在寫SQL中，經(jīng)常會有諸如更新了一行記錄，之后要獲取更新過的這一行。 本身從程序來說，沒啥難度，大不了把這行緩存起來，完了直接訪問。 但是從數(shù)據(jù)庫的角度出發(fā)，怎么能快速的拿出來，而又不對原表進行二次掃描？ 比如其他數(shù)據(jù)庫提供了如下的語法來實現(xiàn)：

返回更新掉的行：

t_girl=#?update?t1?set?log_time?=?now()?where?id?in?(1,2,3)?returning?*;id?|??????????log_time?????????? ----+----------------------------1?|?2014-11-26?11:06:53.5552172?|?2014-11-26?11:06:53.5552173?|?2014-11-26?11:06:53.555217 (3?rows) UPDATE?3 Time:?6.991?ms

返回刪除掉的行：

t_girl=#?delete?from?t1?where?id?<?2?returning?*;id?|??????????log_time?????????? ----+----------------------------1?|?2014-11-26?11:06:53.555217 (1?row) DELETE?1 Time:?6.042?ms

返回插入后的行：

t_girl=#?insert?into?t1?select?1,now()?returning?*;id?|??????????log_time?????????? ----+----------------------------1?|?2014-11-26?11:07:40.431766 (1?row) INSERT?0?1 Time:?6.107?ms t_girl=#

那在MySQL里如何實現(xiàn)呢？?

我可以創(chuàng)建幾張內存表來來保存這些返回值，如下：

CREATE?TABLE?t1_insert?ENGINE?MEMORY?SELECT?*?FROM??t1?WHERE?FALSE; CREATE?TABLE?t1_update?ENGINE?MEMORY?SELECT?*?FROM??t1?WHERE?FALSE; CREATE?TABLE?t1_delete?ENGINE?MEMORY?SELECT?*?FROM??t1?WHERE?FALSE; ALTER?TABLE?t1_insert?ADD?PRIMARY?KEY?(id); ALTER?TABLE?t1_update?ADD?PRIMARY?KEY?(id); ALTER?TABLE?t1_delete?ADD?PRIMARY?KEY?(id);

以上建立了三張表來存放對應的操作。 t1_insert 保存插入；t1_update 保存更新；t1_delete 保存刪除。

那這樣的話，我來創(chuàng)建對應的觸發(fā)器完成。

DELIMITER?$$ USE?`t_girl`$$ DROP?TRIGGER?/*!50032?IF?EXISTS?*/?`tr_t1_insert_after`$$ CREATE/*!50017?DEFINER?=?'root'@'localhost'?*/TRIGGER?`tr_t1_insert_after`?AFTER?INSERT?ON?`t1`?FOR?EACH?ROW?BEGINREPLACE?INTO?t1_insert?VALUES?(new.id,new.log_time);END; $$ DELIMITER?;

DELIMITER?$$ USE?`t_girl`$$ DROP?TRIGGER?/*!50032?IF?EXISTS?*/?`tr_t1_update_after`$$ CREATE/*!50017?DEFINER?=?'root'@'localhost'?*/TRIGGER?`tr_t1_update_after`?AFTER?UPDATE?ON?`t1`?FOR?EACH?ROW?BEGINREPLACE?INTO?t1_update?VALUES?(new.id,new.log_time);END; $$ DELIMITER?;

DELIMITER?$$ USE?`t_girl`$$ DROP?TRIGGER?/*!50032?IF?EXISTS?*/?`tr_t1_delete_after`$$ CREATE/*!50017?DEFINER?=?'root'@'localhost'?*/TRIGGER?`tr_t1_delete_after`?AFTER?DELETE?ON?`t1`?FOR?EACH?ROW?BEGINREPLACE?INTO?t1_delete?VALUES?(old.id,old.log_time);；END; $$ DELIMITER?;

創(chuàng)建好了以上的表和觸發(fā)器后， 拿到返回值就非常容易了， 我直接從以上幾張表來查詢就是。

我現(xiàn)在來演示：

更新：

mysql>?truncate?table?t1_update; Query?OK,?0?rows?affected?(0.00?sec) mysql>?UPDATE?t1?SET?log_time?=?NOW()?WHERE?id?<?15; Query?OK,?3?rows?affected?(0.01?sec) Rows?matched:?3??Changed:?3??Warnings:?0

獲取更新記錄：

mysql>?select?*?from?t1_update; +----+----------------------------+ |?id?|?log_time???????????????????| +----+----------------------------+ |?12?|?2014-11-26?13:38:06.000000?| |?13?|?2014-11-26?13:38:06.000000?| |?14?|?2014-11-26?13:38:06.000000?| +----+----------------------------+ 3?rows?in?set?(0.00?sec)

插入：

mysql>?truncate?table?t1_insert; Query?OK,?0?rows?affected?(0.00?sec) mysql>?INSERT?INTO?t1?VALUES?(1,NOW()); Query?OK,?1?row?affected?(0.08?sec)

獲取插入記錄：

mysql>?select?*?from?t1_insert; +----+----------------------------+ |?id?|?log_time???????????????????| +----+----------------------------+ |??1?|?2014-11-26?13:38:06.000000?| +----+----------------------------+ 1?row?in?set?(0.00?sec)

刪除：

mysql>?truncate?table?t1_delete; Query?OK,?0?rows?affected?(0.00?sec) mysql>?DELETE?FROM?t1?WHERE?id?<?15; Query?OK,?4?rows?affected?(0.01?sec)

獲取刪除記錄：

mysql>?select?*?from?t1_delete; +----+----------------------------+ |?id?|?log_time???????????????????| +----+----------------------------+ |??1?|?2014-11-26?13:38:06.000000?| |?12?|?2014-11-26?13:38:06.000000?| |?13?|?2014-11-26?13:38:06.000000?| |?14?|?2014-11-26?13:38:06.000000?| +----+----------------------------+ 4?rows?in?set?(0.00?sec)

超強干貨來襲 云風專訪：近40年碼齡，通宵達旦的技術人生

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