如何检查数据库表中是否存在值 [英] how to check if a value exists in DB table

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问题描述

如何检查数据库表中是否存在值,并将布尔值返回给vb.net中的变量?

how to check if a value exists in a DB table and return a Boolean value to variable in vb.net??

推荐答案

这并执行功能以获取所需的输出

you can create a function like this and execute the function to get your desired output

create function fnCheckExists()
returns bit
as
begin
declare @val as bit=0;
if exists (select yourColumn from yourTable)
begin
 set @val=1;
end
else
begin
 set @val=0;
end
return @val
end


像这样尝试

Hi Try like this

private void Form4_Load(object sender, EventArgs e)
      {
          int Company_Id = 3;
          Boolean id = Convert.ToBoolean(existCompanyId(Company_Id));
      }

public int existCompanyId(int Company_Id)
{
 
 string SQLConnectionStr = "Password=password;Connection Timeout=0;Persist Security
   Info=False;User ID=userid;Initial Catalog=databasename;Data Source=servername;";
 SqlConnection sqlConnection = new SqlConnection(SQLConnectionStr);
 int CId;

 string TableExists = "IF EXISTS (select * from Company WHERE CompanyId ='" +  
 Company_Id + "') select 1 ELSE select 0";
            
try
  {
   using (SqlConnection spContentConn = new SqlConnection(SQLConnectionStr))
  {
   spContentConn.Open();
   using (SqlCommand TableExistsQry = new SqlCommand(TableExists, spContentConn))
   {
    TableExistsQry.CommandTimeout = 0;
    TableExistsQry.CommandType = CommandType.Text;
    CId = System.Convert.ToInt32(TableExistsQry.ExecuteScalar());
   }
     spContentConn.Close();
  }
    return CId;
 }
 catch (Exception ex)
  {
   throw ex;
  }
}



如果表中存在公司ID 3,我们将获得ID为true的ID,否则将获得其他明智的ID的false.



If the Company Id 3 exists in the table we will get id as true other wise id as false.


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