Add const od Direction: NULL (#70)

builder_x.go

@@ -258,6 +258,7 @@ func (x *BuilderX) Build() *Built {
 		Aggs:       x.aggs,
 		Havings:    x.havings,
 		GroupBys:   x.groupBys,
+		Last:       x.last,
 		OrFromSql:  x.orFromSql,
 		Fxs:        x.sxs,
 		Svs:        x.svs,

sort.go

@@ -7,7 +7,7 @@
 // (the "License"); you may not use this file except in compliance with
 // the License.  You may obtain a copy of the License at
 //
-//     http://www.apache.org/licenses/LICENSE-2.0
+//	http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ -19,6 +19,7 @@ package sqlxb
 const (
 	asc  = "ASC"
 	desc = "DESC"
+	nul  = "NULL"
 )
 
 type Sort struct {
@@ -35,3 +36,7 @@ func ASC() string {
 func DESC() string {
 	return desc
 }
+
+func NULL() string {
+	return nul
+}

to_sql.go

@@ -29,10 +29,10 @@ type Built struct {
 	Havings    []Bb
 	GroupBys   []string
 	Aggs       []Bb
-
-	OrFromSql string
-	Fxs       []*FromX
-	Svs       []interface{}
+	Last       string
+	OrFromSql  string
+	Fxs        []*FromX
+	Svs        []interface{}
 
 	PageCondition *PageCondition
 }
@@ -244,6 +244,13 @@ func (built *Built) toPageSql(bp *strings.Builder) {
 	}
 }
 
+func (built *Built) toLastSql(bp *strings.Builder) {
+	if built.Last != "" {
+		bp.WriteString(SPACE)
+		bp.WriteString(built.Last)
+	}
+}
+
 func (built *Built) isOr(bb Bb) bool {
 	return bb.op == OR
 }
@@ -327,6 +334,7 @@ func (built *Built) sqlData(vs *[]interface{}, km map[string]string) (string, ma
 	built.toHavingSql(vs, &sb)
 	built.toSortSql(&sb)
 	built.toPageSql(&sb)
+	built.toLastSql(&sb)
 	dataSql := sb.String()
 	return dataSql, km
 }