我如何可以设置SQL查询参数可选? [英] how can i set the parameters for the sql query optional?
问题描述
我建立在ASP.Net Web服务,它发送我的房间列表。
I build a Web Service in ASP.Net which sends me a list of rooms.
该参数是用逗号分隔的ID。
The parameters are id's which are separated by a comma.
我把它们保存到一个字符串,并建立一个SQL SELECT查询。
I saved them to a string and build a sql select query.
当我把所有4个参数我的一切工作正常,我也得到一个结果。但是,当我送不到4我得到一个错误。
When I send all 4 parameters I everything works fine and I get a result. But when I send less then 4 I get an error.
System.Data.SqlClient.SqlException: Incorrect syntax near ')'.
如何设置我的可选在SQL查询中只选择我输入的数值参数?
How can I set my the parameters optional in the sql query to select just the values I entered?
下面是我的code迄今:
Here is my code so far:
internal static List<RAUM> Raum(string RAUMKLASSE_ID, string STADT_ID, string GEBAEUDE_ID, string REGION_ID)
{
List<RAUM> strasseObject = new List<RAUM>();
string raumklasseid = RAUMKLASSE_ID;
string gebaudeid = GEBAEUDE_ID;
string stadtid = STADT_ID;
string regionid = REGION_ID;
using (SqlConnection con = new SqlConnection(@"Data Source=Localhost\SQLEXPRESS;Initial Catalog=BOOK-IT-V2;Integrated Security=true;"))
using (SqlCommand cmd = new SqlCommand(@"SELECT r.BEZEICHNUNG AS BEZEICHNUNG, r.ID AS ID FROM RAUM r WHERE RAUMKLASSE_ID IN (" + raumklasseid + ") AND STADT_ID IN (" + stadtid + ") AND GEBAEUDE_ID IN (" + gebaudeid + ") AND REGION_ID IN (" + regionid + ")", con))
{
con.Open();
using (SqlDataReader rdr = cmd.ExecuteReader())
{
while (rdr.Read())
{
if (rdr["BEZEICHNUNG"] != DBNull.Value && rdr["ID"] != DBNull.Value)
{
strasseObject.Add(new RAUM()
{
RaumName = rdr["BEZEICHNUNG"].ToString(),
RaumID = rdr["ID"].ToString()
});
}
}
}
}
return strasseObject;
}
在此先感谢您的帮助。
Thanks in advance for your help.
推荐答案
想象一下参数 REGION_ID
是一个空字符串。您的查询的那部分将是这样的:
Imagine the parameter REGION_ID
is an empty string. That part of your query will be something like:
...AND REGION_ID IN ()...
由于在键,REGION_ID IN(+ regionid +)
的 regionid
变量将与更换空字符串。这不是有效的SQL语法,所以你会得到例外。
Because in AND REGION_ID IN (" + regionid + ")"
the regionid
variable will be replaced with an empty string. This is not valid SQL syntax so you'll get that exception.
声明一个函数是这样的:
Declare a function like this:
private static void AppendConstrain(StringBuilder query, string name, string value)
{
if (String.IsNullOrWhiteSpace(value))
return;
if (query.Length > 0)
query.Append(" AND ");
query.AppendFormat("{0} IN ({1})", name, value);
}
然后,修改code建立这样的查询:
Then change your code to build the query in this way:
StringBuilder constrains = new StringBuilder();
AppendConstrain(contrains, "RAUMKLASSE_ID", RAUMKLASSE_ID);
AppendConstrain(contrains, "GEBAEUDE_ID", GEBAEUDE_ID);
AppendConstrain(contrains, "STADT_ID", STADT_ID);
AppendConstrain(contrains, "REGION_ID", REGION_ID);
StringBuilder query =
new StringBuilder("SELECT r.BEZEICHNUNG AS BEZEICHNUNG, r.ID AS ID FROM RAUM r");
if (constrains.Length > 0)
{
query.Append(" WHERE ");
query.Append(constrains);
}
using (SqlCommand cmd = new SqlCommand(query.ToString(), con))
{
// Your code...
}
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