MySQL 没有复杂的应用程序类型,该如何实现这样的功能呢? 我想到的三种方法如下:
1. 用存储过程来做。 缺点是写好多数据库不擅长的应用逻辑。
2. 我们想到MySQL提供了SESSION 变量这样的特性, 可以很方便的完成同样的功能。
3. MariaDB 提供了一种sequence 引擎,也可以方便的做这件事情。
第一种我就不实现了, 我来举例说明后两种。
表结构如下: ytt[love]>show create table test_series; +-------------+-------------------------------------------------------------------------------------------------------------------------+ | Table | Create Table | +-------------+-------------------------------------------------------------------------------------------------------------------------+ | test_series | CREATE TABLE `test_series` ( `id` int(11) NOT NULL, `log_date` date NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1 | +-------------+-------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec) 对应的PostgreSQL 运算结果: t_girl=# insert into test_series select seq, current_date - ‘1 day‘::interval*seq from generate_series(1,20) as g(seq); INSERT 0 20 t_girl=# select * from test_series; id | log_date ----+------------ 1 | 2014-03-02 2 | 2014-03-01 3 | 2014-02-28 4 | 2014-02-27 5 | 2014-02-26 6 | 2014-02-25 7 | 2014-02-24 8 | 2014-02-23 9 | 2014-02-22 10 | 2014-02-21 11 | 2014-02-20 12 | 2014-02-19 13 | 2014-02-18 14 | 2014-02-17 15 | 2014-02-16 16 | 2014-02-15 17 | 2014-02-14 18 | 2014-02-13 19 | 2014-02-12 20 | 2014-02-11 (20 rows)
第一: SESSION 变量。
MySQL 的SESSION 变量来变相实现的话,需要一个种子库。
以下存储过程生成种子库。
DELIMITER $$ USE `t_girl`$$ DROP PROCEDURE IF EXISTS `sp_seed`$$ CREATE DEFINER=`root`@`localhost` PROCEDURE `sp_seed`( IN f_num INT UNSIGNED ) BEGIN DROP TABLE IF EXISTS tmp_seed; CREATE TEMPORARY TABLE tmp_seed (id INT); BEGIN DECLARE i INT; SET i = 1; WHILE i <= f_num DO INSERT INTO tmp_seed VALUES (i); SET i = i + 1; END WHILE; END; END$$ DELIMITER ;
生成20个种子库 ytt[love]>call sp_seed(20); Query OK, 1 row affected (0.15 sec) 现在利用刚才的种子库以及SESSION 变量来实现。 ytt[love]>insert into test_series select @a := @a + 1 as seq, date_sub(current_date(), interval @a day) from tmp_seed,(select @a:=0) as seq; Query OK, 20 rows affected (0.02 sec) Records: 20 Duplicates: 0 Warnings: 0 ytt[love]>select * from test_series; +----+------------+ | id | log_date | +----+------------+ | 1 | 2014-03-02 | | 2 | 2014-03-01 | | 3 | 2014-02-28 | | 4 | 2014-02-27 | | 5 | 2014-02-26 | | 6 | 2014-02-25 | | 7 | 2014-02-24 | | 8 | 2014-02-23 | | 9 | 2014-02-22 | | 10 | 2014-02-21 | | 11 | 2014-02-20 | | 12 | 2014-02-19 | | 13 | 2014-02-18 | | 14 | 2014-02-17 | | 15 | 2014-02-16 | | 16 | 2014-02-15 | | 17 | 2014-02-14 | | 18 | 2014-02-13 | | 19 | 2014-02-12 | | 20 | 2014-02-11 | +----+------------+ 20 rows in set (0.00 sec)
第二:
MySQL(MariaDB ) 提供了一个序列引擎,可以有这样的功能。
由于MySQL 没有表函数功能,所以如果要造多个字段的数据,就得用JOIN来实现了。
ytt[love]>insert into test_series select s1.seq,date_sub(current_date(),interval s2.seq day) as date from seq_1_to_20 as s1, seq_1_to_20 as s2 where s1.seq = s2.seq; Query OK, 20 rows affected (0.07 sec) Records: 20 Duplicates: 0 Warnings: 0 ytt[love]>select * from test_series; +----+------------+ | id | log_date | +----+------------+ | 1 | 2014-03-02 | | 2 | 2014-03-01 | | 3 | 2014-02-28 | | 4 | 2014-02-27 | | 5 | 2014-02-26 | | 6 | 2014-02-25 | | 7 | 2014-02-24 | | 8 | 2014-02-23 | | 9 | 2014-02-22 | | 10 | 2014-02-21 | | 11 | 2014-02-20 | | 12 | 2014-02-19 | | 13 | 2014-02-18 | | 14 | 2014-02-17 | | 15 | 2014-02-16 | | 16 | 2014-02-15 | | 17 | 2014-02-14 | | 18 | 2014-02-13 | | 19 | 2014-02-12 | | 20 | 2014-02-11 | +----+------------+ 20 rows in set (0.00 sec)