拼凑SQL字符串

拼接SQL字符串
拼接带有变量的字符串
例如:
"UPDATE Type_Medium_Info SET " + strType_Field + "=' " + strContent + " 'WHERE  Assert_Sn = '" + strAssert_Sn + "' AND Machine_Id= '" + strMachine_Id + "' AND Type_Med_Sn = '" + strType_Med_Sn + "' "