feat: provide support for groupby

Signed-off-by: Muhammad Aaqil <aaqilcs102@gmail.com>

Author: aaqilniz

lib/sql.js

@@ -1439,7 +1439,25 @@ SQLConnector.prototype.buildSelect = function(model, filter, options) {
     }
   }
 
+  let extraSelect = '';
+  if (filter.sum) {
+    extraSelect = `SUM(${filter.sum}) as sumOf${filter.sum}, `;
+  }
+  if (filter.count) {
+    extraSelect += `COUNT(${filter.count}) as countOf${filter.count}, `;
+  }
+  if (filter.avg) {
+    extraSelect += `AVG(${filter.avg}) as avgOf${filter.avg}, `;
+  }
+  if (filter.min) {
+    extraSelect += `MIN(${filter.min}) as minOf${filter.min}, `;
+  }
+  if (filter.max) {
+    extraSelect += `MAX(${filter.max}) as maxOf${filter.max}, `;
+  }
+
   let selectStmt = new ParameterizedSQL('SELECT ' +
+    extraSelect +
     this.buildColumnNames(model, filter) +
     ' FROM ' + this.tableEscaped(model));
 
@@ -1449,6 +1467,10 @@ SQLConnector.prototype.buildSelect = function(model, filter, options) {
       selectStmt.merge(whereStmt);
     }
 
+    if (filter.groupBy) {
+      selectStmt.merge(this.buildGroupBy(filter.groupBy));
+    }
+
     if (filter.order) {
       selectStmt.merge(this.buildOrderBy(model, filter.order));
     }
@@ -1510,7 +1532,13 @@ SQLConnector.prototype.all = function find(model, filter, options, cb) {
     }
 
     const objs = data.map(function(obj) {
-      return self.fromRow(model, obj);
+      const object = self.fromRow(model, obj);
+      if (obj[`sumOf${filter.sum}`]) { object[`sumOf${filter.sum}`] = obj[`sumOf${filter.sum}`]; }
+      if (obj[`countOf${filter.count}`]) { object[`countOf${filter.count}`] = obj[`countOf${filter.count}`]; }
+      if (obj[`avgOf${filter.avg}`]) { object[`avgOf${filter.avg}`] = obj[`avgOf${filter.avg}`]; }
+      if (obj[`minOf${filter.min}`]) { object[`minOf${filter.min}`] = obj[`minOf${filter.min}`]; }
+      if (obj[`maxOf${filter.max}`]) { object[`maxOf${filter.max}`] = obj[`maxOf${filter.max}`]; }
+      return object;
     });
     if (filter && filter.include) {
       self.getModelDefinition(model).model.include(