = false });
filterValuesDataTable.Rows.Add("Frodo");
filterValuesDataTable.Rows.Add("Sam");
using (var connection = new SqlConnection("server=.;Initial Catalog=Test;Integrated Security=True;"))
{
connection.Open();
using (var command = connection.CreateCommand())
{
command.CommandText = "GetEmployees";
command.CommandType = CommandType.StoredProcedure;
command.Parameters.AddWithValue("#FirstNameFilterValues", filterValuesDataTable);
using (var reader = command.ExecuteReader())
{
while (reader.Read())
{
Console.WriteLine("{0} {1}", reader["FirstName"], reader["LastName"]);
}
reader.Close();
}
}
connection.Close();
}
Very similar to this question MySQL Dynamic Query Statement in Python
However what I am looking to do instead of two lists is to use a dictionary
Let's say i have this dictionary
instance_insert = {
# sql column variable value
'instance_id' : 'instnace.id',
'customer_id' : 'customer.id',
'os' : 'instance.platform',
}
And I want to populate a mysql database with an insert statement using sql column as the sql column name and the variable name as the variable that will hold the value that is to be inserted into the mysql table.
Kind of lost because I don't understand exactly what this statement does, but was pulled from the question that I posted where he was using two lists to do what he wanted.
sql = "INSERT INTO instance_info_test VALUES (%s);" % ', '.join('?' for _ in instance_insert)
cur.execute (sql, instance_insert)
Also I would like it to be dynamic in the sense that I can add/remove columns to the dictionary
Before you post, you might want to try searching for something more specific to your question. For instance, when I Googled "python mysqldb insert dictionary", I found a good answer on the first page, at http://mail.python.org/pipermail/tutor/2010-December/080701.html. Relevant part:
Here's what I came up with when I tried to make a generalized version
of the above:
def add_row(cursor, tablename, rowdict):
# XXX tablename not sanitized
# XXX test for allowed keys is case-sensitive
# filter out keys that are not column names
cursor.execute("describe %s" % tablename)
allowed_keys = set(row[0] for row in cursor.fetchall())
keys = allowed_keys.intersection(rowdict)
if len(rowdict) > len(keys):
unknown_keys = set(rowdict) - allowed_keys
print >> sys.stderr, "skipping keys:", ", ".join(unknown_keys)
columns = ", ".join(keys)
values_template = ", ".join(["%s"] * len(keys))
sql = "insert into %s (%s) values (%s)" % (
tablename, columns, values_template)
values = tuple(rowdict[key] for key in keys)
cursor.execute(sql, values)
filename = ...
tablename = ...
db = MySQLdb.connect(...)
cursor = db.cursor()
with open(filename) as instream:
row = json.load(instream)
add_row(cursor, tablename, row)
Peter
If you know your inputs will always be valid (table name is valid, columns are present in the table), and you're not importing from a JSON file as the example is, you can simplify this function. But it'll accomplish what you want to accomplish. While it may initially seem like DictCursor would be helpful, it looks like DictCursor is useful for returning a dictionary of values, but it can't execute from a dict.
I am hoping you can help. I am developing a tiered website using Linq to Sql. I created a new class(or object) in DBML designer called memberState. This object is not an actual table in the database. I have this method in my middle layer:
public override IEnumerable(memberState) GetMembersByState(string #state)
{
using (BulletinWizardDataContext context = DataContext)
{
IEnumerable(memberState) mems = (from m in context.Members
join ma in context.MemberAddresses
on m.UserId equals ma.UserId
join s in context.States
on ma.StateId equals s.StateId
where s.StateName == #state
select new memberState
{
userId = m.UserID,
firstName = m.FirstName,
middleInitial = m.MiddleInitial,
lastName = m.LastName,
createDate = m.CreateDate,
modifyDate = m.ModifyDate
}).ToArray(memberState)();
return mems;
}
}
The tables in my joins (Members, States, and MemberAddresses are actual tables in my Database). I created the object memberStates so I could use it in the query above (notice the Select New memberState. When the data is updated on the web page how do I persist the changes back to the Member Table? My Member Table consists of the following columns: UserId, FirstName, MiddleInitial, LastName, CreateDate, ModifyDate. I am not sure how save the changes back to the database.
Thanks,
If I remember correctly, you can create a view from the different tables (Members, States, and MemberAddresses) and add that to the data context. Then any modifications to data in the view object can be saved, and linq to sql will handle the commit correctly as long as all the relationships are clearly setup/defined in both the database and in the data context.
If you have a Member table, the dbml will most likely contain a Member class. To update a member in the database, you will have to create a new Member object, and the Attach it to the BulletinWizardDataContext.Members collection. Something similar to the following code should the trick (I have not tested the code):
using (BulletinWizardDataContext context = DataContext)
{
Member m = new Member() { UserId = userId };
context.Members.Attach(m);
m.FirstName = firstName;
// Set other properties
context.SubmitChanges();
}
Attach must be called before setting the properties. Also, Linq2Sql has some issues with Attach in the case where the properties of your object are set to default values (i.e. 0 for numeric values, false for booleans, null for string etc.). In this case Attach will not generate the correct SQL.
var m = myContext.Members.Single(m=> m.UserID == myMemState.userID);
m.FirstName = myMemState.firstName;
m.MiddleInitial = myMemState.middleInitial;
...
That would be the quick way. It does an additional roundtrip to the db, but will work well. If that's an issue for you, then do Attach like Jakob suggested. For that you have to have to do some extra steps, like reviewing the configuration for optimistic updates and make sure you have the original fields when doing the attach.