entc/integration: add examples for sub-queries + minor fixed for sele…

…ctor builder (#2509)

* dialect/sql: move FROM to inside switch

* dialect/sql: adds simple example of subquery usage

* dialect/sql: adds a more complex example with join

* Apply suggestions from code review

Co-authored-by: Ariel Mashraki <7413593+a8m@users.noreply.github.com>

* dialect/sql: fix missing type and change modify to where

Co-authored-by: Ariel Mashraki <7413593+a8m@users.noreply.github.com>

dialect/sql/builder.go

@@ -2657,19 +2657,21 @@ func (s *Selector) Query() (string, []interface{}) {
 	} else {
 		b.WriteString("*")
 	}
-	b.WriteString(" FROM ")
 	switch t := s.from.(type) {
 	case *SelectTable:
+		b.WriteString(" FROM ")
 		t.SetDialect(s.dialect)
 		b.WriteString(t.ref())
 	case *Selector:
+		b.WriteString(" FROM ")
 		t.SetDialect(s.dialect)
 		b.Nested(func(b *Builder) {
 			b.Join(t)
 		})
 		b.WriteString(" AS ")
 		b.Ident(t.as)
 	case *WithBuilder:
+		b.WriteString(" FROM ")
 		t.SetDialect(s.dialect)
 		b.Ident(t.Name())
 	}

dialect/sql/builder_test.go

@@ -1288,6 +1288,14 @@ func TestBuilder(t *testing.T) {
 			wantQuery: "WITH `groups` AS (SELECT * FROM `groups` WHERE `name` = ?) SELECT `age` FROM `groups`",
 			wantArgs:  []interface{}{"bar"},
 		},
+		{
+			input:     SelectExpr(Raw("1")),
+			wantQuery: "SELECT 1",
+		},
+		{
+			input:     Select("*").From(SelectExpr(Raw("1")).As("s")),
+			wantQuery: "SELECT * FROM (SELECT 1) AS `s`",
+		},
 		{
 			input: func() Querier {
 				builder := Dialect(dialect.Postgres)

entc/integration/integration_test.go

@@ -680,6 +680,31 @@ func Select(t *testing.T, client *ent.Client) {
 	require.Len(gs, 2)
 	require.Equal(hub.QueryUsers().CountX(ctx), gs[0].UsersCount)
 	require.Equal(lab.QueryUsers().CountX(ctx), gs[1].UsersCount)
+
+	// Select Subquery.
+	t.Log("select subquery")
+	i, err := client.User.
+		Query().
+		Modify(func(s *sql.Selector) {
+			subQuery := sql.SelectExpr(sql.Raw("1")).As("s")
+			s.Select("*").From(subQuery)
+		}).
+		Int(ctx)
+	require.NoError(err)
+	require.Equal(1, i)
+
+	// Select with join.
+	u = client.User.Create().SetName("crossworth").SetAge(28).SaveX(ctx)
+	id := client.User.
+		Query().
+		Where(func(s *sql.Selector) {
+			subQuery := sql.Select(user.FieldID).
+				From(sql.Table(user.Table)).
+				Where(sql.EQ(s.C(user.FieldName), "crossworth"))
+			s.Join(subQuery).On(s.C(user.FieldID), subQuery.C(user.FieldID))
+		}).
+		OnlyIDX(ctx)
+	require.Equal(u.ID, id)
 }
 
 func ExecQuery(t *testing.T, client *ent.Client) {