diff --git a/DEPS.bzl b/DEPS.bzl
index 39f1a4c0c9063..1ca6af86b095a 100644
--- a/DEPS.bzl
+++ b/DEPS.bzl
@@ -4904,14 +4904,16 @@ def go_deps():
         name = "com_sourcegraph_sourcegraph_appdash",
         build_file_proto_mode = "disable_global",
         importpath = "sourcegraph.com/sourcegraph/appdash",
-        sum = "h1:ucqkfpjg9WzSUubAO62csmucvxl4/JeW3F4I4909XkM=",
+        replace = "github.com/sourcegraph/appdash",
+        sum = "h1:IJ3DuWHPTJrsqtIqjfdmPTELdTFGefvrOa2eTeRBleQ=",
         version = "v0.0.0-20190731080439-ebfcffb1b5c0",
     )
     go_repository(
         name = "com_sourcegraph_sourcegraph_appdash_data",
         build_file_proto_mode = "disable_global",
         importpath = "sourcegraph.com/sourcegraph/appdash-data",
-        sum = "h1:e1sMhtVq9AfcEy8AXNb8eSg6gbzfdpYhoNqnPJa+GzI=",
+        replace = "github.com/sourcegraph/appdash-data",
+        sum = "h1:8ZnTA26bBOoPkAbbitKPgNlpw0Bwt7ZlpYgZWHWJR/w=",
         version = "v0.0.0-20151005221446-73f23eafcf67",
     )
     go_repository(
diff --git a/expression/builtin_convert_charset.go b/expression/builtin_convert_charset.go
index df9623dbe34ff..6d3b353c38ecc 100644
--- a/expression/builtin_convert_charset.go
+++ b/expression/builtin_convert_charset.go
@@ -322,7 +322,8 @@ func HandleBinaryLiteral(ctx sessionctx.Context, expr Expression, ec *ExprCollat
 				return expr
 			}
 			return BuildToBinaryFunction(ctx, expr)
-		} else if argChs == charset.CharsetBin && dstChs != charset.CharsetBin {
+		} else if argChs == charset.CharsetBin && dstChs != charset.CharsetBin &&
+			expr.GetType().GetType() != mysql.TypeNull {
 			ft := expr.GetType().Clone()
 			ft.SetCharset(ec.Charset)
 			ft.SetCollate(ec.Collation)
diff --git a/expression/integration_test.go b/expression/integration_test.go
index 31be5cf384c0d..826282516a25e 100644
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -7948,3 +7948,14 @@ func TestIfFunctionWithNull(t *testing.T) {
 	tk.MustQuery("select min(if(apply_to_now_days <= 30,loan,null)) as min, max(if(apply_to_now_days <= 720,loan,null)) as max from (select loan, datediff(from_unixtime(unix_timestamp('2023-05-18 18:43:43') + 18000), from_unixtime(apply_time/1000 + 18000)) as apply_to_now_days from orders) t1;").Sort().Check(
 		testkit.Rows("20000 35100"))
 }
+
+func TestIssue49526(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+
+	rows := tk.MustQuery("explain select null as a union all select 'a' as a;").Rows()
+	for _, r := range rows {
+		require.NotContains(t, r[4], "from_binary")
+	}
+	tk.MustQuery("select null as a union all select 'a' as a;").Sort().Check(testkit.Rows("<nil>", "a"))
+}
diff --git a/go.mod b/go.mod
index 03432e7c3cce8..c3caa749de93c 100644
--- a/go.mod
+++ b/go.mod
@@ -269,4 +269,9 @@ replace (
 	github.com/dgrijalva/jwt-go => github.com/form3tech-oss/jwt-go v3.2.6-0.20210809144907-32ab6a8243d7+incompatible
 	github.com/pingcap/tidb/parser => ./parser
 	go.opencensus.io => go.opencensus.io v0.23.1-0.20220331163232-052120675fac
+
+	// TODO: `sourcegraph.com/sourcegraph/appdash` has been archived, and the original host has been removed.
+	// Please remove these dependencies.
+	sourcegraph.com/sourcegraph/appdash => github.com/sourcegraph/appdash v0.0.0-20190731080439-ebfcffb1b5c0
+	sourcegraph.com/sourcegraph/appdash-data => github.com/sourcegraph/appdash-data v0.0.0-20151005221446-73f23eafcf67
 )
diff --git a/go.sum b/go.sum
index 2215cb7ca17b4..c2eacd21aa432 100644
--- a/go.sum
+++ b/go.sum
@@ -893,6 +893,10 @@ github.com/smartystreets/goconvey v1.6.4/go.mod h1:syvi0/a8iFYH4r/RixwvyeAJjdLS9
 github.com/soheilhy/cmux v0.1.4/go.mod h1:IM3LyeVVIOuxMH7sFAkER9+bJ4dT7Ms6E4xg4kGIyLM=
 github.com/soheilhy/cmux v0.1.5 h1:jjzc5WVemNEDTLwv9tlmemhC73tI08BNOIGwBOo10Js=
 github.com/soheilhy/cmux v0.1.5/go.mod h1:T7TcVDs9LWfQgPlPsdngu6I6QIoyIFZDDC6sNE1GqG0=
+github.com/sourcegraph/appdash v0.0.0-20190731080439-ebfcffb1b5c0 h1:IJ3DuWHPTJrsqtIqjfdmPTELdTFGefvrOa2eTeRBleQ=
+github.com/sourcegraph/appdash v0.0.0-20190731080439-ebfcffb1b5c0/go.mod h1:V952P4GGl1v/MMynLwxVdWEbSZJx+n0oOO3ljnez+WU=
+github.com/sourcegraph/appdash-data v0.0.0-20151005221446-73f23eafcf67 h1:8ZnTA26bBOoPkAbbitKPgNlpw0Bwt7ZlpYgZWHWJR/w=
+github.com/sourcegraph/appdash-data v0.0.0-20151005221446-73f23eafcf67/go.mod h1:tNZjgbYncKL5HxvDULAr/mWDmFz4B7H8yrXEDlnoIiw=
 github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 github.com/spaolacci/murmur3 v1.1.0 h1:7c1g84S4BPRrfL5Xrdp6fOJ206sU9y293DDHaoy0bLI=
 github.com/spaolacci/murmur3 v1.1.0/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
@@ -1588,8 +1592,4 @@ sigs.k8s.io/structured-merge-diff/v4 v4.2.1/go.mod h1:j/nl6xW8vLS49O8YvXW1ocPhZa
 sigs.k8s.io/yaml v1.1.0/go.mod h1:UJmg0vDUVViEyp3mgSv9WPwZCDxu4rQW1olrI1uml+o=
 sigs.k8s.io/yaml v1.2.0 h1:kr/MCeFWJWTwyaHoR9c8EjH9OumOmoF9YGiZd7lFm/Q=
 sigs.k8s.io/yaml v1.2.0/go.mod h1:yfXDCHCao9+ENCvLSE62v9VSji2MKu5jeNfTrofGhJc=
-sourcegraph.com/sourcegraph/appdash v0.0.0-20190731080439-ebfcffb1b5c0 h1:ucqkfpjg9WzSUubAO62csmucvxl4/JeW3F4I4909XkM=
-sourcegraph.com/sourcegraph/appdash v0.0.0-20190731080439-ebfcffb1b5c0/go.mod h1:hI742Nqp5OhwiqlzhgfbWU4mW4yO10fP+LoT9WOswdU=
-sourcegraph.com/sourcegraph/appdash-data v0.0.0-20151005221446-73f23eafcf67 h1:e1sMhtVq9AfcEy8AXNb8eSg6gbzfdpYhoNqnPJa+GzI=
-sourcegraph.com/sourcegraph/appdash-data v0.0.0-20151005221446-73f23eafcf67/go.mod h1:L5q+DGLGOQFpo1snNEkLOJT2d1YTW66rWNzatr3He1k=
 stathat.com/c/consistent v1.0.0 h1:ezyc51EGcRPJUxfHGSgJjWzJdj3NiMU9pNfLNGiXV0c=