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Entity Framework rollback and remove bad migration
...command:
PM> get-help entityframework
Refreshing dastabase in VS2015 SQL Server Object Explorer, all of my data was preserved and the migration that I wanted to revert was gone :)
Initially I tried Remove-Migration by itself and found the error command confusing:
System.InvalidOperationEx...
Good ways to sort a queryset? - Django
...
I just wanted to illustrate that the built-in solutions (SQL-only) are not always the best ones. At first I thought that because Django's QuerySet.objects.order_by method accepts multiple arguments, you could easily chain them:
ordered_authors = Author.objects.order_by('-score', ...
Windows batch: formatted date into variable
... Agreed. Some of the answers here look almost like "Install MS SQL Server, connect with a SQL Client, and execute the command SELECT CONVERT(VARCHAR(16), GETDATE(), 112)".
– isapir
Oct 13 '17 at 20:38
...
Django select only rows with duplicate field values
...sting ordering. If you have a model-set ordering, this becomes part of the SQL GROUP BY clause, and that breaks things. Found that out when playing with Subquery (in which you do very similar grouping via .values())
– Oli
Jun 6 '17 at 9:01
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Query for array elements inside JSON type
I'm trying to test out the json type in PostgreSQL 9.3.
I have a json column called data in a table called reports . The JSON looks something like this:
...
Postgres dump of only parts of tables for a dev snapshot
... TO '/tmp/myfile.tsv'
COPY mytable FROM 'myfile.tsv'
https://www.postgresql.org/docs/current/static/sql-copy.html
You should consider maintaining a set of development data rather than just pulling a subset of your production. In the case that you're writing unit tests, you could use the same da...
SqlException from Entity Framework - New transaction is not allowed because there are other threads
...e exception you were seeing.
EDIT I revisited this question after running SQL Profiler and updated a few things to improve performance. For anyone who is interested, here is some sample SQL that shows what is created by the DB.
The first loop doesn't need to skip anything, so is simpler.
SELECT ...
How to serialize SqlAlchemy result to JSON?
...
A flat implementation
You could use something like this:
from sqlalchemy.ext.declarative import DeclarativeMeta
class AlchemyEncoder(json.JSONEncoder):
def default(self, obj):
if isinstance(obj.__class__, DeclarativeMeta):
# an SQLAlchemy class
fiel...
When to use Common Table Expression (CTE)
...bout Common table expression that is a new feature which was introduced in SQL server 2005 and available in later versions as well.
Common table Expression :- Common table expression can be defined as a temporary result set or in other words its a substitute of views in SQL Server. Common table ex...
Can a foreign key be NULL and/or duplicate?
...lls leave lots of room for errors in the query by folks who don't know how SQL (mis)handles 3VL . If a salesperson is truly not necessary for a certain r-table, just you don't include that record. A separate table can be "ProposalAssignedTo" or some such, with appropriate constraints. A query writer...