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java中的缓存技术该如何实现 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...时需要谨慎.第四个环节,数据库中也可以有缓存, 比如说mysql的querycache.
那么也就是说在整个请求流程的任何一点,我们都可以加缓存.但是是所有的数据都可以放进缓存的吗.当然不是,需要放进缓存的数据总是有一些特征的,要清...
How do I view the SQLite database on an Android device? [duplicate]
I have a set of data in an SQLite database. I need to view the database on a device. How do I do that?
19 Answers
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Laravel Schema onDelete set null
...to set proper onDelete constraint on a table in Laravel. (I'm working with SqLite)
4 Answers
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Postgresql - change the size of a varchar column to lower length
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There's a description of how to do this at Resize a column in a PostgreSQL table without changing data. You have to hack the database catalog data. The only way to do this officially is with ALTER TABLE, and as you've noted that change will lock and rewrite the entire table while it's running....
Dump a mysql database to a plaintext (CSV) backup from the command line
I'd like to avoid mysqldump since that outputs in a form that is only convenient for mysql to read. CSV seems more universal (one file per table is fine). But if there are advantages to mysqldump, I'm all ears. Also, I'd like something I can run from the command line (linux). If that's a mysql s...
How to set a default value for a datetime column to record creation time in a migration?
...the model will set the current time in the model.
You can also place some sql code in the migration for setting the default value at the database level, something like:
execute 'alter table foo alter column starts_at set default now()'
Setting something like this:
create_table :foo do |t|
t.d...
connecting to MySQL from the command line
How can you connect to MySQL from the command line in a Mac? (i.e. show me the code)
6 Answers
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Is there any performance gain in indexing a boolean field?
...an index, if you have too many records it doesn't use the index anyways.
MySQL not using index when checking = 1 , but using it with = 0
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How should I store GUID in MySQL tables?
...char 16 binary? not char? not binary? I dont see that type in any of the mysql gui tools, nor any documentation in mysql site. @BillyONeal
– nawfal
Jun 24 '12 at 19:41
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How do I get the MIN() of two fields in Postgres?
...essions evaluate to NULL.
Note that GREATEST and LEAST are not in the SQL standard, but are a common extension. Some other databases make them return NULL if any argument is NULL, rather than only when all are NULL...
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