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Rails migrations: Undo default setting for a column
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Rails 5+
def change
change_column_default( :table_name, :column_name, from: nil, to: false )
end
Rails 3 and Rails 4
def up
change_column_default( :table_name, :column_name, nil )
end
def down
change_column_default( :table_name, :column_name, false )
end
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Difference between one-to-many and many-to-one relationship
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From this page about Database Terminology
Most relations between tables are one-to-many.
Example:
One area can be the habitat of many readers.
One reader can have many subscriptions.
One newspaper can have many subscriptions.
A Many to One relation is the same as o...
Select top 10 records for each category
.... Can anyone help with how to do it? Section is one of the columns in the table.
14 Answers
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How to find foreign key dependencies in SQL Server?
... all Foreign Key Relationships within the current database.
SELECT
FK_Table = FK.TABLE_NAME,
FK_Column = CU.COLUMN_NAME,
PK_Table = PK.TABLE_NAME,
PK_Column = PT.COLUMN_NAME,
Constraint_Name = C.CONSTRAINT_NAME
FROM
INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C
INNER JOIN INF...
UITableView - scroll to the top
In my table view I have to scroll to the top. But I cannot guarantee that the first object is going to be section 0, row 0. May be that my table view will start from section number 5.
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How do I delete a fixed number of rows with sorting in PostgreSQL?
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You could try using the ctid:
DELETE FROM logtable
WHERE ctid IN (
SELECT ctid
FROM logtable
ORDER BY timestamp
LIMIT 10
)
The ctid is:
The physical location of the row version within its table. Note that although the ctid can be used to locate the...
What's the difference between belongs_to and has_one?
...oreign key is. We can say that a User "has" a Profile because the profiles table has a user_id column. If there was a column called profile_id on the users table, however, we would say that a Profile has a User, and the belongs_to/has_one locations would be swapped.
here is a more detailed explanat...
Browsers' default CSS for HTML elements
...}
li { display: list-item }
head { display: none }
table { display: table }
tr { display: table-row }
thead { display: table-header-group }
tbody { display: table-row-group }
tfoot { display: table-footer-group }
col ...
How can I create a unique constraint on my column (SQL Server 2008 R2)?
...@WhiteIsland - You should see it in SSMS object Explorer if you expand the table and look under "Keys"
– Martin Smith
Mar 3 '11 at 18:43
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Add a default value to a column through a migration
...an a change block. You can leave the down block empty. It won't revert the table to the original condition but the migration can be rolled back.
– IAmNaN
May 16 '14 at 1:16
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