使用Node.js操作postgresql数据库

上一篇node.js访问postgresql数据库，主要是在同一个文件里面实现对数据库的操作。

这篇node.js操作postgresql数据库，采用的是两个文件的方式实现，一个文件相当于客户端，实现连接数据库，调用相应的函数，而另一个文件是具体实现函数的。

在你安装了node.js，postgresql数据库（不一定是本机）和相应的模块的基础上，在数据库中建表teacher。并插入几条测试数据，这儿插入的测试数据为：

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：使查询结果集返回到客户端并保证此函数的通用性. */
    });
    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) 运行node client.js,结果如下：

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...

在函数实现里面，我们采用了回调函数的形式实现，根据输出信息可以很号的看出node.js的主要特性：非阻塞