如何解决MySQL存储时间类型挑选的问题
发布时间：2022-02-10 06:36:04 所属栏目：MySql教程 来源：互联网
导读：这篇文章主要为大家展示了如何解决MySQL存储时间类型选择的问题，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下如何解决MySQL存储时间类型选择的问题这篇文章吧。 MySQL中存储时间通常会用datetime类型，但现在
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这篇文章主要为大家展示了“如何解决MySQL存储时间类型选择的问题”，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下“如何解决MySQL存储时间类型选择的问题”这篇文章吧。 MySQL中存储时间通常会用datetime类型，但现在很多系统也用int存储unix时间戳，它们有什么区别？本人总结如下： int （1）4个字节存储，INT的长度是4个字节，存储空间上比datatime少，int索引存储空间也相对较小，排序和查询效率相对较高一点点 （2）可读性极差，无法直观的看到数据 TIMESTAMP （1）4个字节储存 （2）值以UTC格式保存 （3）时区转化 ，存储时对当前的时区进行转换，检索时再转换回当前的时区。 （4）TIMESTAMP值不能早于1970或晚于2037 datetime （1）8个字节储存 （2）与时区无关 （3）以'YYYY-MM-DD HH:MM:SS'格式检索和显示DATETIME值。支持的范围为'1000-01-01 00:00:00'到'9999-12-31 23:59:59' 随着Mysql性能越来越来高，个人觉得关于时间的存储方式，具体怎么存储看个人习惯和项目需求吧 分享两篇关于int vs timestamp vs datetime性能测试的文章 Myisam:MySQL DATETIME vs TIMESTAMP vs INT 测试仪 CREATE TABLE `test_datetime` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `datetime` FIELDTYPE NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM; 机型配置 kip-locking key_buffer = 128M max_allowed_packet = 1M table_cache = 512 sort_buffer_size = 2M read_buffer_size = 2M read_rnd_buffer_size = 8M myisam_sort_buffer_size = 8M thread_cache_size = 8 query_cache_type = 0 query_cache_size = 0 thread_concurrency = 4 测试 DATETIME 14111 14010 14369 130000000 TIMESTAMP 13888 13887 14122 90000000 INT 13270 12970 13496 90000000 执行mysql mysql> select * from test_datetime into outfile ‘/tmp/test_datetime.sql'; Query OK, 10000000 rows affected (6.19 sec) mysql> select * from test_timestamp into outfile ‘/tmp/test_timestamp.sql'; Query OK, 10000000 rows affected (8.75 sec) mysql> select * from test_int into outfile ‘/tmp/test_int.sql'; Query OK, 10000000 rows affected (4.29 sec) alter table test_datetime rename test_int; alter table test_int add column datetimeint INT NOT NULL; update test_int set datetimeint = UNIX_TIMESTAMP(datetime); alter table test_int drop column datetime; alter table test_int change column datetimeint datetime int not null; select * from test_int into outfile ‘/tmp/test_int2.sql'; drop table test_int; So now I have exactly the same timestamps from the DATETIME test, and it will be possible to reuse the originals for TIMESTAMP tests as well. mysql> load data infile ‘/export/home/ntavares/test_datetime.sql' into table test_datetime; Query OK, 10000000 rows affected (41.52 sec) Records: 10000000 Deleted: 0 Skipped: 0 Warnings: 0 mysql> load data infile ‘/export/home/ntavares/test_datetime.sql' into table test_timestamp; Query OK, 10000000 rows affected, 44 warnings (48.32 sec) Records: 10000000 Deleted: 0 Skipped: 0 Warnings: 44 mysql> load data infile ‘/export/home/ntavares/test_int2.sql' into table test_int; Query OK, 10000000 rows affected (37.73 sec) Records: 10000000 Deleted: 0 Skipped: 0 Warnings: 0 As expected, since INT is simply stored as is while the others have to be recalculated. Notice how TIMESTAMP still performs worse, even though uses half of DATETIME storage size. Let's check the performance of full table scan: mysql> SELECT SQL_NO_CACHE count(id) FROM test_datetime WHERE datetime > ‘1970-01-01 01:30:00′ AND datetime < ‘1970-01-01 01:35:00′; +———–+ | count(id) | +———–+ | 211991 | +———–+ 1 row in set (3.93 sec) mysql> SELECT SQL_NO_CACHE count(id) FROM test_timestamp WHERE datetime > ‘1970-01-01 01:30:00′ AND datetime < ‘1970-01-01 01:35:00′; +———–+ | count(id) | +———–+ | 211991 | +———–+ 1 row in set (9.87 sec) mysql> SELECT SQL_NO_CACHE count(id) FROM test_int WHERE datetime > UNIX_TIMESTAMP('1970-01-01 01:30:00′) AND datetime < UNIX_TIMESTAMP('1970-01-01 01:35:00′); +———–+ | count(id) | +———–+ | 211991 | +———–+ 1 row in set (15.12 sec) Then again, TIMESTAMP performs worse and the recalculations seemed to impact, so the next good thing to test seemed to be without those recalculations: find the equivalents of those UNIX_TIMESTAMP() values, and use them instead: mysql> select UNIX_TIMESTAMP('1970-01-01 01:30:00′) AS lower, UNIX_TIMESTAMP('1970-01-01 01:35:00′) AS bigger; +——-+——–+ | lower | bigger | +——-+——–+ | 1800 | 2100 | +——-+——–+ 1 row in set (0.00 sec) mysql> SELECT SQL_NO_CACHE count(id) FROM test_int WHERE datetime > 1800 AND datetime < 2100; +———–+ | count(id) | +———–+ | 211991 | +———–+ 1 row in set (1.94 sec) Innodb:MySQL DATETIME vs TIMESTAMP vs INT performance and benchmarking with InnoDB 以上是“如何解决MySQL存储时间类型选择的问题”这篇文章的所有内容，感谢各位的阅读！ （编辑：拼字网 - 核心网） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |
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