你如何使用MySql IN子句

我试图弄清楚如何在ASP.NET C＃中使用MySql In cluse。 这是我的代码

var WebSites = string.Join(",", wsl.Select(x => "'" + x.DomainUrl + "'").ToArray()); string q = "select Id, Url, Title, Date, ImageUrl from post where WebSiteUrl IN (@Url)"; 

当我不使用参数时，此代码有效。 当我包含参数时，我得不到查询的结果。

这是我的参数代码

 cmd.Parameters.Add("@Urls", MySqlDbType.Text).Value = WebSites; 

这是完整的代码

  public static IList FindPostsByWebSiteList(IEnumerable wsl) { var pl = new List(); var WebSites = string.Join(",", wsl.Select(x => "'" + x.DomainUrl + "'").ToArray()); string q = "select Id, Url, Title, Date, ImageUrl from post where WebSiteUrl IN (@Urls)"; using (MySqlConnection con = new MySqlConnection(WebConfigurationManager.ConnectionStrings["MySqlConnectionString"].ToString())) { using (MySqlCommand cmd = new MySqlCommand(q, con)) { cmd.Parameters.Add("@Urls", MySqlDbType.Text).Value = WebSites; con.Open(); var reader = cmd.ExecuteReader(CommandBehavior.CloseConnection); while (reader.Read()) { var p = new Post(); p.Id = reader.GetInt32("Id"); p.Url = reader.GetString("Url"); p.Title = reader.GetString("Title"); p.Date = reader.GetDateTime("Date"); p.ImageUrl = reader.GetString("ImageUrl"); pl.Add(p); } return pl; } } } 

Answer 1

您引用了@Url而不是@Urls

也许你的问题只是一个错字

Answer 2

我找到了答案。 这里是

  public static IList FindPostsByWebSiteList(string[] urls) { var pl = new List(); var urlArray = urls.Select((x,y) => "@url" + y.ToString()).ToArray(); var urlsJoined = string.Join(",", urlArray); string q = string.Format("select Id, Url, Title, Date, ImageUrl from post where WebSiteUrl IN ({0})", urlsJoined); using (MySqlConnection con = new MySqlConnection(WebConfigurationManager.ConnectionStrings["MySqlConnectionString"].ToString())) { using (MySqlCommand cmd = new MySqlCommand(q, con)) { for (int x = 0; x < urlArray.Length; x++) { cmd.Parameters.Add(urlArray[x], MySqlDbType.Text).Value = urls[x]; } con.Open(); var reader = cmd.ExecuteReader(CommandBehavior.CloseConnection); while (reader.Read()) { var p = new Post(); p.Id = reader.GetInt32("Id"); p.Url = reader.GetString("Url"); p.Title = reader.GetString("Title"); p.Date = reader.GetDateTime("Date"); p.ImageUrl = reader.GetString("ImageUrl"); pl.Add(p); } return pl; } } } 

Answer 3

IN语句应该期望一个字符串数组，并且您传递一个字符串

你的最终SQL看起来像这样：

 select Id, Url, Title, Date, ImageUrl from post where WebSiteUrl IN ('url1,url2,url3') 

代替

 select Id, Url, Title, Date, ImageUrl from post where WebSiteUrl IN ('url1', 'url2', 'url3') 

检查这个问题：

将List 添加到mysql参数