大约有 37,000 项符合查询结果（耗时：0.0183秒） [XML]
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
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If you use UITableViewController instead of UIViewController, it will automatically do so.
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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...
Can hash tables really be O(1)?
It seems to be common knowledge that hash tables can achieve O(1), but that has never made sense to me. Can someone please explain it? Here are two situations that come to mind:
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Does MySQL index foreign key columns automatically?
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Yes, but only on innodb. Innodb is currently the only shipped table format that has foreign keys implemented.
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Selecting data from two different servers in SQL Server
...edserver.
You only have to set up one. Once you have that, you can call a table on the other server like so:
select
*
from
LocalTable,
[OtherServerName].[OtherDB].[dbo].[OtherTable]
Note that the owner isn't always dbo, so make sure to replace it with whatever schema you use.
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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 ...
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...
Get table name by constraint name [duplicate]
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SELECT owner, table_name
FROM dba_constraints
WHERE constraint_name = <<your constraint name>>
will give you the name of the table. If you don't have access to the DBA_CONSTRAINTS view, ALL_CONSTRAINTS or USER_CONSTRAINTS...
Cannot use a CONTAINS or FREETEXT predicate on table or indexed view because it is not full-text ind
...ex, make sure:
- you don't already have full-text search index on the table as only one full-text search index allowed on a table
- a unique index exists on the table. The index must be based on single-key column, that does not allow NULL.
- full-text catalog exists. You have to speci...