标签: sqlite

如果我有大量的SQLite数据库,都具有相同的模式,那么将它们合并在一起以便对所有数据库执行查询的最佳方法是什么？

我知道可以使用ATTACH来执行此操作,但它具有32和64个数据库的限制,具体取决于计算机上的内存系统.

我尝试在带有Ruby 1.8.6,Rails 2.2.2,gem 1.3和sqlite-3.5.9的Fedora 9 Linux机器上安装SQLite gem.这是我正在运行的命令及其结果:

sudo gem install sqlite3-ruby
Building native extensions.  This could take a while...
ERROR:  Error installing sqlite3-ruby:
    ERROR: Failed to build gem native extension.

/usr/bin/ruby extconf.rb install sqlite3-ruby
can't find header files for ruby.

Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/sqlite3-ruby-1.2.4 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/sqlite3-ruby-1.2.4/ext/sqlite3_api/gem_make.out

gem_make.out只重复已发送到控制台的内容.我该如何安装这个宝石？

在MySQL中我可以使用RAND()函数,在SQLite 3中有没有其他选择？

我想要做的就是按字母顺序抓住这些东西并忽略大写字母.

db.rawQuery("SELECT " + catName + " FROM "+tableName+" ORDER BY "+catName+" ASC COLLATE NOCASE;", null);

这是我上面使用的代码,但它总是给我一个SQLite异常,说COLLATE是一个语法错误.

android.database.sqlite.SQLiteException:near"COLLATE":语法错误:,同时编译:SELECT Artist FROM testTable COLLATE NOCASE ASC

我有几个sqlite数据库文件.我想知道数据库文件版本,即数据库是使用sqlite2或sqlite3还是任何其他主/子版本(不是sqlite库或驱动程序或user_version或schema_version)创建的.

我在遵循Android中使用SQLite 的指南时遇到了麻烦.我正在使用a ListFragment而不是ListActivity(如示例中所示),所以我使用了ListFragment工具LoaderManager.LoaderCallbacks<Cursor>.然后,在以下fillData()方法中ListFragment:

private void fillData() {
    // Fields from the database (projection)
    // Must include the _id column for the adapter to work
    String[] from = new String[] { NotesSQLiteHelper.COLUMN_TITLE };
    // Fields on the UI to which we map
    int[] to = new int[] { R.id.label };

    getLoaderManager().initLoader(0, null, this); //error
    adapter = new SimpleCursorAdapter(getApplicationContext(), R.layout.notes_row, null, from, to, 0);
    setListAdapter(adapter);
}

我收到错误:

The method …

我有关于HDF5性能和并发性的以下问题:

1. HDF5是否支持并发写访问？
2. 除了并发性考虑外,HDF5在I/O性能方面的表现如何(压缩率是否会影响性能)？
3. 由于我在Python中使用HDF5,它的性能与Sqlite相比如何？

参考文献:

• http://www.sqlite.org/faq.html#q5
• 可以在NFS文件系统上锁定sqlite文件吗？
• http://pandas.pydata.org/

如何在CREATE TABLE语句中索引列？表格看起来像

command.CommandText =
    "CREATE TABLE if not exists file_hash_list( " +
        "id    INTEGER PRIMARY KEY, " +
        "hash  BLOB NOT NULL, " +
        "filesize INTEGER NOT NULL);";
command.ExecuteNonQuery();

我希望filesize是索引,并希望它是4个字节

以降序显示数据的最有效方法是什么？

public String getRank() {

    String[] rank = new String[]{ KEY_ROWID };
    Cursor c = scoreDb.query(DATABASE_TABLE, rank, null, null, null, null, null);   //reading information from db.
    String rankResult = "";

    int iRow = c.getColumnIndex(KEY_ROWID); //Cursor looking for column setting equal to these ints.


    for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) { 
        //Move to first row - where cursor starts and moves to next row as long it is not after last row.
        rankResult = rankResult + c.getString(iRow) + "\n"; 
        //Returning value of row …

我正在使用Ubuntu并在使用db:migrate for ruby​​项目时遇到问题.

rails aborted!
LoadError: Error loading the 'sqlite3' Active Record adapter. Missing a gem it depends on? can't activate sqlite3 (~> 1.3.6), already activated sqlite3-1.4.0. Make sure all dependencies are added to Gemfile.
/home/juan/odin_on_rails/RailsaAPP/bin/rails:9:in `<top (required)>'
/home/juan/odin_on_rails/RailsaAPP/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'

Caused by:
Gem::LoadError: can't activate sqlite3 (~> 1.3.6), already activated sqlite3-1.4.0. Make sure all dependencies are added to Gemfile.
/home/juan/odin_on_rails/RailsaAPP/bin/rails:9:in `<top (required)>'
/home/juan/odin_on_rails/RailsaAPP/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'
Tasks: TOP => db:migrate => db:load_config …