Android中数据库操作以及常用sql

1。创建SQLiteOpenHelper的子类

public class OldDownloadDatabaseHelper extends SQLiteOpenHelper {

private static final int DB_VERSION = 2;

private static final String DB_NAME = "download_info.db";

public static final String TABLE_COUSE_DOWNLOAD_NAME = "download_info"; private static final String SQL_CREATE_DOWNLOAD_TABLE = String.format( "CREATE TABLE %s (_id varchar(255) PRIMARY KEY NOT NULL,supportRanges integer NOT NULL,createAt long NOT NULL,uri varchar(255) NOT NULL,path varchar(255) NOT NULL,size long NOT NULL, progress long NOT NULL,status integer NOT NULL);", TABLE_COUSE_DOWNLOAD_NAME);

public OldDownloadDatabaseHelper(@Nullable Context context) {

super(context, DB_NAME, null, DB_VERSION);

}

@Override public void onCreate(SQLiteDatabase db) {

// 创建数据库1张表 // 通过execSQL（）执行SQL语句（此处创建了1个名为person的表）// String sql = "create table person(id integer primary key autoincrement,name varchar(64),address varchar(64))";// db.execSQL(sql); db.execSQL(SQL_CREATE_DOWNLOAD_TABLE);

}

@Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

}

2.获取可读或者可写的数据库

SQLiteDatabase db =trackHelper.getReadableDatabase();

val helper = OldDownloadDatabaseHelper(AppGlobals.getApplication()).writableDatabase

3.执行SQL语句

/ 查询所有数据

cursor = db.query(OldDownloadTrackDatabaseHelper.TABLE_TRACK_DOWNLOAD_NAME, null, null, null, null, null, null);

4.常用的sql语句

1.模糊删除

helper.execSQL("DELETE FROM download_info where _id like '%" + courseDB.name+"'")

2.删除一张表

val sql ="DROP TABLE IF EXISTS \"ZYREADER\""

db.execSQL(sql)