Extend set operator to accept sets as parameters.

sqlbuilder/select_statement.go

@@ -9,6 +9,7 @@ import (
 type selectStatement interface {
 	Statement
 	expression
+	hasRows()
 
 	DISTINCT() selectStatement
 	FROM(table readableTable) selectStatement
@@ -33,6 +34,7 @@ func SELECT(projection ...projection) selectStatement {
 // mysql's subquery performance is horrible.
 type selectStatementImpl struct {
 	expressionInterfaceImpl
+	isRowsType
 
 	table       readableTable
 	distinct    bool

sqlbuilder/set_statement.go

@@ -15,6 +15,7 @@ const (
 type setStatement interface {
 	Statement
 	expression
+	hasRows()
 
 	ORDER_BY(clauses ...orderByClause) setStatement
 	LIMIT(limit int64) setStatement
@@ -23,43 +24,44 @@ type setStatement interface {
 	AsTable(alias string) expressionTable
 }
 
-func UNION(selects ...selectStatement) setStatement {
+func UNION(selects ...rowsType) setStatement {
 	return newSetStatementImpl(union, false, selects...)
 }
 
-func UNION_ALL(selects ...selectStatement) setStatement {
+func UNION_ALL(selects ...rowsType) setStatement {
 	return newSetStatementImpl(union, true, selects...)
 }
 
-func INTERSECT(selects ...selectStatement) setStatement {
+func INTERSECT(selects ...rowsType) setStatement {
 	return newSetStatementImpl(intersect, false, selects...)
 }
 
-func INTERSECT_ALL(selects ...selectStatement) setStatement {
+func INTERSECT_ALL(selects ...rowsType) setStatement {
 	return newSetStatementImpl(intersect, true, selects...)
 }
 
-func EXCEPT(selects ...selectStatement) setStatement {
+func EXCEPT(selects ...rowsType) setStatement {
 	return newSetStatementImpl(except, false, selects...)
 }
 
-func EXCEPT_ALL(selects ...selectStatement) setStatement {
+func EXCEPT_ALL(selects ...rowsType) setStatement {
 	return newSetStatementImpl(except, true, selects...)
 }
 
 // Similar to selectStatementImpl, but less complete
 type setStatementImpl struct {
 	expressionInterfaceImpl
+	isRowsType
 
 	operator      string
-	selects       []selectStatement
+	selects       []rowsType
 	orderBy       []orderByClause
 	limit, offset int64
 	// True if results of the union should be deduped.
 	all bool
 }
 
-func newSetStatementImpl(operator string, all bool, selects ...selectStatement) setStatement {
+func newSetStatementImpl(operator string, all bool, selects ...rowsType) setStatement {
 	setStatement := &setStatementImpl{
 		operator: operator,
 		selects:  selects,

sqlbuilder/set_statement_test.go

@@ -126,3 +126,39 @@ OFFSET $2;
 `)
 	assert.Equal(t, len(args), 2)
 }
+
+func TestUnionInUnion(t *testing.T) {
+	expectedSql := `
+(
+     (
+          SELECT table2.col3 AS "table2.col3",
+               table2.col3 AS "table2.col3"
+          FROM db.table2
+     )
+     UNION
+     
+     (
+          (
+               SELECT table1.col1 AS "table1.col1"
+               FROM db.table1
+          )
+          UNION ALL
+          (
+               SELECT table2.col3 AS "table2.col3"
+               FROM db.table2
+          )
+     )
+);
+`
+	query := UNION(
+		SELECT(table2Col3, table2Col3).FROM(table2),
+		UNION_ALL(table1.SELECT(table1Col1), table2.SELECT(table2Col3)),
+	)
+
+	queryStr, args, err := query.Sql()
+
+	fmt.Println(queryStr)
+	assert.NilError(t, err)
+	assert.Equal(t, len(args), 0)
+	assert.Equal(t, queryStr, expectedSql)
+}

sqlbuilder/types.go

@@ -1,5 +1,14 @@
 package sqlbuilder
 
+type rowsType interface {
+	clause
+	hasRows()
+}
+
+type isRowsType struct{}
+
+func (i *isRowsType) hasRows() {}
+
 // A clause that can be used in orderBy by
 
 // A clause that is selectable.