sql基本语句返回值类型

矫情吗；* 2022-09-24 07:28 29阅读 0赞

**备注：可以通过返回值判断是否添加成功**  
db.insert==>long（当添加到几行就返回几行，因为行数可能很大所以用long）

db.updata==>int

db.rawquery==>cursor(while循环添加到list)

db.delete==>int

db.execSQL==>void

**下面代码具体使用情况：**

package com.db.util;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Vector;
    
    import android.database.Cursor;
    import android.database.sqlite.SQLiteDatabase;
    import android.util.Log;
    import android.widget.EditText;
    
    public class DBUtil
    {
        
        static SQLiteDatabase sld;
        public static void createOrOpenDatabase() throws Exception
        {
            sld=SQLiteDatabase.openDatabase
            (
                    "/data/data/com.db/dbtest", //数据库所在路径
                    null,                                 //CursorFactory
                    SQLiteDatabase.OPEN_READWRITE|SQLiteDatabase.CREATE_IF_NECESSARY //读写、若不存在则创建
            );            
            String sql0="create table if not exists user(username varchar2(20),password varchar2(20))";
            sld.execSQL(sql0); 
        }
    
        public static void closeDatabase() throws Exception
        {
           try
           {
               sld.close(); 
           }
           catch(Exception e)
           {
               e.printStackTrace();
           }
        }
    
        /*=====================================begin==========================================================*/
        //获取用户信息-winxiang
        public static List<String> searchuser(String username){
            List<String> list=new ArrayList<String>();
            try
            {
                createOrOpenDatabase();
                String sql="select * from user where username='"+username+"'";
                Cursor cur=sld.rawQuery(sql, new String[]{});
                while(cur.moveToNext())
                {
                    list.add(cur.getString(0));  //username
                    list.add(cur.getString(1));  //password 
                }
                cur.close();
                closeDatabase();
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }
            return list;        
        }
      //获取所有用户信息-winxiang
        public static List<String> searchalluser(){
            List<String> list=new ArrayList<String>();
            try
            {
                createOrOpenDatabase();
                String sql="select * from user";
                Cursor cur=sld.rawQuery(sql, new String[]{});
                while(cur.moveToNext())
                {
                    list.add(cur.getString(0));  //username
                    list.add(cur.getString(1));  //password 
                }
                cur.close();
                closeDatabase();
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }
            return list;        
        }
    
        public static void updatetable(String sql)
        {
            try
            {
                createOrOpenDatabase();            
                sld.execSQL(sql);            
                closeDatabase();
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }
        }
    
        //舍弃user表
        public static void droptable(){
            try
            {
                String sql="drop table user";
                createOrOpenDatabase();            
                sld.execSQL(sql);            
                closeDatabase();
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }
            Log.d("DB","had deleted table: user->");  
        }
        /*=====================================end==========================================================*/
    }