Implement SQL-99 ROW_NUMBER() OVER (PARTITION BY) syntax for per-group row numbering

src/40select.js

@@ -190,6 +190,7 @@ yy.Select = class Select {
 		// todo?: 3. Compile SELECT clause
 		// For ROWNUM()
 		query.rownums = [];
+		query.grouprownums = [];
 
 		this.compileSelectGroup0(query);
 
@@ -371,6 +372,46 @@ yy.Select = class Select {
 					}
 				}
 
+				// Handle GROUP_ROW_NUMBER() and ROW_NUMBER() OVER (PARTITION BY ...) - restart numbering when grouping column(s) change
+				if (query.grouprownums && query.grouprownums.length > 0) {
+					for (var j = 0, jlen = query.grouprownums.length; j < jlen; j++) {
+						var config = query.grouprownums[j];
+						var partitionColumns;
+
+						// Determine which columns to partition by
+						if (config.partitionColumns && config.partitionColumns.length > 0) {
+							// Use explicit PARTITION BY columns
+							partitionColumns = config.partitionColumns;
+						} else {
+							// Fall back to first column for GROUP_ROW_NUMBER()
+							var columnKeys = Object.keys(res[0] || {});
+							partitionColumns = [columnKeys[0]];
+						}
+
+						var prevValues = null;
+						var rowNum = 0;
+
+						for (var i = 0, ilen = res.length; i < ilen; i++) {
+							// Get current partition key (combination of all partition columns)
+							var currentValues = partitionColumns
+								.map(function (col) {
+									return res[i][col];
+								})
+								.join('|');
+
+							// Reset counter when partition changes
+							if (i === 0 || currentValues !== prevValues) {
+								rowNum = 1;
+							} else {
+								rowNum++;
+							}
+
+							res[i][config.as] = rowNum;
+							prevValues = currentValues;
+						}
+					}
+				}
+
 				var res2 = modify(query, res);
 
 				if (cb) {

src/424select.js

@@ -416,7 +416,22 @@ yy.Select.prototype.compileSelectGroup0 = function (query) {
 				col.funcid &&
 				(col.funcid.toUpperCase() === 'ROWNUM' || col.funcid.toUpperCase() === 'ROW_NUMBER')
 			) {
-				query.rownums.push(col.as);
+				// Check if this has OVER clause with PARTITION BY
+				if (col.over && col.over.partition) {
+					// Window function with partition - track for post-processing
+					query.grouprownums.push({
+						as: col.as,
+						partitionColumns: col.over.partition.map(function (p) {
+							return p.columnid || p.toString();
+						}),
+					});
+				} else {
+					// Regular ROW_NUMBER without partition
+					query.rownums.push(col.as);
+				}
+			}
+			if (col.funcid && col.funcid.toUpperCase() === 'GROUP_ROW_NUMBER') {
+				query.grouprownums.push({as: col.as, columnIndex: 0}); // Track which column to use for grouping
 			}
 			//				console.log("colas:",colas);
 			// }

src/55functions.js

@@ -30,6 +30,12 @@ yy.FuncValue.prototype.toString = function () {
 		}
 		s += ')';
 	}
+
+	// Add OVER clause if present
+	if (this.over) {
+		s += ' ' + this.over.toString();
+	}
+
 	return s;
 };
 
@@ -249,6 +255,9 @@ stdlib.ROWNUM = function () {
 stdlib.ROW_NUMBER = function () {
 	return '1';
 };
+stdlib.GROUP_ROW_NUMBER = function () {
+	return '1';
+};
 
 stdlib.SQRT = function (s) {
 	return 'Math.sqrt(' + s + ')';

src/alasqlparser.jison

@@ -1377,21 +1377,21 @@ Aggregator
 	;
 
 FuncValue
-	: Literal LPAR (DISTINCT|ALL)? ExprList RPAR
+	: Literal LPAR (DISTINCT|ALL)? ExprList RPAR OverClause
 		{
 			var funcid = $1;
 			var exprlist = $4;
 			if(exprlist.length > 1 && (funcid.toUpperCase() == 'MIN' || funcid.toUpperCase() == 'MAX')) {
-					$$ = new yy.FuncValue({funcid: funcid, args: exprlist});
+					$$ = new yy.FuncValue({funcid: funcid, args: exprlist, over: $6});
 			} else if(alasql.aggr[$1]) {
 		    	$$ = new yy.AggrValue({aggregatorid: 'REDUCE',
-                      funcid: funcid, expression: exprlist.pop(),distinct:($3=='DISTINCT') });
+                      funcid: funcid, expression: exprlist.pop(),distinct:($3=='DISTINCT'), over: $6 });
 		    } else {
-			    $$ = new yy.FuncValue({funcid: funcid, args: exprlist});
+			    $$ = new yy.FuncValue({funcid: funcid, args: exprlist, over: $6});
 			};
 		}
-	| Literal LPAR RPAR
-		{ $$ = new yy.FuncValue({ funcid: $1 }) }
+	| Literal LPAR RPAR OverClause
+		{ $$ = new yy.FuncValue({ funcid: $1, over: $4 }) }
 	| IF LPAR ExprList RPAR
 		{ $$ = new yy.FuncValue({ funcid: 'IIF', args:$3 }) }
 	| REPLACE LPAR ExprList RPAR