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Effect of NOLOCK hint in SELECT statements
...2) Yes, a select with NOLOCK will allow other queries against the effected table to complete faster than a normal select.
Why would this be?
NOLOCK typically (depending on your DB engine) means give me your data, and I don't care what state it is in, and don't bother holding it still while you re...
Does the join order matter in SQL?
... neither predicate can be satisfied by a row in which all columns from one table are NULL, than to say that it's associative as long as the predicates don't involve IS NULL or 'a function that is related to nulls'. One can easily imagine a predicate that satisfies the former description but not the ...
select count(*) from table of mysql in php
...
here is the code for showing no of rows in the table with PHP
$sql="select count(*) as total from student_table";
$result=mysqli_query($con,$sql);
$data=mysqli_fetch_assoc($result);
echo $data['total'];
...
How to make an empty div take space
...p;nbsp; to the empty items.
I don't understand why you're not using a <table> here, though? They will do this kind of stuff automatically.
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Throw an error in a MySQL trigger
If I have a trigger before the update on a table, how can I throw an error that prevents the update on that table?
7 An...
Which is fastest? SELECT SQL_CALC_FOUND_ROWS FROM `table`, or SELECT COUNT(*)
...ent and SQLC_CALC_FOUND_ROWS was much faster than two queries. Now my main table is only 65k and two joins of a few hundreds, but the main query takes 0.18 seconds with or without SQLC_CALC_FOUND_ROWS but when I ran a second query with COUNT(id) it took 0.25 alone.
– transilvla...
Getting the name of a child class in the parent class (static context)
...lt;?php
class Base
{
public static function find($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...
How do I cast a string to integer and have 0 in case of error in the cast with PostgreSQL?
In PostgreSQL I have a table with a varchar column. The data is supposed to be integers and I need it in integer type in a query. Some values are empty strings.
The following:
...
SQL WHERE condition is not equal to?
...
You can do like this
DELETE FROM table WHERE id NOT IN ( 2 )
OR
DELETE FROM table WHERE id <> 2
As @Frank Schmitt noted, you might want to be careful about the NULL values too. If you want to delete everything which is not 2(including the NULLs...
Restoring MySQL database from physical files
...
A MySQL MyISAM table is the combination of three files:
The FRM file is the table definition.
The MYD file is where the actual data is stored.
The MYI file is where the indexes created on the table are stored.
You should be able to rest...