获取postgres-query的结果作为Node.js中的变量 [英] Get the result of postgres-query as variable in nodejs

问题描述

我知道以下代码在命令行上显示查询的结果：

I know that the following code prints the result of my query on the command line:

query.on("row", function (row, result) {
  result.addRow(row);
});

query.on("end", function (result, callback) {
    println(JSON.stringify(result))
});

但是，我想在以下代码中将结果值用作变量，而不仅仅是使用它打印到命令行。

However, I want to use the result value in the following code as a variable and not just have it printed out to the command line.

更新：仅能使用下一个查询的值，我希望它不在查询范围之内：

Update: Being able to use the values for the next query is not enough, I want it to be outside of the query scope:

query.on("row", function (row, result) {
  result.addRow(row);
});

query.on("end", function (result, callback) {
    println(JSON.stringify(result))
});
//use the result here

在此先感谢您的回答。

推荐答案

您有2个选择：

• 如果要继续使用基本驱动程序，则必须使用结果回调，然后将其嵌套以便在下一个查询中使用结果：

• If you want to continue using the basic driver, you will have to use the result callback, and then nest those in order to use result in the next query:

connection.query(query1, values1, function(err1, result1) {
    // check if(err1) first, then:
    connection.query(query2, values2, function(err2, result2) {
        // check if(err2) first, then:
        connection.query(query3, values3, function(err3, result3) {
            // check if(err3) first, then:
            cb(result1, result2, result3);        
        });
    });
});

另一种方法是使用promises（ pg-promise ），当您可以像这样链接呼叫时：

The alternative approach is to use promises (pg-promise) when you can chain calls like this:

db.query(query1, values2)
    .then(data => {
        return db.query(query2, values2);
    })
    .then(data => {
        return db.query(query3, values3);
    })
    .catch(error => {});

尽管 pg-promise 在这种情况下是通过方法 task ：

Although the right approach for pg-promise in this case is via method task:

db.task(t => {
    const result = {};
    return t.query(query1, values1)
        .then(data => {
            result.a = data;
            return t.query(query2, values2);
        })
        .then(data => {
            result.b = data;
            return t.query(query3, values3);
        });
        .then(data => {
            result.c = data;
            return result;
        });
})
    .than(data => {
        // data = {a, b, c}
    })
    .catch(error => {});

第二种方法可以让您在执行多个查询时自动访问ES6和ES7的现代语法。时间，您可以这样做：

The second approach automatically gives you access to the modern syntax of ES6 and ES7 when executing multiple queries at a time, as you can do:

对于ES6：

db.task(function * (t) {
    let a = yield t.query(query1, values1);
    let b = yield t.query(query2, values2);
    let c = yield t.query(query3, values3);
    return {a, b, c};
})
    .than(data => {
        // data = {a, b, c}
    })
    .catch(error => {});

对于ES7 / Babel：

For ES7 / Babel:

db.task(async t => {
    let a = await t.query(query1, values1);
    let b = await t.query(query2, values2);
    let c = await t.query(query3, values3);
    return {a, b, c};
})
    .than(data => {
        // data = {a, b, c}
    })
    .catch(error => {});

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