Question

我想创建一个MySQL程序插入表中并删除其他表...

我的程序：

Python

错误讯息：insert ignore into old_events (select * from events where start < now()); delete from events where start < now();

Answer 1

使用INSERT INTO SELECT时删除()：

insert ignore into old_events 
select * 
from `events` 
where `start` < now();

考虑使用列列表而不是*：

insert ignore into old_events(col1, col2, ...) 
select col1, col2, ... 
from `events` 
where `start` < now();

请记住，now()与时间有关，您应将其结果存储在变量中以进行比较。在INSERT和DELETE now()之间可能会发生变化。

Answer 2

当我看到您插入查询时，您将数据插入old_events列，但您从事件表中选择所有列。因此，您只能选择要插入old_events列的列

INSERT IGNORE INTO old_events 
SELECT * FROM events 
WHERE start < now();

DELETE FROM events WHERE start < now();

在我的系统中，我创建了两个表

create table events( id int,event_name varchar(20), start timestamp default current_timestamp);
create table old_events( id int,event_name varchar(20), start timestamp default current_timestamp);

然后将6行插入events表

insert into events(id,event_name, start) values 
(1,'event1','2016-02-18'),
(2,'event2','2016-02-19'),
(3,'event3','2016-02-20'),
(4,'event4','2016-02-21'),
(5,'event5','2016-02-22'),
(6,'event6','2016-02-23');

并执行select query，其中start小于current time

SELECT * FROM events 
WHERE start < now();

返回5行 see example

但是在sqlfiddle中，我们只能运行select查询，所以在我的系统中执行以下查询并成功执行并且将5行插入到old_events中，其中start小于current time

INSERT INTO old_events
SELECT * 
FROM EVENTS WHERE START < NOW();

之后，我从old_events表中选择行，返回5行

select * from old_events;

之后我执行删除查询并从事件表中删除5行

DELETE FROM EVENTS WHERE START < NOW();

在所有步骤之后，我执行另外两个查询，从events and old_events table

中选择

select * from events;  // its return 1 row where start is greater than now()
select * from old_events; // its return 5 row where start is less than now()

MySQL程序插入和删除

2 个答案: