add additional test

go.mod

@@ -18,4 +18,5 @@ require (
 	github.com/shopspring/decimal v1.3.1
 	github.com/stretchr/testify v1.7.0
 	github.com/volatiletech/null/v8 v8.1.2
+	gopkg.in/guregu/null.v4 v4.0.0
 )

go.sum

@@ -199,6 +199,8 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
+gopkg.in/guregu/null.v4 v4.0.0 h1:1Wm3S1WEA2I26Kq+6vcW+w0gcDo44YKYD7YIEJNHDjg=
+gopkg.in/guregu/null.v4 v4.0.0/go.mod h1:YoQhUrADuG3i9WqesrCmpNRwm1ypAgSHYqoOcTu/JrI=
 gopkg.in/inconshreveable/log15.v2 v2.0.0-20180818164646-67afb5ed74ec/go.mod h1:aPpfJ7XW+gOuirDoZ8gHhLh3kZ1B08FtV2bbmy7Jv3s=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=

tests/postgres/select_test.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/go-jet/jet/v2/qrm"
+	"gopkg.in/guregu/null.v4"
 
 	"github.com/stretchr/testify/require"
 
@@ -776,6 +777,98 @@ ORDER BY city.city_id, address.address_id, customer.customer_id;
 `)
 }
 
+// Test join with custom primary keys (null.Int)
+func TestExecutionCustomPKTypes2(t *testing.T) {
+
+	var dest []struct {
+		CityID   null.Int `sql:"primary_key" alias:"city.city_id"`
+		CityName string   `alias:"city.city"`
+
+		Customers []struct {
+			CustomerID null.Int `sql:"primary_key" alias:"customer_id"`
+			LastName   *string  `alias:"last_name"`
+
+			Address struct {
+				AddressID   null.Int `sql:"primary_key" alias:"AddressId"`
+				AddressLine string   `alias:"address.address"`
+			} `alias:"address.*"`
+		} `alias:"customer"`
+	}
+
+	stmt := City.
+		INNER_JOIN(Address, Address.CityID.EQ(City.CityID)).
+		INNER_JOIN(Customer, Customer.AddressID.EQ(Address.AddressID)).
+		SELECT(
+			City.CityID,
+			City.City,
+			Customer.CustomerID,
+			Customer.LastName,
+			Address.AddressID,
+			Address.Address,
+		).
+		WHERE(City.City.EQ(String("London")).OR(City.City.EQ(String("York")))).
+		ORDER_BY(City.CityID, Address.AddressID, Customer.CustomerID)
+
+	testutils.AssertDebugStatementSql(t, stmt, `
+SELECT city.city_id AS "city.city_id",
+     city.city AS "city.city",
+     customer.customer_id AS "customer.customer_id",
+     customer.last_name AS "customer.last_name",
+     address.address_id AS "address.address_id",
+     address.address AS "address.address"
+FROM dvds.city
+     INNER JOIN dvds.address ON (address.city_id = city.city_id)
+     INNER JOIN dvds.customer ON (customer.address_id = address.address_id)
+WHERE (city.city = 'London'::text) OR (city.city = 'York'::text)
+ORDER BY city.city_id, address.address_id, customer.customer_id;
+`, "London", "York")
+
+	err := stmt.Query(db, &dest)
+
+	require.NoError(t, err)
+	require.Equal(t, len(dest), 2)
+	testutils.AssertJSON(t, dest, `
+[
+	{
+		"CityID": 312,
+		"CityName": "London",
+		"Customers": [
+			{
+				"CustomerID": 252,
+				"LastName": "Hoffman",
+				"Address": {
+					"AddressID": 256,
+					"AddressLine": "1497 Yuzhou Drive"
+				}
+			},
+			{
+				"CustomerID": 512,
+				"LastName": "Vines",
+				"Address": {
+					"AddressID": 517,
+					"AddressLine": "548 Uruapan Street"
+				}
+			}
+		]
+	},
+	{
+		"CityID": 589,
+		"CityName": "York",
+		"Customers": [
+			{
+				"CustomerID": 497,
+				"LastName": "Sledge",
+				"Address": {
+					"AddressID": 502,
+					"AddressLine": "1515 Korla Way"
+				}
+			}
+		]
+	}
+]
+`)
+}
+
 func TestJoinQuerySliceWithPtrs(t *testing.T) {
 	type FilmsPerLanguage struct {
 		Language model.Language