not-exists

I have a problem with django migrations. I get this error: django.db.migrations.exceptions.NodeNotFoundError: Migration user.0050_merge_20170523_1254 dependencies reference nonexistent parent node ('user', '0049_auto_20170519_1934') I fix the errors, deleting some lines but after fix all this errors, I get other: ValueError: Could not find common ancestor of {'0050_merge_20170523_1254', '0007_auto_20170524_1540'} I cant solve that. I can drop database and do makemigrations again... but in production environment I want know how fix correctly, without drop database haha. Thanks! Next time when

I am having problem with selecting values from table a (id, room_name) where there are no corresponding events in table b (room_id, room_start, room_finish) my query looks following SELECT id, room_name FROM rooms WHERE NOT EXISTS (SELECT * FROM room_events WHERE room_start BETWEEN '1294727400' AND '1294729200' OR room_finish BETWEEN '1294727400' AND '1294729200') table a contains multiple rooms, table b contains room events I am getting no results in case there is any event for any of the rooms within the timestamps. I am expecting all rooms having NO events. Here is the prototype for what

I'd like to combine an insert query with a "where not exists" so as not to violate PK constraints. However, syntax such as the following gives me an Incorrect syntax near the keyword 'WHERE' error - INSERT INTO myTable(columns...) VALUES(values...) WHERE NOT EXISTS (SELECT * FROM myTable WHERE pk_part1 = value1, AND pk_part2 = value2) How can I accomplish this? (In general, can you combine an insert with a where clause?) INSERT INTO myTable(columns...) Select values... WHERE NOT EXISTS (SELECT * FROM myTable WHERE pk_part1 = value1, AND pk_part2 = value2) Edit: After reading martins link, If

I want to write a query for MS SQL Server that adds a column into a table. But I don't want any error display, when I run/execute the following query. I am using this sort of query to add a table ... IF EXISTS ( SELECT * FROM sys.objects WHERE OBJECT_ID = OBJECT_ID(N'[dbo].[Person]') AND TYPE IN (N'U') ) But I don't know how to write this query for a column. Lieven Keersmaekers You can use a similar construct by using the sys.columns table io sys.objects . IF NOT EXISTS ( SELECT * FROM sys.columns WHERE object_id = OBJECT_ID(N'[dbo].[Person]') AND name = 'ColumnName' ) SPL IF COL_LENGTH('table

I have a MySQL query that joins two tables Voters Households they join on voters.household_id and household.id Now what i need to do is to modify it where the voter table is joined to a third table called elimination, along voter.id and elimination.voter_id, how ever the catch is that i want to exclude any records in the voter table that have a corresponding record in the elimination table. how do i craft a query to do this? this is my current query SELECT `voter`.`ID`, `voter`.`Last_Name`, `voter`.`First_Name`, `voter`.`Middle_Name`, `voter`.`Age`, `voter`.`Sex`, `voter`.`Party`, `voter`.

I have 2 tables (A and B) with the same primary keys. I want to select all row that are in A and not in B. The following works: select * from A where not exists (select * from B where A.pk=B.pk); however it seems quite bad (~2 sec on only 100k rows in A and 3-10k less in B) Is there a better way to run this? Perhaps as a left join? select * from A left join B on A.x=B.y where B.y is null; On my data this seems to run slightly faster (~10%) but what about in general? I use queries in the format of your second example. A join is usually more scalable than a correlated subquery. Nick Berardi I