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What's wrong with nullable columns in composite primary keys?
...n optionally be related to B, the clean solution is to create a resolution table (let's say AB). That table would link A with B: If there is a relationship then it would contain a record, if there isn't then it would not.
sh...
What are the differences between a clustered and a non-clustered index?
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Clustered Index
Only one per table
Faster to read than non clustered as data is physically stored in index order
Non Clustered Index
Can be used many times per table
Quicker for insert and update operations than a clustered index
Both types of inde...
Add new column with foreign key constraint in one command
...to add the column and the foreign key constraint using two separate ALTER TABLE commands:
12 Answers
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How to create id with AUTO_INCREMENT on Oracle?
...acle 11g. However, you can model it easily with a sequence and a trigger:
Table definition:
CREATE TABLE departments (
ID NUMBER(10) NOT NULL,
DESCRIPTION VARCHAR2(50) NOT NULL);
ALTER TABLE departments ADD (
CONSTRAINT dept_pk PRIMARY KEY (ID));
CREATE SEQUENCE dept_seq STA...
Getting the name of a child class in the parent class (static context)
...lt;?php
class Base
{
public static function find($id)
{
$table = static::$_table;
$class = static::getClass();
// $data = find_row_data_somehow($table, $id);
$data = array('table' => $table, 'id' => $id);
return new $class($data);
}
pu...
When to use a “has_many :through” relation in Rails?
...p
# has attributes for date_joined and role
end
This introduces a new table, and eliminates the group_id column from the user's table.
The problem with this code is that you'd have to update every where else you use the user class and change it:
user.groups.first.name
# becomes
user.group_m...
Making a UITableView scroll when text field is selected
...
If you use UITableViewController instead of UIViewController, it will automatically do so.
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How to execute a raw update sql with dynamic binding in rails
... MySQL:
st = ActiveRecord::Base.connection.raw_connection.prepare("update table set f1=? where f2=? and f3=?")
st.execute(f1, f2, f3)
st.close
I'm not sure if there are other ramifications to doing this (connections left open, etc). I would trace the Rails code for a normal update to see what it'...
PostgreSQL query to return results as a comma separated list
Let say you have a SELECT id from table query (the real case is a complex query) that does return you several results.
5 ...
How to select the last record of a table in SQL?
This is a sample code to select all records from a table. Can someone show me how to select the last record of that table?
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