title: Using Alasql can you replace null column with empty string
body: <p>In my angular controller i have ExportToExcel function, which is using alasql to export data to Excel and the data is coming from angular array. 
  <strong>The issue is the array might contains null as data, is it a way to replace null to empty string in alasql</strong> </p>
  
  <p>Following is the function</p>
  
  <pre><code> ac.ExportToExcel = function () {
          var time = new Date().toJSON().slice(0, 10);
          alasql('SELECT * INTO XLSX("ExchangeReport' + time + '.xlsx",{headers:true}) FROM ? WHERE BillingPeriod = "' + ac.ExchangeReport.BillingPeriod + '" or "' + ac.ExchangeReport.BillingPeriod + '" = "" ', [ac.ExchangeDatas]);
      }
  </code></pre>
  
  <p>And this is my data source</p>
  
  <pre><code>ac.ExchangeDatas = [];
  </code></pre>
  
  <p>from</p>
  
  <pre><code>        ac.GetAllExchangeData = function () {
          AccountRepository.GetAllExchangeData().$promise.then(
              function (data) {
                  ac.ExchangeDatas = data.result;
              },
              function (err) {
                  console.log("error in GetAllExchangeData : " + err);
              }
          );
      }
  </code></pre>
  
  <p>Data in excel:</p>
  
  <p><a href="https://i.stack.imgur.com/dzipM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dzipM.png" alt="enter image description here"></a></p>