support EXCEPT set operation

server/ast/union_clause.go

@@ -50,8 +50,11 @@ func nodeUnionClause(ctx *Context, node *tree.UnionClause) (*vitess.SetOp, error
 			unionType = vitess.IntersectStr
 		}
 	case tree.ExceptOp:
-		// This is not implemented on the GMS side, so we'll throw an appropriate error here
-		return nil, fmt.Errorf("EXCEPT is not yet supported")
+		if node.All {
+			unionType = vitess.ExceptAllStr
+		} else {
+			unionType = vitess.ExceptStr
+		}
 	default:
 		return nil, fmt.Errorf("unknown type of UNION operator: `%s`", node.Type.String())
 	}

testing/go/union_test.go

@@ -0,0 +1,128 @@
+// Copyright 2024 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (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
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package _go
+
+import (
+	"testing"
+
+	"github.com/dolthub/go-mysql-server/sql"
+)
+
+func TestUnion(t *testing.T) {
+	RunScripts(t, []ScriptTest{
+		{
+			Name: "union tests",
+			SetUpScript: []string{
+				`CREATE TABLE t1 (i INT PRIMARY KEY);`,
+				`CREATE TABLE t2 (j INT PRIMARY KEY);`,
+				`INSERT INTO t1 VALUES (1), (2), (3);`,
+				`INSERT INTO t2 VALUES (2), (3), (4);`,
+			},
+			Assertions: []ScriptTestAssertion{
+				{
+					Query: `SELECT * FROM t1 UNION SELECT * FROM t2;`,
+					Expected: []sql.Row{
+						{1},
+						{2},
+						{3},
+						{4},
+					},
+				},
+				{
+					Query: `SELECT 123 UNION SELECT 456;`,
+					Expected: []sql.Row{
+						{123},
+						{456},
+					},
+				},
+				{
+					Query: `SELECT * FROM (VALUES (123), (456)) a UNION SELECT * FROM (VALUES (456), (789)) b;`,
+					Expected: []sql.Row{
+						{123},
+						{456},
+						{789},
+					},
+				},
+			},
+		},
+	})
+}
+
+func TestIntersect(t *testing.T) {
+	RunScripts(t, []ScriptTest{
+		{
+			Name: "intersect tests",
+			SetUpScript: []string{
+				`CREATE TABLE t1 (i INT PRIMARY KEY);`,
+				`CREATE TABLE t2 (j INT PRIMARY KEY);`,
+				`INSERT INTO t1 VALUES (1), (2), (3);`,
+				`INSERT INTO t2 VALUES (2), (3), (4);`,
+			},
+			Assertions: []ScriptTestAssertion{
+				{
+					Query: `SELECT * FROM t1 INTERSECT SELECT * FROM t2;`,
+					Expected: []sql.Row{
+						{2},
+						{3},
+					},
+				},
+				{
+					Query:    `SELECT 123 INTERSECT SELECT 456;`,
+					Expected: []sql.Row{},
+				},
+				{
+					Query: `SELECT * FROM (VALUES (123), (456)) a INTERSECT SELECT * FROM (VALUES (456), (789)) b;`,
+					Expected: []sql.Row{
+						{456},
+					},
+				},
+			},
+		},
+	})
+}
+
+func TestExcept(t *testing.T) {
+	RunScripts(t, []ScriptTest{
+		{
+			Name: "except tests",
+			SetUpScript: []string{
+				`CREATE TABLE t1 (i INT PRIMARY KEY);`,
+				`CREATE TABLE t2 (j INT PRIMARY KEY);`,
+				`INSERT INTO t1 VALUES (1), (2), (3);`,
+				`INSERT INTO t2 VALUES (2), (3), (4);`,
+			},
+			Assertions: []ScriptTestAssertion{
+				{
+					Query: `SELECT * FROM t1 EXCEPT SELECT * FROM t2;`,
+					Expected: []sql.Row{
+						{1},
+					},
+				},
+				{
+					Query: `SELECT 123 EXCEPT SELECT 456;`,
+					Expected: []sql.Row{
+						{123},
+					},
+				},
+				{
+					Query: `SELECT * FROM (VALUES (123), (456)) a EXCEPT SELECT * FROM (VALUES (456), (789)) b;`,
+					Expected: []sql.Row{
+						{123},
+					},
+				},
+			},
+		},
+	})
+}