Add API: SortRand() (#71)

builder_x.go

@@ -226,11 +226,17 @@ func (x *BuilderX) X(k string, vs ...interface{}) *BuilderX {
 }
 
 func (x *BuilderX) Sort(orderBy string, direction Direction) *BuilderX {
-	if orderBy == "" || direction == nil {
+	if orderBy == "" {
 		return x
 	}
-	sort := Sort{orderBy: orderBy, direction: direction()}
-	x.sorts = append(x.sorts, sort)
+	if direction == nil {
+		sort := Sort{orderBy: orderBy, direction: ""}
+		x.sorts = append(x.sorts, sort)
+	} else {
+		sort := Sort{orderBy: orderBy, direction: direction()}
+		x.sorts = append(x.sorts, sort)
+	}
+
 	return x
 }
 

sort.go

@@ -19,7 +19,6 @@ package sqlxb
 const (
 	asc  = "ASC"
 	desc = "DESC"
-	nul  = "NULL"
 )
 
 type Sort struct {
@@ -36,7 +35,3 @@ func ASC() string {
 func DESC() string {
 	return desc
 }
-
-func NULL() string {
-	return nul
-}

to_sql.go

@@ -221,8 +221,10 @@ func (built *Built) toSortSql(bp *strings.Builder) {
 	for i := 0; i < length; i++ {
 		sort := built.Sorts[i]
 		bp.WriteString(sort.orderBy)
-		bp.WriteString(SPACE)
-		bp.WriteString(sort.direction)
+		if sort.direction != "" {
+			bp.WriteString(SPACE)
+			bp.WriteString(sort.direction)
+		}
 		if i < length-1 {
 			bp.WriteString(COMMA)
 		}