pgAdmin4如何连接服务器数据库

本机postgresql服务的话，双击要连接的服务，输入密码。

点击OK，就链接上了。

如果是远程服务器。就在上一节点的server上右键=》create=》server，在d出的界面选择：

connection

然后输入远程服务器的地址，端口，用户名，密码。

看名字就是databasehelper,数据库助手的意思么，这本身就是一个类。

包含了数据库连接，关闭，如果有拓展的话 可能包含基本的数据库JDBC *** 作方法也就是简化增删改查的一些方法。然后，就没有然后了。。。

如果需要的话 百度搜索下就有了，很多改良版本看需求吧。

一般说来 NET里面才叫DBHelper，JAVA里面叫做BaseDao

sql的

using System;

using SystemCollectionsGeneric;

using SystemText;

using SystemDataSqlClient;

using SystemData;

using SystemConfiguration;

namespace DAL

{

public class SqlHelper

{

public static string cons = ConfigurationManagerConnectionStrings["AliCon"]ConnectionString;

/// <summary>

/// one

/// </summary>

/// <param name="sqlcmd">sql</param>

/// <returns>object</returns>

public static object ExeOnlyOne(string sqlcmd)

{

object oRs = null;

using(SqlConnection con = new SqlConnection())

{

conConnectionString = cons;

SqlCommand cmd = new SqlCommand(sqlcmd, con);

conOpen();

oRs = cmdExecuteScalar();

conClose();

}

return oRs;

}

public static object ExeOnlyOne(string sqlcmd,params SqlParameter[] pars)

{

object oRs = null;

using (SqlConnection con = new SqlConnection())

{

conConnectionString = cons;

SqlCommand cmd = new SqlCommand(sqlcmd, con);

cmdParametersAddRange(pars);

conOpen();

oRs = cmdExecuteScalar();

conClose();

}

return oRs;

}

/// <summary>

/// insert update delete

/// </summary>

/// <param name="sqlcmd">sql</param>

/// <returns>int</returns>

public static int ExeCUD(string sqlcmd)

{

int iRs = -1;

using (SqlConnection con = new SqlConnection())

{

conConnectionString = cons;

SqlCommand cmd = new SqlCommand(sqlcmd, con);

conOpen();

iRs = cmdExecuteNonQuery();

conClose();

}

return iRs;

}

public static int ExeCUD(string sqlcmd,params SqlParameter[] pars)

{

int iRs = -1;

using (SqlConnection con = new SqlConnection())

{

conConnectionString = cons;

SqlCommand cmd = new SqlCommand(sqlcmd, con);

cmdParametersAddRange(pars);

conOpen();

iRs = cmdExecuteNonQuery();

conClose();

}

return iRs;

}

/// <summary>

/// all

/// </summary>

/// <param name="sqlcmd">sql</param>

/// <returns>DataTable</returns>

public static DataTable ExeAll(string sqlcmd)

{

DataTable dt = null;

using (SqlConnection con = new SqlConnection())

{

conConnectionString = cons;

SqlDataAdapter sda = new SqlDataAdapter(sqlcmd,con);

DataSet ds = new DataSet();

sdaFill(ds);

dt = dsTables[0];

}

return dt;

}

public static DataTable ExeAll(string sqlcmd,params SqlParameter[] pars)

{

DataTable dt = null;

using (SqlConnection con = new SqlConnection())

{

conConnectionString = cons;

SqlDataAdapter sda = new SqlDataAdapter(sqlcmd, con);

sdaSelectCommandParametersAddRange(pars);

DataSet ds = new DataSet();

sdaFill(ds);

dt = dsTables[0];

}

return dt;

}

/// <summary>

/// all

/// </summary>

/// <param name="sqlcmd">sql</param>

/// <returns>SqlDataReader</returns>

public static SqlDataReader ExeReader(string sqlcmd)

{

SqlConnection con = new SqlConnection();

conConnectionString = cons;

SqlCommand cmd = new SqlCommand(sqlcmd, con);

conOpen();

SqlDataReader sdr = cmdExecuteReader(CommandBehaviorCloseConnection);

return sdr;

}

public static SqlDataReader ExeReader(string sqlcmd,params SqlParameter[] pars)

{

SqlConnection con = new SqlConnection();

conConnectionString = cons;

SqlCommand cmd = new SqlCommand(sqlcmd, con);

cmdParametersAddRange(pars);

conOpen();

SqlDataReader sdr = cmdExecuteReader(CommandBehaviorCloseConnection);

return sdr;

}

}

}

access的

using System;

using SystemData;

using SystemDataOleDb;

using SystemConfiguration;

namespace DAL

{

/// <summary>

/// OLEDBHelper 的摘要说明

/// </summary>

public class OLEDBHelper

{

/// <summary>

/// 连接数据库字符串

/// </summary>

public static string strCon = ConfigurationManagerConnectionStrings["DemoCon"]ConnectionString;

/// <summary>

/// 执行得到一行一列

/// </summary>

/// <param name="sqlText">sql语句</param>

/// <returns>object对象</returns>

public static object ExeOnlyOne(string sqlText)

{

object oRs = null;

using (OleDbConnection con = new OleDbConnection())

{

conConnectionString = strCon;

OleDbCommand cmd = new OleDbCommand();

cmdCommandText = sqlText;

cmdConnection = con;

conOpen();

oRs = cmdExecuteScalar();

conClose();

}

return oRs;

}

/// <summary>

/// 重载ExecuteOnlyOne

/// </summary>

/// <param name="sqlText">命令</param>

/// <param name="pars">参数个数不定</param>

/// <returns></returns>

public static object ExeOnlyOne(string sqlText, params OleDbParameter[] pars)

{

object oRs = null;

using (OleDbConnection con = new OleDbConnection())

{

conConnectionString = strCon;

OleDbCommand cmd = new OleDbCommand();

cmdCommandText = sqlText;

cmdConnection = con;

cmdParametersAddRange(pars);

conOpen();

oRs = cmdExecuteScalar();

conClose();

}

return oRs;

}

/// <summary>

/// 执行Insert update delete语句

/// </summary>

/// <param name="sqlText">sql语句</param>

/// <returns>受影响行数</returns>

public static int ExeCUD(string sqlText)

{

int iRs = 0;

using (OleDbConnection con = new OleDbConnection())

{

conConnectionString = strCon;

OleDbCommand cmd = new OleDbCommand();

cmdCommandText = sqlText;

cmdConnection = con;

conOpen();

iRs = cmdExecuteNonQuery();

conClose();

}

return iRs;

}

/// <summary>

/// 执行带参数的Insert update delete语句

/// </summary>

/// <param name="sqlText">sql语句</param>

/// <param name="pars">参数</param>

/// <returns>受影响行数</returns>

public static int ExeCUD(string sqlText, params OleDbParameter[] pars)

{

int iRs = 0;

using (OleDbConnection con = new OleDbConnection())

{

conConnectionString = strCon;

OleDbCommand cmd = new OleDbCommand();

cmdCommandText = sqlText;

cmdConnection = con;

cmdParametersAddRange(pars);

conOpen();

iRs = cmdExecuteNonQuery();

conClose();

}

return iRs;

}

/// <summary>

/// 查询多条结果

/// </summary>

/// <param name="sqlText">sql语句</param>

/// <returns>DataTable</returns>

public static DataTable ExeAll(string sqlText)

{

DataTable dtRs = null;

using (OleDbConnection con = new OleDbConnection())

{

conConnectionString = strCon;

OleDbDataAdapter sda = new OleDbDataAdapter();

sdaSelectCommand = new OleDbCommand(sqlText, con);

DataSet ds = new DataSet();

sdaFill(ds);

dtRs = dsTables[0];

}

return dtRs;

}

/// <summary>

/// 查询带参的多条结果

/// </summary>

/// <param name="sqlText">sql语句</param>

/// <param name="pars">参数</param>

/// <returns>DataTable</returns>

public static DataTable ExeAll(string sqlText, params OleDbParameter[] pars)

{

DataTable dtRs = null;

using (OleDbConnection con = new OleDbConnection())

{

conConnectionString = strCon;

OleDbDataAdapter sda = new OleDbDataAdapter();

sdaSelectCommand = new OleDbCommand(sqlText, con);

sdaSelectCommandParametersAddRange(pars);

DataSet ds = new DataSet();

sdaFill(ds);

dtRs = dsTables[0];

}

return dtRs;

}

/// <summary>

/// 游标读取数据SqlDataReader

/// </summary>

/// <param name="sqlText">语句</param>

/// <returns>OleDbDataReader</returns>

public static OleDbDataReader ExeReader(string sqlText)

{

OleDbDataReader sdrRs = null;

OleDbConnection con = new OleDbConnection();

conConnectionString = strCon;

OleDbCommand cmd = new OleDbCommand();

cmdConnection = con;

cmdCommandText = sqlText;

conOpen();

sdrRs = cmdExecuteReader(CommandBehaviorCloseConnection);

return sdrRs;

}

/// <summary>

/// 带参reader的sql语句执行

/// </summary>

/// <param name="sqlText">语句</param>

/// <param name="pars">参数</param>

/// <returns>OleDbDataReader</returns>

public static OleDbDataReader ExeReader(string sqlText, params OleDbParameter[] pars)

{

OleDbDataReader sdrRs = null;

OleDbConnection con = new OleDbConnection();

conConnectionString = strCon;

OleDbCommand cmd = new OleDbCommand();

cmdConnection = con;

cmdCommandText = sqlText;

cmdParametersAddRange(pars);

conOpen();

sdrRs = cmdExecuteReader(CommandBehaviorCloseConnection);

return sdrRs;

}

}

}

这里用ContentProvider方法来定义数据库。。

public class AlarmProvider extends ContentProvider //

{

private static final String DB_NAME = "Alarmdb"; //数据库名

private static final int DB_VERSION = 1;//版本号，当程序第一次运行时，数据库被建立，如果

//你更改了数据库，如增加一个表，这时，这个值一般要改一下，这样程序再次安装运行

//时，数据库可自行升级。。如果不改通常要手动删除数据库。。

private static final String ALARM_TABLE_NAME = "alarm"; //一个表名

private static final int ALARM = 1; //与表对应的整数值，相当于id

private static UriMatcher mUriMathcer; //Uri匹配器，建立uri,表名,id三者之间的关系，如下：

static{

mUriMathcer = new UriMatcher(UriMatcherNO_MATCH);

mUriMathceraddURI(AlarmInfoAUTH, "alarm", ALARM);

}

private interface CreateTableInterface //表创建接口

{

public abstract void createAlarmTable(SQLiteDatabase db);

}

//内部类，数据库助手类，并实现表创建接口

private static class DatabaseHelper extends SQLiteOpenHelper implements CreateTableInterface

{

CreateTableInterface mCreateTableInterface = this;

Context mContext = null;

//构造函数，该函数调用后，数据库没有

//创建。。也就是下面的onCreate不会在它调用后就立即调用创建db

public DatabaseHelper(Context context)

{

super(context, DB_NAME, null, DB_VERSION);

// Logi(TAG, "DatabaseHelper be called!");

mContext = context;

}

@Override

public void onCreate(SQLiteDatabase db) //这个方法只在第一次db连接创建db时调用,只一次

{

//create db table

mCreateTableInterfacecreateAlarmTable(db);

}

@Override

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) //db升级时调用

{

// Logi(TAG, "onUpgrade() be called!");

dbexecSQL("DROP TABLE IF EXISTS "+ALARM_TABLE_NAME);

onCreate(db);

}

@Override

public void createAlarmTable(SQLiteDatabase db)

{

// 创建表

dbexecSQL("CREATE TABLE "+ALARM_TABLE_NAME+" ("

+AlarmInfo_ID+" INTEGER PRIMARY KEY,"

+AlarmInfo_LABEL+" TEXT NOT NULL,"

+AlarmInfo_TIME+" TEXT NOT NULL,"

+AlarmInfo_ALERT+" TEXT NOT NULL,"

+AlarmInfo_REPEAT+" TEXT NOT NULL,"

+AlarmInfo_ACTIVE+" TEXT NOT NULL"

+");");

//在表中插入一些数据。。。

dbexecSQL("INSERT INTO "+ALARM_TABLE_NAME+"("+AlarmInfo_LABEL+","

+AlarmInfo_TIME+","+AlarmInfo_ALERT+","

+AlarmInfo_REPEAT+","+AlarmInfo_ACTIVE+

") VALUES('Lunch Alarm','11 : 45 AM','"+TagTONE+"','"+TagEVERY_DAY+"','false');");

dbexecSQL("INSERT INTO "+ALARM_TABLE_NAME+"("+AlarmInfo_LABEL+","

+AlarmInfo_TIME+","+AlarmInfo_ALERT+","

+AlarmInfo_REPEAT+","+AlarmInfo_ACTIVE

+") VALUES('Work Alarm','08 : 45 AM','"+TagTONE+"',"+"'Mon,Tue,Wed,Thu,Fri'"

+",'false');");

dbexecSQL("INSERT INTO "+ALARM_TABLE_NAME+"("+AlarmInfo_LABEL+","

+AlarmInfo_TIME+","+AlarmInfo_ALERT+","+AlarmInfo_REPEAT+","

+AlarmInfo_ACTIVE

+") VALUES('Work Alarm','09 : 00 AM','"+TagTONE+"',"

+"'"+TagWEEKENDS+"','false');");

dbexecSQL("INSERT INTO "+ALARM_TABLE_NAME+"("+AlarmInfo_LABEL+","

+AlarmInfo_TIME+","+AlarmInfo_ALERT+","+AlarmInfo_REPEAT+","

+AlarmInfo_ACTIVE

+") VALUES('Yoga','10 : 15 PM','"+TagTONE+"',"+"'Sun,Wed','false');");

}

}

}

private DatabaseHelper mDatabaseHelper; //定义helper

//以下重写insert,delete,update,query等方法

@Override

public synchronized int delete(Uri uri, String selection, String[] selectionArgs)

{

SQLiteDatabase db = null;

boolean success = false;

int count = 0;

try{

db = mDatabaseHelpergetWritableDatabase();

dbacquireReference();

success = true;

switch(mUriMathcermatch(uri)){

case ALARM:

count = dbdelete(ALARM_TABLE_NAME, selection, selectionArgs);

break;

}

}catch(SQLException e){

eprintStackTrace();

}finally{

if(success == true){

dbreleaseReference();

}

}

return count;

}

@Override

public String getType(Uri uri)

{

switch(mUriMathcermatch(uri)){

case ALARM:

return AlarmInfoCONTENT_TYPE;

default:

throw new IllegalArgumentException("Unknown URI " + uri);

}

}

@Override

public synchronized Uri insert(Uri uri, ContentValues initValues)

{

SQLiteDatabase mSQLiteDatabase = null;

boolean success = false;

try{

mSQLiteDatabase = mDatabaseHelpergetWritableDatabase();

mSQLiteDatabaseacquireReference();

success = true;

long mRowId;

ContentValues values;

if(initValues == null){

values = new ContentValues();

}else{

values = initValues;

}

switch(mUriMathcermatch(uri)){

case ALARM:

mRowId = mSQLiteDatabaseinsert(ALARM_TABLE_NAME,

AlarmInfo_ID, values);

if(mRowId > 0){

return uri;

}else{

throw new SQLException("Failed to insert to "+uri);

}

}

}catch(SQLException e){

eprintStackTrace();

}finally{

if(success == true)

mSQLiteDatabasereleaseReference();

}

return null;

}

@Override

public boolean onCreate()

{

// Logi("alarm provider", "onCreate()");

mDatabaseHelper = new DatabaseHelper(getContext());

return true;

}

@Override

public synchronized Cursor query(Uri uri, String[] projection, String selection,

String[] selectionArgs, String sortOrder)

{

SQLiteQueryBuilder mSQLiteQueryBuilder = new SQLiteQueryBuilder();

switch(mUriMathcermatch(uri)){

case ALARM:

mSQLiteQueryBuildersetTables(ALARM_TABLE_NAME);

break;

}

SQLiteDatabase mSQLiteDatabase = mDatabaseHelpergetWritableDatabase();

mSQLiteDatabaseacquireReference();

Cursor mCursor = mSQLiteQueryBuilderquery(mSQLiteDatabase, projection,

selection, selectionArgs, null, null, sortOrder);

mSQLiteDatabasereleaseReference();

return mCursor;

}

@Override

public synchronized int update(Uri uri, ContentValues values, String selection,

String[] selectionArgs)

{

SQLiteDatabase mSQLiteDatabase = null;

int count = 0;

boolean success = false;

try{

mSQLiteDatabase = mDatabaseHelpergetWritableDatabase();

mSQLiteDatabaseacquireReference();

success = true;

switch(mUriMathcermatch(uri)){

case ALARM:

count = mSQLiteDatabaseupdate(ALARM_TABLE_NAME, values,

selection, selectionArgs);

break;

default:

break;

}

}catch(SQLException e){

eprintStackTrace();

}finally{

if(success == true)

mSQLiteDatabasereleaseReference();

}

return count;

}

}

可以参考android alarm源码，query，update等方法写法基本不改什么，只替换表名。或增加一个case

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