Question

可能重复：
Synchronous database queries with Node.js

通常，我们执行SQL查询并在回调中获取结果。像这样：

sqlExec('SELECT COL FROM TBL;', function (err, results, fields) {
    doSomething(results);
});

但是如果我们需要用SQL结果做更复杂的工作，那么代码会更加丑陋，就像这样：

var tmp = '';
sqlExec('SELECT COL1 FROM TBL1;', function (err, results, fields) {
    tmp = doSomething(results);
    sqlExec('SELECT COL2 FROM TBL2 WHERE CONDITION2 = ' + tmp +  ';', function (err, results, fields) {
        tmp = doSomething2(results);
        sqlExec('SELECT COL3 FROM TBL3 WHERE CONDITION3 = ' + tmp  + ';', function (err, results, fields) {
            ....
        });
    });
});

我们有想法让它同步吗？像这样：

var tmp = '', result = ''; 
result = sqlExec('SELECT COL1 FROM TBL1;');
tmp = doSomething(result);
sqlExec('SELECT COL2 FROM TBL2 WHERE CONDITION2 = ' + tmp  + ';');
tmp = doSomething(result);
sqlExec('SELECT COL3 FROM TBL3 WHERE CONDITION3 = ' + tmp  + ';');
...

谢谢， Gcaufy

Answer 1

这里描述了一个很好的模式http://stella.laurenzo.org/2011/03/bulletproof-node-js-coding/第2段，你的例子就是这样的：

sqlExec('SELECT COL1 FROM TBL1;', function (err, results, fields) {
    var tmp = doSomething(results);
    nextStep( tmp );
}

function nextStep( tmp ) {
    sqlExec('SELECT COL2 FROM TBL2 WHERE CONDITION2 = ' + tmp +  ';', function (err, results, fields) {
    var othertmp = doSomething2(results);
    nextNextStep( othertmp );
    }
}

function nextNextStep( tmp ) {
    sqlExec('SELECT COL3 FROM TBL3 WHERE CONDITION3 = ' + tmp  + ';', function (err, results, fields) {
        ....
 }

现在它几乎看起来像你想要的结果

如何在node.js中执行同步SQL查询

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