void

mysql 自增序列(轉)

1:原理是在建立一個觸發器TRIGGER tri_NewBH  在table插入時執行序列計算 mysql> CREATE TABLE tb(BH CHAR(16),content VARCHAR(20),`date` DATETIME,val INT); Query OK, 0 rows affected (0.05 sec)  mysql> mysql> mysql> DELIMITER $$ mysql> DROP TRIGGER IF EXISTS tri_NewBH $$ Query OK, 0 rows affected, 1 warning (0.00 sec)  mysql> mysql> CREATE TRIGGER tri_NewBH BEFORE INSERT ON tb     -> FOR EACH ROW     -> BEGIN -> DECLARE dt CHAR(8);     -> DECLARE bh_id CHAR(16);     -> DECLARE number INT;     -> DECLARE new_bh VARCHAR(16);     -> -> SET dt = DATE_FORMAT(CURDATE(),'%Y%m%d');     -> -> SELECT -> MAX(BH) INTO bh_id     -> FROM tb     -> WHERE BH LIKE CONCAT(dt,'%');     -> -> IF bh_id = '' OR bh_id IS NULL THEN -> SET new_bh = CONCAT(dt,'00000001');     -> ELSE -> SET number = RIGHT(bh_id,8) + 1;     -> SET new_bh = RIGHT(CONCAT('00000000',number),8);     -> SET new_bh=CONCAT(dt,new_bh);     -> END IF;     -> -> SET NEW.BH = new_bh;     -> END$$ Query OK, 0 rows affected (0.09 sec)  mysql> mysql> DELIMITER ; mysql> INSERT INTO tb(content,`date`,val) VALUES('LiangCK','2009-05-11',20); Query OK, 1 row affected (0.00 sec)  mysql> INSERT INTO tb(content,`date`,val) VALUES('LiangCK','2009-05-11',20); Query OK, 1 row affected (0.01 sec)  mysql> INSERT INTO tb(content,`date`,val) VALUES('LiangCK','2009-05-11',20); Query OK, 1 row affected (0.00 sec)  mysql> INSERT INTO tb(content,`date`,val) VALUES('LiangCK','2009-05-11',20); Query OK, 1 row affected (0.00 sec)  mysql> INSERT INTO tb(content,`date`,val) VALUES('LiangCK','2009-05-11',20); Query OK, 1 row affected (0.00 sec)  mysql> INSERT INTO tb(content,`date`,val) VALUES('LiangCK','2009-05-11',20); Query OK, 1 row affected (0.01 sec)  mysql> INSERT INTO tb(content,`date`,val) VALUES('LiangCK','2009-05-11',20); Query OK, 1 row affected (0.00 sec)  mysql> SELECT * FROM tb; +------------------+---------+---------------------+------+ | BH               | content | date                | val  | +------------------+---------+---------------------+------+ | 2009051100000001 | LiangCK | 2009-05-11 00:00:00 | 20 | | 2009051100000002 | LiangCK | 2009-05-11 00:00:00 | 20 | | 2009051100000003 | LiangCK | 2009-05-11 00:00:00 | 20 | | 2009051100000004 | LiangCK | 2009-05-11 00:00:00 | 20 | | 2011051200000001 | LiangCK | 2009-05-11 00:00:00 | 20 | | 2011051200000002 | LiangCK | 2009-05-11 00:00:00 | 20 | | 2011051200000003 | LiangCK | 2009-05-11 00:00:00 | 20 | +------------------+---------+---------------------+------+ 7 rows in set (0.00 sec) 
 

2.下面就是另外一個的實現方案: 

原理是創建一個專門記錄序列的表sequence,記錄有當前序列號,序列的間隔如+1

Sql代碼  

1. DROP TABLE IF EXISTS sequence;/*創建記錄當前序列的表*/  
2. CREATE TABLE sequence (  
3. name              VARCHAR(50) NOT NULL,  
4. current_value INT NOT NULL,  
5. increment       INT NOT NULL DEFAULT 1,  
6. PRIMARY KEY (name)  
7. ) ENGINE=InnoDB;  
8. INSERT INTO sequence VALUES ('MovieSeq',3,5);  
9. DROP FUNCTION IF EXISTS currval;  
10. DELIMITER $/*創建一個獲取當前序列的function*/  
11. CREATE FUNCTION currval (seq_name VARCHAR(50))  
12. RETURNS INTEGER  
13. CONTAINS SQL  
14. BEGIN  
15.   DECLARE value INTEGER;  
16.   SET value = 0;  
17.   SELECT current_value INTO value  
18.   FROM sequence  
19.   WHERE name = seq_name;  
20.   RETURN value;  
21. END$  
22. DELIMITER ;  

 測試一下結果：

Sql代碼  

1. mysql> SELECT currval('MovieSeq');  
2. +---------------------+  
3. | currval('MovieSeq') |  
4. +---------------------+  
5. |                   3 |  
6. +---------------------+  
7. 1 row in set (0.00 sec)  
8. mysql> SELECT currval('x');  
9. +--------------+  
10. | currval('x') |  
11. +--------------+  
12. |            0 |  
13. +--------------+  
14. 1 row in set, 1 warning (0.00 sec)  
15. mysql> show warnings;  
16. +---------+------+------------------+  
17. | Level   | Code | Message          |  
18. +---------+------+------------------+  
19. | Warning | 1329 | No data to FETCH |  
20. +---------+------+------------------+  
21. 1 row in set (0.00 sec)  

 nextval 

//獲取下一個數值..先在sequence里面調用update當前最大數值+1然后再調用currval獲得當前數值

Sql代碼  

1. DROP FUNCTION IF EXISTS nextval;  
2. DELIMITER $  
3. CREATE FUNCTION nextval (seq_name VARCHAR(50))  
4. RETURNS INTEGER  
5. CONTAINS SQL  
6. BEGIN  
7.    UPDATE sequence  
8.    SET          current_value = current_value + increment  
9.    WHERE name = seq_name;  
10.    RETURN currval(seq_name);  
11. END$  
12. DELIMITER ;  

 mysql> select nextval('MovieSeq');

Sql代碼  

1. +---------------------+  
2. | nextval('MovieSeq') |  
3. +---------------------+  
4. |                  15 |  
5. +---------------------+  
6. 1 row in set (0.09 sec)  
7.   
8. mysql> select nextval('MovieSeq');  
9. +---------------------+  
10. | nextval('MovieSeq') |  
11. +---------------------+  
12. |                  20 |  
13. +---------------------+  
14. 1 row in set (0.01 sec)  
15.   
16. mysql> select nextval('MovieSeq');  
17. +---------------------+  
18. | nextval('MovieSeq') |  
19. +---------------------+  
20. |                  25 |  
21. +---------------------+  
22. 1 row in set (0.00 sec)  

 setval 

Sql代碼  

1. DROP FUNCTION IF EXISTS setval;  
2. DELIMITER $  
3. CREATE FUNCTION setval (seq_name VARCHAR(50), value INTEGER)  
4. RETURNS INTEGER  
5. CONTAINS SQL  
6. BEGIN  
7.    UPDATE sequence  
8.    SET          current_value = value  
9.    WHERE name = seq_name;  
10.    RETURN currval(seq_name);  
11. END$  
12. DELIMITER ;  

 mysql> select setval('MovieSeq',150);

Sql代碼  

1. +------------------------+  
2. | setval('MovieSeq',150) |  
3. +------------------------+  
4. |                    150 |  
5. +------------------------+  
6. 1 row in set (0.06 sec)  
7.   
8. mysql> select curval('MovieSeq');  
9. +---------------------+  
10. | currval('MovieSeq') |  
11. +---------------------+  
12. |                 150 |  
13. +---------------------+  
14. 1 row in set (0.00 sec)  
15.   
16. mysql> select nextval('MovieSeq');  
17. +---------------------+  
18. | nextval('MovieSeq') |  
19. +---------------------+  
20. |                 155 |  
21. +---------------------+  
22. 1 row in set (0.00 sec)  

 

posted on 2015-04-29 17:33 void 閱讀(899) 評論(0)  編輯  收藏 所屬分類: MySql 、Hibernate