Павел

CREATE TRIGGER `name` AFTER INSERT ON `table`
FOR EACH ROW
BEGIN
INSERT IGNORE INTO `table2`(`val`) VALUES (NEW.`myval`);
END

SELECT a.category_id AS id, COUNT(b.product_id) AS p_count
FROM a
LEFT JOIN b ON a.product_id=b.product_id and b.manufacturer_id = 'Мелкософт'
GROUP BY id

UPDATE products p 
    JOIN update_info ui ON t.id =  ui.id
SET p.price = ui.price

$all_sales_select = mysql_query('
    SELECT sc.*, wpu.money, scm.value
    FROM sales_catalog sc 
    LEFT JOIN wp_users wpu 
      ON sc.sale_provider_id = wpu.ID 
    LEFT JOIN (select sale_id, max(value) as value
               from sales_catalog_meta 
               WHERE type = "image"
               group by sale_id) scm
      ON sc.sale_id = scm.sale_id
    WHERE sc.sale_provider_id="'.$user_id.'" 
    ORDER BY sc.insert_date, sc.sale_id') or die(mysql_error());

Warning

Never, never, NEVER use Python string concatenation (+) or string parameters interpolation (%) to pass variables to a SQL query string. Not even at gunpoint.