Select statment from multiple tables, with variable input

Question

I have two tables: AreaCode and EquipmentNumber.

+------------------------------------+
| AreaCd                             |
|---         


        

Answer 1

I think this is what you are after :

Just added a simple trick;

if(string.IsNullOrEmpty(sNumber))
    sNumber="$$$";               //If sNumber is empty, then selection using sNumber= '$$$' will return nothing.
if(string.IsNullOrEmpty(sType))
    sType="$$$"                 //If sType is empty, then selection using sType = '$$$' will return nothing.
"SELECT Number, Type, Code FROM EqNum, AreaCd " +
"WHERE EqNum.AreaId = AreaCd.AreaId 
AND 
  (Code = " + int nCode + " 
   OR Number = '" + string sNumber + "' 
   OR Type = '" + string sType + "')"

OR using LIKE:

if(string.IsNullOrEmpty(sNumber))
    sNumber="$$$";             //If sNumber is empty, then selection using sNumber LIKE '%$$$%' will return nothing.
if(string.IsNullOrEmpty(sType))
    sType="$$$"                //If sType is empty, then selection using sType LIKE '%$$$%' will return nothing.
"SELECT Number, Type, Code FROM EqNum, AreaCd " +
"WHERE EqNum.AreaId = AreaCd.AreaId 
AND 
  (Code = " + int nCode + "
   OR Number LIKE '%" + string sNumber + "%' 
   OR Type LIKE '%" + string sType + "%')"

See an example at SQL Fiddle