Question

我在运行Node的JS中构建一个简单的API。它连接到MS SQL DB以获取文章并将其作为JSON返回。这一切都很完美，但我觉得我可以更简单地编写查询。

目前我有几个if语句。有没有办法使查询动态，所以我不必为每个查询都有一个if语句？

...

app.get('/articles', function (req, res) {

    // Our URL parameters
    var articles = req.query.articles;
    var countryID = req.query.countryID;
    var offset = req.query.offset;

    // Set up the database connection
    var connection = new sql.Connection(db_config, function(err) {

        // Log any errors to the console
        if (err) console.log(err);

        // Connect using prepared statement
        var ps = new sql.PreparedStatement(connection);

        // Our variable is an Int
        ps.input('articles', sql.Int);
        ps.input('countryID', sql.Int);
        ps.input('offset', sql.Int);
        ps.input('live', sql.VarChar(5));

        // Build the query and pass in the parameters

        // @articles, @countryID and @offset are empty
        if (isEmpty(articles) && isEmpty(countryID) && isEmpty(offset)) {
            var query = 'SELECT TOP 15 * FROM dbo.articlesCountryTown WHERE articleLive = (@live) ORDER BY PublishDate DESC';
            //console.log('Using query 1');

        // @articles and @offset are empty, @countryID is present
        } else if (isEmpty(articles) && countryID && isEmpty(offset)) {
            var query = 'SELECT TOP 15 * FROM dbo.articlesCountryTown WHERE CntryId = (@countryID) AND articleLive = (@live) ORDER BY PublishDate DESC';
            //console.log('Using query 2');

        // @articles is present, @countryID and @offset are empty
        } else if (articles && isEmpty(countryID) && isEmpty(offset)) {
            var query = 'SELECT TOP (@articles) * FROM dbo.articlesCountryTown WHERE articleLive = (@live) ORDER BY PublishDate DESC';
            //console.log('Using query 3');

        // @articles and @countryID are empty, @offset is present
        } else if (isEmpty(articles) && isEmpty(countryID) && offset) {
            var query = 'SELECT TOP 15 * FROM (select *, ROW_NUMBER() OVER (ORDER BY PublishDate DESC) as r_n_n from dbo.articlesCountryTown WHERE articleLive = (@live)) xx WHERE r_n_n >= (@offset + 1)';
            //console.log('Using query 4');

        // @articles and @countryID are present, @offset is empty
        } else if (articles && countryID && isEmpty(offset)) {
            var query = 'SELECT TOP (@articles) * FROM dbo.articlesCountryTown WHERE CntryId = (@countryID) AND articleLive = (@live) ORDER BY PublishDate DESC';
            //console.log('Using query 5');

        // @articles and @offset are present, @countryID is empty
        } else if (articles && isEmpty(countryID) && offset) {
            var query = 'SELECT TOP (@articles) * FROM (select *, ROW_NUMBER() OVER (ORDER BY PublishDate DESC) as r_n_n from dbo.articlesCountryTown WHERE articleLive = (@live)) xx WHERE r_n_n >= (@offset + 1)';
            //console.log('Using query 6');

        // @articles, @countryID and @offset are all present
        } else {
            var query = 'SELECT TOP (@articles) * FROM (select *, ROW_NUMBER() OVER (ORDER BY PublishDate DESC) as r_n_n from dbo.articlesCountryTown WHERE CntryId = (@countryID) AND articleLive = (@live)) xx WHERE r_n_n >= (@offset + 1)';
            //console.log('Using query 7');
        }

        // Prepare the query
        ps.prepare(query, function(err) {
            // Log any errors to the console
            if (err) console.log(err);

            // Pass in the parameters and execute the query
            ps.execute({articles: req.query.articles, countryID: req.query.countryID, offset: req.query.offset, live: 'true'}, function(err, recordset) {
                // Return the JSON
                res.json(recordset);

                // Close the connection
                ps.unprepare(function(err) {
                    // Log any errors to the console
                    if (err) console.log(err);
                });
            });
        });
    });
});

...

Answer 1

如果你能够将空值传递给@ article，@ countryId和@offset，那么只需一个查询就可以了：

SELECT TOP (ISNULL(@articles, 15)) * FROM (
    SELECT *, ROW_NUMBER() OVER (ORDER BY PublishDate DESC) as r_n_n from dbo.articlesCountryTown 
    WHERE CntryId = CASE WHEN @countryId IS NULL THEN CntryId ELSE @countryId END
    AND articleLive = (@live)
) xx 
WHERE r_n_n >= (ISNULL(@offset, 0) + 1)

更好的是，将其包装到存储过程中，参数默认为null。使用存储过程总是比在服务器级别使用字符串更好。

Answer 2

尝试节点模块 node-mysql 。 node-mysql module link

有一种格式方法可以帮助您创建和执行动态查询。
它将返回可以转换为json数据的对象。

示例：

DB.format('select * from users where id = ?' [userId]);

Javascript Node API构建SQL查询的最佳方式

2 个答案: