使用字符串变量查询字符串连接

Question

我在此查询中遇到问题， 国家是一个变量。 错误：国家/地区列名无效..

cmd.CommandText = "SELECT [news_id], [news_title] from [upload_news] WHERE [city]="+ country;

Answer 1

尝试：

"SELECT [news_id], [news_title] from [upload_news] WHERE [city]='"+ country +"'";

但是如上所示，为select语句添加条件的正确方法是使用变量：

cmd.CommandText = "SELECT [news_id], [news_title] from [upload_news] WHERE [city]=@param"
cmd.Parameters.AddWithValue("param", country); 

PS：您的第一次尝试无法正常运行，因为您执行的实际SQL需要：

SELECT [news_id], [news_title] from [upload_news] WHERE [city] = USA

VS

SELECT [news_id], [news_title] from [upload_news] WHERE [city] = 'USA'