Android 持久化存贮之 SQLite

Android SQLite 数据库操作

对于 数据库的操作

创建数据库和表

1. 首先 写一个用来操作数据库的 DB 类,使用单例模式

public static RadishStudyDB getInstance(Context context) {
        if (m_radishStudyDB == null) {
            m_radishStudyDB = new RadishStudyDB(context);
        }
        return m_radishStudyDB;
    }

1. 在DB 类中 写一个私有的 实现 SQLiteOpenHelper的数据库帮助类,并在DB类的 构造函数中实例化,并且获取SQLiteDatabase 对象,操作数据库 都是这个对象来操作的.同时写一个 关闭 SQLiteDatabase 对象的 函数,在退出app的时候关闭数据库.当第一次调用函数 getWritableDatabase( ) 或者 getReadableDatabase()函数的时候才会执行 onCreate()创建表,函数onUpgrade()升级数据库的时候会调用.

DB的构造函数
public RadishStudyDB(Context context) {
        m_radishStudyOpenHelper = new StudentOpenHelper(context, DB_NAME, null, m_version);
        m_radishStudydb = m_radishStudyOpenHelper.getWritableDatabase();
    }

创建表的Sql语句:
private static String create_TABLE_STUDENT = "create table " + TABLE_NAME_STUDENT
            + " (_id integer not null primary key autoincrement,"
            + "name text,"
            + "number integer,"
            + "age integer)";


private class StudentOpenHelper extends SQLiteOpenHelper {
        private int m_version = 1;

        public StudentOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
            super(context, name, factory, version);
            this.m_version = version;
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL(create_TABLE_STUDENT);
            Log.i(TAG, "创建数据库,或表");
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.i(TAG, "数据库 更新");
        }
    }

public void clossDB() {
        if (m_radishStudydb.isOpen()) {
            m_radishStudydb.close();
        }
    }

到此为止,数据库和表都创建完毕.

删除数据库

context.deleteDatabase("DB_NAME");

对于 表的操作

创建 表 在SQLiteOpenHelper 的 onCreate()方法中 创建

,数据库第一次执行函数 getWritableDatabase( ) 或者 getReadableDatabase()函数的时候才会执行onCreate()方法,真正创建表.

使用SQL语句创建

public void createTable(String tableName,String _id,String name,String number,String age){
        String CREATE_TABLE = "create table " + tableName
                + " ("+_id+" integer not null primary key autoincrement,"
                + name+" text,"
                + number+" integer,"
                + age+" integer)";
        m_radishStudydb.execSQL(CREATE_TABLE);
    }

查询表是否存在 的两种方法(我知道到的)

查询 Sqlite_master

public boolean sqlTableIsExist(String tableName) {
        boolean result = false;
        try {
            String sql = "select count(*) as c from Sqlite_master  where type ='table' and name ='" + tableName.trim() + "' ";
            Cursor cursor = m_radishStudydb.rawQuery(sql, null);
            if (cursor.moveToNext()) {
                int count = cursor.getInt(0);
                if (count > 0) {
                    result = true;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }

使用 函数 query()查询,如果没有表,则会报异常

public boolean sqlTableIsExist(String tableName) {
        boolean result = false;
        try {
            Cursor query = m_radishStudydb.query(tableName, null, null, null, null, null, null);
            if (query != null) {
                result = true;
            }
        } catch (Exception e) {
            e.printStackTrace();
            Log.i("RadishStudyDB","e ------------------- ");
        }

        return result;
    }

查询表中所有字段

public String[] getAllTableLine(String tableName) {
        String[] columnNames = null;
        try {
            Cursor cursor = m_radishStudydb.query(tableName, null, null, null, null, null, null);
            columnNames = cursor.getColumnNames();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return columnNames;
    }

查询表中字段是否存在

public boolean sqlTableFieldIsExist(String tableName,String type) {
        boolean result = false;
        try {
            Cursor cursor = m_radishStudydb.query(tableName, null, null, null, null, null, null);
            int count = cursor.getColumnIndex(type); //返回 -1 表示不存在
            if (count >= 0) {
                result = true;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }

添加表中的字段 (alter 只能重命名和添加字段)

public boolean addLine(String insertColumnTable,String lineName) {
        boolean databasePath = false;
        try {
            String ADD_LINE = "alter table "+insertColumnTable+" add column "+lineName+" text ";
            m_radishStudydb.execSQL(ADD_LINE);
        } catch (SQLException e) {
            e.printStackTrace();
            return databasePath;
        }
        databasePath = sqlTableFieldIsExist(insertColumnTable, lineName);
        return databasePath;
    }

删除表中的字段

修改表中的字段

重命名表的名称

public boolean renameTable(String oldTableName,String newTableName) {
        boolean databasePath = false;
        try {
            String ADD_LINE = "alter table "+oldTableName+" rename to "+newTableName;
            m_radishStudydb.execSQL(ADD_LINE);
        } catch (SQLException e) {
            e.printStackTrace();
            return databasePath;
        }
        databasePath = sqlTableIsExist2(newTableName);
        return databasePath;
    }

复制表

创建一张新表,复制另一张表的数据

public boolean copyTable(String oldTableName, String newTableName) {
        //创建一张表并且拷贝另一张表的数据
        boolean databasePath = false;
        try {
            String COPY_TABLE2 = "create table "+newTableName+" as select _id, number , name ,age from "+oldTableName;
            String COPY_TABLE3 = "create table "+newTableName+" as select _id, number , name ,age from "+oldTableName +" where number = '222'";
            m_radishStudydb.execSQL(COPY_TABLE2);
        } catch (SQLException e) {
            e.printStackTrace();
            return databasePath;
        }
        databasePath = sqlTableIsExist2(newTableName);
        return databasePath;
    }

从一张表中复制数据到另一张表

public void copyTable2(String oldTableName, String newTableName) {
        //创建一张表并且拷贝另一张表的数据

        try {
            String COPY_TABLE2 = "insert into "+newTableName+" select _id, number , name ,age from "+oldTableName;
            String COPY_TABLE3 = "insert table "+newTableName+"  select _id, number , name ,age from "+oldTableName +" where number = '222'";

            m_radishStudydb.execSQL(COPY_TABLE2);
        } catch (SQLException e) {
            e.printStackTrace();
        }        
 }

删除表

public boolean deleteTable(String tableName) {
        boolean databasePath = false;
        try {
            String DELETE_TABLE = "drop table "+tableName;
            m_radishStudydb.execSQL(DELETE_TABLE);
        } catch (SQLException e) {
            e.printStackTrace();
            return databasePath;
        }
        databasePath = sqlTableIsExist2(tableName);
        return !databasePath;
    }

对于表中 数据 的操作

添加记录

用insert()函数

public long addRecord (StudentBean studentBean){
        ContentValues values = new ContentValues();
        values.put("name",studentBean.getName());
        values.put("number",studentBean.getNumber());
        values.put("age",studentBean.getAge());
        long insert = m_radishStudydb.insert(TABLE_NAME_STUDENT, null, values);
        return insert;
    }

用SQL语句 insert

public void addRecordSQL (StudentBean studentBean){
        String ADD_RECORD = "insert into "+TABLE_NAME_STUDENT+"( name,number,age) values ('"
                +studentBean.getName()+"',"
                +studentBean.getNumber()+","
                +studentBean.getAge()+")";
        m_radishStudydb.execSQL(ADD_RECORD);
    }

用SQL语句 insert 从另一张表中复制数据添加记录

 public void addRecordSQLFromTable (String table){
        String ADD_RECORD = "insert into "+table+" select _id, number,name,age from "+TABLE_NAME_STUDENT+" where number = 11 and name = 'jhk'";
        m_radishStudydb.execSQL(ADD_RECORD);
    }

查询记录

查询所有记录

public LinkedList<StudentBean> queryAllRecord(String tableName) {
        LinkedList<StudentBean> studentBeenList = new LinkedList<>();
        try {
            Cursor cursor = m_radishStudydb.query(tableName, null, null, null, null, null, null);
            if (cursor != null) {
                while (cursor.moveToNext()){
                    StudentBean studentBean = new StudentBean();
                    studentBean.set_id(cursor.getInt(cursor.getColumnIndex("_id")));
                    studentBean.setName(cursor.getString(cursor.getColumnIndex("name")));
                    studentBean.setNumber(cursor.getInt(cursor.getColumnIndex("number")));
                    studentBean.setAge(cursor.getInt(cursor.getColumnIndex("age")));
                    studentBeenList.add(studentBean);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return studentBeenList;
    }

按条件查询记录

public LinkedList<StudentBean> queryAllRecord2(String tableName,int id) {
        LinkedList<StudentBean> studentBeenList = new LinkedList<>();
        try {
            Cursor cursor = m_radishStudydb.query(tableName, null, "_id = "+id, null, null, null, null);
            if (cursor != null) {
                while (cursor.moveToNext()){
                    StudentBean studentBean = new StudentBean();
                    studentBean.set_id(cursor.getInt(cursor.getColumnIndex("_id")));
                    studentBean.setName(cursor.getString(cursor.getColumnIndex("name")));
                    studentBean.setNumber(cursor.getInt(cursor.getColumnIndex("number")));
                    studentBean.setAge(cursor.getInt(cursor.getColumnIndex("age")));
                    studentBeenList.add(studentBean);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return studentBeenList;
    }

更新记录

删除记录