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Add timestamps to an existing table
I need to add timestamps ( created_at & updated_at ) to an existing table. I tried the following code but it didn't work.
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How To Change DataType of a DataColumn in a DataTable?
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You cannot change the DataType after the Datatable is filled with data. However, you can clone the Data table, change the column type and load data from previous data table to the cloned table as shown below.
DataTable dtCloned = dt.Clone();
dtCloned.Columns[0].DataTyp...
How does database indexing work? [closed]
... N/2 block accesses (on average), where N is the number of blocks that the table spans. If that field is a non-key field (i.e. doesn’t contain unique entries) then the entire tablespace must be searched at N block accesses.
Whereas with a sorted field, a Binary Search may be used, which has log2 ...
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 ...
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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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...
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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Difference between Select Unique and Select Distinct
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Unique is a keyword used in the Create Table() directive to denote that a field will contain unique data, usually used for natural keys, foreign keys etc.
For example:
Create Table Employee(
Emp_PKey Int Identity(1, 1) Constraint PK_Employee_Emp_PKey Prim...
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...