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Delete terminal history in Linux [closed]
...can use previous commands again. Great feature. However, I started logging mysql into mysql with the sensitive details in the command.
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Can I change a column from NOT NULL to NULL without dropping it?
... I tried with alter column and it didn't work with the latest mysql server. I tried with modify column and it worked. Strange...
– Kostas Andrianos
Aug 19 '17 at 15:29
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常用Sql - 爬虫/数据库 - 清泛IT社区，为创新赋能！
本帖最后由 zqp2013 于 2015-3-17 22:06 编辑
mysql：drop table if exists tablename;
不能写成
drop table tablename if exists tablename;
mysql：建立索引Sql
CREATE TABLE tablename (
`ID` &nbs...
Possible to do a MySQL foreign key to one of two possible tables?
...ut logical XOR is not standard SQL and is not supported by all SQL brands. MySQL has it, but PostgreSQL does not. Oracle has it, but Microsoft does not until 2016. And so on.
– Bill Karwin
Aug 19 '15 at 15:09
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“where 1=1” statement [duplicate]
I saw some people use a statement to query a table in a MySQL database like the following:
10 Answers
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Difference between string and text in rails?
...l is converted into its respective column type in query language.
with MySQL :string is mapped to VARCHAR(255)
- http://guides.rubyonrails.org/migrations.html
:string | VARCHAR | :limit => 1 to 255 (default = 255)
:text | TINYTEXT, TEXT, MEDIUMTEXT, or...
App Inventor 2 SQLite 拓展：超流行兼容主流SQL语法的迷你本地数据库引擎 ...
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SQLite 拓展
SQLite
特性
如何使用
背景
属性
事件
方法
常规
事务
数据操作
绑定参数
案例
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PHP编译configure时常见错误 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...e gmp.h
centos: yum install gmp-devel
14、Configure: error: Cannot find MySQL header files under /usr. Note that the MySQL client library is not bundled anymore!
yum install mysql-devel (For Redhat & Fedora)
# apt-get install libmysql++-dev (For Ubuntu)
15、Configure: error: Please reinstall ...
Cannot issue data manipulation statements with executeQuery()
In MySQL I have two tables, tableA and tableB . I am trying to execute two queries:
10 Answers
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JOIN queries vs multiple queries
... you are joining 3 or more tables on different keys, often databases (i.e. mysql) can only use one index per table, meaning maybe one of the joins will be fast (and use an index) whereas the others will be extremely slow. For multiple queries, you can optimize the indexes to use for each query.
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