MySQL模拟PostgreSQLgenerate_series表函数

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MySQL模拟PostgreSQLgenerate_series表函数

来源: 作者: 时间:2016-01-30 09:02 【

PostgreSQL 提供了一个很强大的造数据的函数generate_series,基于Common Table Expression。
PostgreSQL 提供了一个很强大的造数据的函数generate_series,基于Common Table Expression。
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。
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:

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)
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