如何在触发器中声明变量，因为MySQL在“where子句”中说未知列“”id_productos“”。“”

CREATE TRIGGER trigger_name
AFTER INSERT ON table_name
FOR EACH ROW

CREATE TRIGGER trigger_name
AFTER INSERT ON table_name
FOR EACH ROW
BEGIN
    -- 在这里声明变量和执行其他逻辑
END;

CREATE TRIGGER trigger_name
AFTER INSERT ON table_name
FOR EACH ROW
BEGIN
    DECLARE variable_name data_type DEFAULT initial_value;
    -- 在这里执行其他逻辑
END;

CREATE TRIGGER trigger_name
AFTER INSERT ON table_name
FOR EACH ROW
BEGIN
    DECLARE variable_name data_type DEFAULT initial_value;
    -- 在这里使用变量
    SET variable_name = new.column_name;
END;