node.js 操作 postgresql 數據庫

上一篇node.js訪問postgresql數據庫，主要是在同一個文件裏面實現對數據庫的操作。

這篇node.js操作postgresql數據庫，採用的是兩個文件的方式實現，一個文件相當於客戶端，實現連接數據庫，調用相應的函數，而另一個文件是具體實現函數的。

在你安裝了node.js，postgresql數據庫（不一定是本機）和相應的模塊的基礎上，在數據庫中建表teacher。並插入幾條測試數據，這兒插入的測試數據爲：

create table teacher(id varchar(10),name varchar(20),pwd varchar(10));

insert into teacher values('1','aaa','111');
insert into teacher values('2','bbb','222');
insert into teacher values('3','ccc','333');
insert into teacher values('4','ddd','444');

1) client.js

var f = require('./function');
var pg = require('pg');

var conString = "tcp://postgres:postgres@localhost/my";

var client = new pg.Client(conString);

var value = ['10','fillp','abc'];
insertSQLString = 'insert into teacher values($1,$2,$3)';
selectSQLString = 'select * from teacher';
updateSQLString = "update teacher set NAME='ipone' where ID='4'";
deleteSQLString = "delete from teacher where ID='10'";

client.connect(function(error, results) {
    if(error){
        console.log('ClientConnectionReady Error: ' + error.message);
        client.end();
        return;
    }
    console.log('Connecting to postgres...');
    console.log('Connected to postgres automatically.');
    console.log('connection success...\n');

    f._select(client,selectSQLString);
    f._insert(client,insertSQLString,value);
    f._select(client,selectSQLString);
    f._delete(client,deleteSQLString);
});

2) function.js

function _insert(client,insertSQLString,value)
{
    console.log("insert beginning");
    client.query(insertSQLString, value,  function(error, results)
    {
        if(error)
        {
            console.log("ClientReady Error: " + error.message),
            client.end();
            return;
        }
        console.log('Inserted: ' + results.affectedRows + ' row.'),
        console.log('insert success...\n');
    });
    console.log("insert end\n");
}

function _select(client,selectSQLString)
{
    console.log("select beginning");
    client.query(selectSQLString,  function selectCb(error, results, fields)
    {
        console.log("in select callback function");
        if (error)
        {
            console.log('GetData Error: ' + error.message),
            client.end();
            return;
        }
        if(results.rowCount > 0)
        {
            var firstResult,
            resultSet = '';
            for(var i = 0, len = results.rowCount; i < len; i++)
            {
                firstResult = results.rows[i]; 
                resultSet += 'id:' + firstResult['id'] + ' ' + 'name:' + firstResult['name'] + ' ' + 
                             'pwd:' + firstResult['pwd'] + '\n'; 
            }
        }
        console.log(resultSet);
        /* 添加功能：使查詢結果集返回到客戶端並保證此函數的通用性. */
    });
    console.log("select end\n");
}

function _update(client,updateSQLString)
{
    console.log("update beginning");
    client.query(updateSQLString,function(error, results)
    {
        if(error)
        {
            console.log("ClientReady Error: " + error.message),
            client.end();
            return;
        }
        console.log('update success...\n');
    });
    console.log("update end\n");
}

function _delete(client,deleteSQLString)
{
    console.log("delete beginning");
    client.query(deleteSQLString,  function(error, results)
    {
        if(error)
        {
            console.log("ClientReady Error: " + error.message),
            client.end();
            return;
        }
        console.log('delete success...\n');
    });
    console.log("delete end\n");
}


exports._insert = _insert;
exports._select = _select;
exports._update = _update;
exports._delete = _delete;

3) 運行node client.js,結果如下：

Connecting to postgres...
Connected to postgres automatically.
connection success...

select beginning
select end

insert beginning
insert end

select beginning
select end

delete beginning
delete end

in select callback function
id:1 name:aaa pwd:111
id:2 name:bbb pwd:222
id:3 name:ccc pwd:333
id:4 name:ddd pwd:444

Inserted: undefined row.
insert success...

in select callback function
id:1 name:aaa pwd:111
id:2 name:bbb pwd:222
id:3 name:ccc pwd:333
id:4 name:ddd pwd:444
id:10 name:fillp pwd:abc

delete success...

在函數實現裏面，我們採用了回調函數的形式實現，根據輸出信息可以很號的看出node.js的主要特性：非阻塞