Столбец

в таблице SQL. Я предоставлю вам несколько подходов и примеры кода для решения этой задачи с использованием различных систем баз данных.

Обратите внимание, что в примерах кода предполагается наличие таблицы со столбцом с именем updated_atв базе данных.

1. MySQL:

   -- Method 1: Use a TIMESTAMP column with the DEFAULT CURRENT_TIMESTAMP attribute
   ALTER TABLE your_table
   MODIFY COLUMN updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;
   -- Method 2: Use a TRIGGER to update the column on every update
   DELIMITER //
   CREATE TRIGGER trigger_name
   BEFORE UPDATE ON your_table
   FOR EACH ROW
   SET NEW.updated_at = CURRENT_TIMESTAMP;
   //
   DELIMITER ;

2. PostgreSQL:

   -- Method 1: Use a TIMESTAMP column with the DEFAULT statement
   ALTER TABLE your_table
   ALTER COLUMN updated_at SET DEFAULT CURRENT_TIMESTAMP;
   -- Method 2: Use a TRIGGER to update the column on every update
   CREATE OR REPLACE FUNCTION update_updated_at()
   RETURNS TRIGGER AS $$
   BEGIN
    NEW.updated_at = NOW();
    RETURN NEW;
   END;
   $$ LANGUAGE plpgsql;
   CREATE TRIGGER trigger_name
   BEFORE UPDATE ON your_table
   FOR EACH ROW
   EXECUTE FUNCTION update_updated_at();

3. SQL Server:

   -- Method 1: Use a DATETIME column with the DEFAULT statement
   ALTER TABLE your_table
   ADD CONSTRAINT DF_your_table_updated_at
   DEFAULT GETDATE() FOR updated_at;
   -- Method 2: Use a TRIGGER to update the column on every update
   CREATE TRIGGER trigger_name
   ON your_table
   AFTER UPDATE
   AS
   BEGIN
    UPDATE your_table
    SET updated_at = GETDATE()
    FROM your_table
    INNER JOIN inserted ON your_table.primary_key = inserted.primary_key;
   END;

4. SQLite:

   -- Method: Use a TRIGGER to update the column on every update
   CREATE TRIGGER trigger_name
   AFTER UPDATE ON your_table
   FOR EACH ROW
   BEGIN
    UPDATE your_table
    SET updated_at = DATETIME('now')
    WHERE your_table.primary_key = OLD.primary_key;
   END;