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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...
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 ...
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...
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...
Remove Trailing Spaces and Update in Columns in SQL Server
I have trailing spaces in a column in a SQL Server table called Company Name .
13 Answers
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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...
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:
...
Restoring MySQL database from physical files
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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...
How do I specify unique constraint for multiple columns in MySQL?
I have a table:
14 Answers
14
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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'...