How to query max value in map layer field

Question

I have a web application with a Query widget that is pointing to a REST service point layer. The layer is NOT in the map, and will only display the results of a query. The users will be able to perform a spatial query on the layer, but first I want to filter the data via an SQL expression or esri QueryTask so that only a subset of the data is available for the spatial query, if this makes any sense. I can't do a definition query in the mxd because the data get updated regularly, so this needs to be dynamic. Basically I want to look at all of the numbers in a particular field, find the largest number (or most recent batch) and use that number to plug in to the SQL Expression in the TaskSetting.js file (or if there is an SQL property that would do the same thing at the time of the query). This way, when the user performs the spatial query, they will only be querying the latest batch numbers and not the entire dataset. I tried using QueryTask, but this returns feature sets, not the value, and I can't seem to figure out if there is a way to set the where statement to filter out all features except the ones with the highest value in the "Batch" field. I can hard code the expression with the correct value (see line 19), but then I have to update the value every time the data is updated on the server! _getWhereInfo: function(){ var result = { status: 0, where: "" }; if(this.askForValues){ var newExpr = this.filterParams.getFilterExpr(); var validExpr = newExpr && typeof newExpr === 'string'; if(validExpr){ result.status = 1; result.where = newExpr; }else{ result.status = -1; result.where = null; } }else{ result.status = 1; //result.where = this.currentAttrs.config.filter.expr; result.where = "Batch = 20"; //value hard coded //console.log("where expression ", result.where); } if(result.status === 1 && !result.where){ result.where = "1=1"; } return result; },‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ I tried using "Batch = Max(Batch)" and a few variations, but no luck so far! Maybe I am going about this all wrong?

RobertScheitlin__GISP · Accepted Answer

Franklin,

In the jimu folder there is statisticsUtils.js that will allow you to get statistics from a field like MAX. Look at the getStatisticsResult function and there it will show you the properties of the params object it is expecting.