如何在 Oracle 中临时存储数据以供后续使用?
oraclesoftware & codingprogramming
问题:
您想临时存储 SQL 的结果。
解决方案
我们可以使用 CREATE GLOBAL TEMPORARY TABLE 语句创建一个表，用于临时存储会话数据。此外，您还可以指定是否将临时表数据保留至会话结束，还是保留至事务提交。我们可以进一步使用 ON COMMIT PRESERVE ROWS 子句来指定在用户会话结束时删除的数据。
示例
CREATE GLOBAL TEMPORARY TABLE tmp_players ON COMMIT PRESERVE ROWS AS SELECT * FROM players WHERE coach_id IS NOT NULL;
全局临时表存储会话私有数据，这些数据仅在会话期间存在。一旦创建临时表，它将一直存在，直到我们将其删除。
示例
select table_name, temporary from user_tables WHERE temporary = 'Y'; TMP_PLAYERS Y
当我们在临时表中创建记录时，系统会在默认临时表空间中分配空间。我们可以通过运行以下 SQL 语句来验证这一点。
示例
SELECT username, contents, segtype FROM v$sort_usage;
为了提高表的性能，我们可以创建索引并在会话结束时删除它们。
最后，我们可以使用 ON COMMIT DELETE ROWS 子句来指示数据应在会话结束时删除。以下示例解释了相同的原理。
示例
CREATE GLOBAL TEMPORARY TABLE tmp_players ON COMMIT DELETE ROWS AS SELECT * FROM players WHERE coach_id IS NOT NULL;
数据准备:本题所用数据如下所示。
示例
DROP TABLE players; COMMIT; CREATE TABLE players ( player_rank NUMBER(6) , first_name VARCHAR2(20) , last_name VARCHAR2(25) CONSTRAINT player_last_name_nn NOT NULL , email VARCHAR2(30) CONSTRAINT player_email_nn NOT NULL , phone_number VARCHAR2(20) , player_start_date DATE CONSTRAINT player_start_date_nn NOT NULL , title_id VARCHAR2(20) CONSTRAINT player_title NOT NULL , prize_money NUMBER(8,2) , coach_id NUMBER(6) , CONSTRAINT player_email UNIQUE (email) ) ;
示例
INSERT INTO players VALUES (1,'Roger','Federer','roger.federer@notreal.com','111.111.1234',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'AUS_OPEN','350000',1);
INSERT INTO players VALUES (2,'Rafa','Nadal','Rafa.Nadal@notreal.com','111.111.1235',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'FRENCH_OPEN','300000',1);
INSERT INTO players VALUES (3,'Andy','Murray','Andy.Murray@notreal.com','111.111.1236',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'WIMBELDON','450000',1);
INSERT INTO players VALUES (4,'Stan','Wawrinka','Stan.Wawrinka@notreal.com','111.111.1237',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'FRENCH_OPEN','300000',2);
INSERT INTO players VALUES (5,'Dominic','Theim','Dominic.Theim@notreal.com','111.111.1238',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'US_OPEN','500000',2);
INSERT INTO players VALUES (6,'Novak','Djokovic','Novak.Djokovic@notreal.com','111.111.1239',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'AUS_OPEN','350000',2);
INSERT INTO players VALUES (7,'Andy','Zverev','Andy.Zverev@notreal.com','111.111.1240',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'FRENCH_OPEN','300000',2);
INSERT INTO players VALUES (8,'Andy','Rublev','Andy.Rublev@notreal.com','111.111.1241',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'WIMBELDON','450000',3);
INSERT INTO players VALUES (9,'Janik','Sinner','Janik.Sinner@notreal.com','111.111.1242',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'FRENCH_OPEN','300000',3);
INSERT INTO players VALUES (10,'Danil','Medvedev','Danil.Medvedev@notreal.com','111.111.1243',TO_DATE('17-06-2003', 'dd-MM-yyyy'),'US_OPEN','500000',3);
COMMIT;
