New method: func (ColumnList) As(tableAlias string) ProjectionList

internal/jet/column_list.go

@@ -1,5 +1,7 @@
 package jet
 
+import "strings"
+
 // ColumnList is a helper type to support list of columns as single projection
 type ColumnList []ColumnExpression
 
@@ -39,6 +41,21 @@ func (cl ColumnList) Except(excludedColumns ...Column) ColumnList {
 	return ret
 }
 
+// As will create new projection list where each column is wrapped with a new table alias.
+// tableAlias should be in the form 'name' or 'name.*', or it can also be an empty string.
+// For instance: If projection list has a column 'Artist.Name', and tableAlias is 'Musician.*', returned projection list will
+// have a column wrapped in alias 'Musician.Name'. If tableAlias is empty string, it removes existing table alias ('Artist.Name' becomes 'Name').
+func (cl ColumnList) As(tableAlias string) ProjectionList {
+	if tableAlias > "" {
+		tableAlias = strings.TrimRight(tableAlias, ".*") + "."
+	}
+	ret := make(ProjectionList, 0, len(cl))
+	for _, c := range cl {
+		ret = append(ret, c.AS(tableAlias+c.Name()))
+	}
+	return ret
+}
+
 func (cl ColumnList) fromImpl(subQuery SelectTable) Projection {
 	newProjectionList := ProjectionList{}
 

internal/jet/projection.go

@@ -31,11 +31,15 @@ func (pl ProjectionList) serializeForProjection(statement StatementType, out *SQ
 }
 
 // As will create new projection list where each column is wrapped with a new table alias.
-// tableAlias should be in the form 'name' or 'name.*'.
+// tableAlias should be in the form 'name' or 'name.*', or it can be an empty string, which will remove existing table alias.
 // For instance: If projection list has a column 'Artist.Name', and tableAlias is 'Musician.*', returned projection list will
-// have a column wrapped in alias 'Musician.Name'.
+// have a column wrapped in alias 'Musician.Name'. If tableAlias is empty string, it removes existing table alias ('Artist.Name' becomes 'Name').
 func (pl ProjectionList) As(tableAlias string) ProjectionList {
-	tableAlias = strings.TrimRight(tableAlias, ".*")
+	tableAliasWithDot := ""
+	if tableAlias != "" {
+		tableAlias = strings.TrimRight(tableAlias, ".*")
+		tableAliasWithDot = tableAlias + "."
+	}
 
 	newProjectionList := ProjectionList{}
 
@@ -43,16 +47,14 @@ func (pl ProjectionList) As(tableAlias string) ProjectionList {
 		switch p := projection.(type) {
 		case ProjectionList:
 			newProjectionList = append(newProjectionList, p.As(tableAlias))
-		case ColumnExpression:
-			newProjectionList = append(newProjectionList, newAlias(p, tableAlias+"."+p.Name()))
 		case ColumnList:
-			for _, c := range p {
-				newProjectionList = append(newProjectionList, newAlias(c, tableAlias+"."+c.Name()))
-			}
+			newProjectionList = append(newProjectionList, p.As(tableAlias))
+		case ColumnExpression:
+			newProjectionList = append(newProjectionList, newAlias(p, tableAliasWithDot+p.Name()))
 		case *alias:
 			newAlias := *p
 			_, columnName := extractTableAndColumnName(newAlias.alias)
-			newAlias.alias = tableAlias + "." + columnName
+			newAlias.alias = tableAliasWithDot + columnName
 			newProjectionList = append(newProjectionList, &newAlias)
 		}
 	}

internal/jet/projection_test.go

@@ -27,6 +27,18 @@ AVG(table1.col_int) AS "new_alias.avg",
 table2.col3 AS "new_alias.col3",
 table2.col4 AS "new_alias.col4"`)
 
+	aliasedProjectionList = projectionList.As("")
+
+	assertProjectionSerialize(t, aliasedProjectionList,
+		`table1.col3 AS "col3",
+SUM(table1.col_int) AS "sum",
+SUM(table1.col_int) AS "sum",
+table1.col_bool AS "col_bool",
+AVG(table1.col_int) AS "avg",
+AVG(table1.col_int) AS "avg",
+table2.col3 AS "col3",
+table2.col4 AS "col4"`)
+
 	subQueryProjections := projectionList.fromImpl(NewSelectTable(nil, "subQuery"))
 
 	assertProjectionSerialize(t, subQueryProjections,