MySQL程序插入和刪除

Question

我想創建一個MySQL過程以插入表中並從另一個表中刪除...

我的程序：

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

錯誤消息： insert ignore into old_events (select * from events where start < now()); delete from events where start < now(); insert ignore into old_events (select * from events where start < now()); delete from events where start < now();

Answer 1

使用INSERT INTO SELECT時刪除() ：

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

考慮使用列列表而不是* ：

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

請記住， now()是與時間相關的，您應將其結果存儲在變量中以進行比較。 在INSERT和DELETE之間， now()可能會更改。

Answer 2

如我所見，您將查詢插入到old_events列中，但您從事件表中選擇了所有列。 因此您只能選擇要插入到old_events列中的那列

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

DELETE FROM events WHERE start < now();

在我的系統中，我創建了兩個表

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);

然后將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');

我執行開始current time小於current time選擇查詢

SELECT * FROM events 
WHERE start < now();

返回5行， 請參見示例

但是在sqlfiddle中，我們只能運行select查詢，因此在我的系統中執行以下查詢之后，它會成功執行，並將5行插入到old_events中，其中start小於current time

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

之后，我從old_events表中選擇行，其返回5行

select * from old_events;

之后，我執行刪除查詢並將其從事件表中刪除5行

DELETE FROM EVENTS WHERE START < NOW();

在所有步驟之后，我events and old_events table從events and old_events table執行兩個查詢選擇

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()