MySQL 字段默认值 一般设null 还是空字符串？

MySQL 字段默认值 一般设null 还是空字符串？设nul 和空字符串的区别是什么，各有什么优缺点。

From [MySQLdiscussion group] 2017-04-17 14:39:43 0  3  987

为什么删除了主键primary之后唯一约束会变成主键约束？

为什么删除了主键primary之后唯一约束会变成主键约束？还有为什么删除不了？必须要有约束们

From [MySQLdiscussion group] 2016-12-21 17:47:37 0  2  987

mysql_replication - What to do if a single writing database cannot meet the performance requirements when mysql reads and writes are separated?

When mysql reads and writes are separated, what should I do if a single writing database cannot meet the perfo...

From [MySQLdiscussion group] 2017-06-20 10:05:42 0  2  985

Please tell me about the high burst operation of the same data.

A table user data is as follows: idnamepassnum1aaa12345602bbb12345633ccc1234564. There is a php file. When exe...

From [MySQLdiscussion group] 2020-10-18 14:25:14 0  1  982

SQL link appears 1130

How to solve the problem of link error 1130

From [MySQLdiscussion group] 2020-02-03 00:50:28 0  1  982

mybatis - Java about Mysql random id generation

I am working on an e-commerce project and encountered a problem when generating the ID. It is definitely not p...

From [MySQLdiscussion group] 2017-05-18 10:44:55 0  3  982

Mysql innodb lock mechanism problem please ask

Why do shared locks and exclusive locks in the same transaction not conflict? Aren't shared locks and exclusiv...

From [MySQLdiscussion group] 2017-06-16 09:19:34 0  2  981

mysql的标签（tag）是如何储存的？

请看这个页面：https://.com/tags可以看到，标签被分类了。是否可以根据这个页面，认定一定有tag_categorys表？还是没有tag_category，只是在前端渲染的时候用了一堆堆的if？或者这个页.....

From [MySQLdiscussion group] 2017-04-17 14:46:34 0  3  981

mysql - 海量的地理位置(经纬度)数据，用什么数据库来存储最好？

数据条数在亿级别。 更新频繁。MySQL无法动态索引。 查询要比建过索引的MySQL的between and 语句快。 最好原生支持空间范围查找。

From [MySQLdiscussion group] 2017-04-17 12:59:58 0  3  981

关于LEFT JOIN 的主表和子表的问题

例如 A LEFT JOIN B 中A是主标还是字表

From [MySQLdiscussion group] 2016-12-20 16:29:27 0  1  980

mysql如果一个事务一直没有commit并且也没有rollback会怎样？

mysql如果一个事务一直没有commit并且也没有rollback会怎样？有什么办法查询到这些没有被commit也没有被rollback的事务。？

From [MySQLdiscussion group] 2017-04-17 13:46:53 0  4  980

mysql - "SELECT 1 UNION SELECT null UNION SELECT !1"的含义

{代码...} 的含义是什么？是选择空集的意思？

From [MySQLdiscussion group] 2017-04-17 11:18:27 0  1  980

mysql - Database storage structure and index issues

Assuming that a node can hold 100 values, then a 3-layer B-tree can hold 1 million data. How do you get 1 mill...

From [MySQLdiscussion group] 2017-06-22 11:54:32 0  1  979

mysql - sql How to query the third-level subset based on the parent id?

Now there is a need to query the third-level subset database based on fid. A table has three fields (id, name,...

From [MySQLdiscussion group] 2017-05-18 10:51:03 0  2  977

MySQL：此种查询结果，怎么仅保留第一条记录？

select id, value from test;查询结果如下id valueyy 123zz 234zz 456 仅想保留id字段的第一条记录，在5.7以下版本中使用"select id, value f...

From [MySQLdiscussion group] 2017-04-17 14:41:39 0  3  976