diff --git a/pkg/sql/opt/exec/execbuilder/testdata/explain b/pkg/sql/opt/exec/execbuilder/testdata/explain
index 22c3964d350a..cbb616712c98 100644
--- a/pkg/sql/opt/exec/execbuilder/testdata/explain
+++ b/pkg/sql/opt/exec/execbuilder/testdata/explain
@@ -454,7 +454,7 @@ vectorized: true
 │ order: +grantee,+privilege_type
 │
 └── • filter
-    │ filter: (table_catalog, table_schema, table_name) IN (('test', 'public', 'foo'),)
+    │ filter: ((table_catalog = 'test') AND (table_schema = 'public')) AND (table_name = 'foo')
     │
     └── • virtual table
           table: table_privileges@primary
diff --git a/pkg/sql/opt/exec/execbuilder/testdata/scalar b/pkg/sql/opt/exec/execbuilder/testdata/scalar
index dcadf6730c50..f98bb91723eb 100644
--- a/pkg/sql/opt/exec/execbuilder/testdata/scalar
+++ b/pkg/sql/opt/exec/execbuilder/testdata/scalar
@@ -1201,7 +1201,7 @@ vectorized: true
 • filter
 │ columns: (c0)
 │ estimated row count: 333 (missing stats)
-│ filter: CASE WHEN c0 IN (c0,) THEN ARRAY[NULL] ELSE ARRAY[] END IS NULL
+│ filter: CASE WHEN (c0 IS DISTINCT FROM CAST(NULL AS DECIMAL)) OR CAST(NULL AS BOOL) THEN ARRAY[NULL] ELSE ARRAY[] END IS NULL
 │
 └── • scan
       columns: (c0)
diff --git a/pkg/sql/opt/exec/execbuilder/testdata/select_index b/pkg/sql/opt/exec/execbuilder/testdata/select_index
index b05bdd938251..f60976202e18 100644
--- a/pkg/sql/opt/exec/execbuilder/testdata/select_index
+++ b/pkg/sql/opt/exec/execbuilder/testdata/select_index
@@ -823,7 +823,7 @@ vectorized: true
 └── • filter
     │ columns: (k, a, b)
     │ estimated row count: 333 (missing stats)
-    │ filter: ((a IN (6,)) AND (a > 6)) OR (b >= 4)
+    │ filter: ((a = 6) AND (a > 6)) OR (b >= 4)
     │
     └── • scan
           columns: (k, a, b)
diff --git a/pkg/sql/opt/exec/execbuilder/testdata/virtual b/pkg/sql/opt/exec/execbuilder/testdata/virtual
index 10256c5834f4..c88e6e12aa3e 100644
--- a/pkg/sql/opt/exec/execbuilder/testdata/virtual
+++ b/pkg/sql/opt/exec/execbuilder/testdata/virtual
@@ -139,7 +139,7 @@ vectorized: true
         │ equality: (oid) = (connamespace)
         │
         ├── • filter
-        │   │ filter: nspname IN ('public',)
+        │   │ filter: nspname = 'public'
         │   │
         │   └── • virtual table
         │         table: pg_namespace@primary
diff --git a/pkg/sql/opt/memo/testdata/stats/scan b/pkg/sql/opt/memo/testdata/stats/scan
index be10bfbd7b9e..509ccab962bb 100644
--- a/pkg/sql/opt/memo/testdata/stats/scan
+++ b/pkg/sql/opt/memo/testdata/stats/scan
@@ -537,18 +537,20 @@ project
  │    ├── project
  │    │    ├── columns: col1:27(bool)
  │    │    ├── immutable
- │    │    ├── stats: [rows=333333.333, distinct(27)=333333.333, null(27)=0]
- │    │    ├── inner-join (cross)
+ │    │    ├── stats: [rows=10000, distinct(27)=10000, null(27)=0]
+ │    │    ├── inner-join (hash)
  │    │    │    ├── columns: tab0.e:5(varchar) tab0.f:6("char") tab0.h:8(varchar) tab0.j:10(float!null) tab1.e:17(varchar) tab1.f:18("char") tab1.j:22(float!null)
- │    │    │    ├── stats: [rows=333333.333, distinct(5,6,8,17,18)=333333.333, null(5,6,8,17,18)=3.33333333e-05]
+ │    │    │    ├── multiplicity: left-rows(one-or-more), right-rows(one-or-more)
+ │    │    │    ├── stats: [rows=10000, distinct(10)=100, null(10)=0, distinct(22)=100, null(22)=0, distinct(5,6,8,17,18)=10000, null(5,6,8,17,18)=1e-06]
+ │    │    │    ├── fd: (10)==(22), (22)==(10)
  │    │    │    ├── scan t37953 [as=tab0]
  │    │    │    │    ├── columns: tab0.e:5(varchar) tab0.f:6("char") tab0.h:8(varchar) tab0.j:10(float!null)
- │    │    │    │    └── stats: [rows=1000, distinct(5,6,8)=1000, null(5,6,8)=0.001]
+ │    │    │    │    └── stats: [rows=1000, distinct(10)=100, null(10)=0, distinct(5,6,8)=1000, null(5,6,8)=0.001]
  │    │    │    ├── scan t37953 [as=tab1]
  │    │    │    │    ├── columns: tab1.e:17(varchar) tab1.f:18("char") tab1.j:22(float!null)
- │    │    │    │    └── stats: [rows=1000, distinct(17,18)=1000, null(17,18)=0.1]
+ │    │    │    │    └── stats: [rows=1000, distinct(22)=100, null(22)=0, distinct(17,18)=1000, null(17,18)=0.1]
  │    │    │    └── filters
- │    │    │         └── tab0.j:10 IN (tab1.j:22,) [type=bool, outer=(10,22)]
+ │    │    │         └── tab0.j:10 = tab1.j:22 [type=bool, outer=(10,22), constraints=(/10: (/NULL - ]; /22: (/NULL - ]), fd=(10)==(22), (22)==(10)]
  │    │    └── projections
  │    │         └── CASE WHEN ilike_escape(regexp_replace(tab0.h:8, tab1.e:17, tab0.f:6, tab0.e:5::STRING), tab1.f:18, '') THEN true ELSE false END [as=col1:27, type=bool, outer=(5,6,8,17,18), immutable]
  │    └── filters
diff --git a/pkg/sql/opt/norm/rules/scalar.opt b/pkg/sql/opt/norm/rules/scalar.opt
index e72005f6e873..71b012b776fd 100644
--- a/pkg/sql/opt/norm/rules/scalar.opt
+++ b/pkg/sql/opt/norm/rules/scalar.opt
@@ -86,6 +86,16 @@ $input
 =>
 (Null (BoolType))
 
+[SimplifyInSingleElement, Normalize]
+(In $left:* (Tuple [ $right:* ]))
+=>
+(Eq $left $right)
+
+[SimplifyNotInSingleElement, Normalize]
+(NotIn $left:* (Tuple [ $right:* ]))
+=>
+(Ne $left $right)
+
 # UnifyComparisonTypes takes a mixed-type comparison between a non-constant and
 # a constant and, if appropriate, converts the constant to the type of the
 # non-constant to allow constraints to be generated.
diff --git a/pkg/sql/opt/norm/testdata/rules/assign_placeholders b/pkg/sql/opt/norm/testdata/rules/assign_placeholders
index 8d27ff305c64..fa57bef072f3 100644
--- a/pkg/sql/opt/norm/testdata/rules/assign_placeholders
+++ b/pkg/sql/opt/norm/testdata/rules/assign_placeholders
@@ -58,7 +58,8 @@ select
  │    ├── key: (1-3)
  │    └── fd: (1-3)-->(4)
  └── filters
-      └── (a:1, b:2) IN ((1, 2),) [outer=(1,2), constraints=(/1/2: [/1/2 - /1/2]; /2: [/2 - /2]; tight), fd=()-->(1,2)]
+      ├── a:1 = 1 [outer=(1), constraints=(/1: [/1 - /1]; tight), fd=()-->(1)]
+      └── b:2 = 2 [outer=(2), constraints=(/2: [/2 - /2]; tight), fd=()-->(2)]
 
 # The normalized expression above can be explored into a constrained scan.
 opt
diff --git a/pkg/sql/opt/norm/testdata/rules/scalar b/pkg/sql/opt/norm/testdata/rules/scalar
index 297087215077..bf95270fcc81 100644
--- a/pkg/sql/opt/norm/testdata/rules/scalar
+++ b/pkg/sql/opt/norm/testdata/rules/scalar
@@ -239,7 +239,7 @@ project
  ├── scan a
  │    └── columns: s:4
  └── projections
-      └── s:4 NOT IN ('foo',) [as=r:7, outer=(4)]
+      └── s:4 != 'foo' [as=r:7, outer=(4)]
 
 # Don't sort, since the list is not constant.
 norm expect-not=NormalizeInConst
@@ -275,6 +275,111 @@ values
  ├── fd: ()-->(1)
  └── (true IN (NULL, NULL, ('201.249.149.90/18' & '97a7:3650:3dd8:d4e9:35fe:6cfb:a714:1c17/61') << 'e22f:2067:2ed2:7b07:b167:206f:f17b:5b7d/82'),)
 
+# --------------------------------------------------
+# SimplifyInSingleElement
+# --------------------------------------------------
+norm expect=SimplifyInSingleElement
+SELECT * FROM a WHERE k IN (1)
+----
+select
+ ├── columns: k:1!null i:2 f:3 s:4 arr:5
+ ├── cardinality: [0 - 1]
+ ├── key: ()
+ ├── fd: ()-->(1-5)
+ ├── scan a
+ │    ├── columns: k:1!null i:2 f:3 s:4 arr:5
+ │    ├── key: (1)
+ │    └── fd: (1)-->(2-5)
+ └── filters
+      └── k:1 = 1 [outer=(1), constraints=(/1: [/1 - /1]; tight), fd=()-->(1)]
+
+norm expect=SimplifyInSingleElement
+SELECT 1 IN (k) FROM a
+----
+project
+ ├── columns: "?column?":7!null
+ ├── scan a
+ │    ├── columns: k:1!null
+ │    └── key: (1)
+ └── projections
+      └── k:1 = 1 [as="?column?":7, outer=(1)]
+
+norm expect=SimplifyInSingleElement
+SELECT k+1 IN (i*2) FROM a
+----
+project
+ ├── columns: "?column?":7
+ ├── immutable
+ ├── scan a
+ │    ├── columns: k:1!null i:2
+ │    ├── key: (1)
+ │    └── fd: (1)-->(2)
+ └── projections
+      └── (k:1 + 1) = (i:2 * 2) [as="?column?":7, outer=(1,2), immutable]
+
+norm expect-not=SimplifyInSingleElement
+SELECT k IN (1,2) FROM a
+----
+project
+ ├── columns: "?column?":7!null
+ ├── scan a
+ │    ├── columns: k:1!null
+ │    └── key: (1)
+ └── projections
+      └── k:1 IN (1, 2) [as="?column?":7, outer=(1)]
+
+# --------------------------------------------------
+# SimplifyNotInSingleElement
+# --------------------------------------------------
+norm expect=SimplifyNotInSingleElement
+SELECT * FROM a WHERE k NOT IN (1)
+----
+select
+ ├── columns: k:1!null i:2 f:3 s:4 arr:5
+ ├── key: (1)
+ ├── fd: (1)-->(2-5)
+ ├── scan a
+ │    ├── columns: k:1!null i:2 f:3 s:4 arr:5
+ │    ├── key: (1)
+ │    └── fd: (1)-->(2-5)
+ └── filters
+      └── k:1 != 1 [outer=(1), constraints=(/1: (/NULL - /0] [/2 - ]; tight)]
+
+norm expect=SimplifyNotInSingleElement
+SELECT 1 NOT IN (k) FROM a
+----
+project
+ ├── columns: "?column?":7!null
+ ├── scan a
+ │    ├── columns: k:1!null
+ │    └── key: (1)
+ └── projections
+      └── k:1 != 1 [as="?column?":7, outer=(1)]
+
+norm expect=SimplifyNotInSingleElement
+SELECT k+1 NOT IN (i*2) FROM a
+----
+project
+ ├── columns: "?column?":7
+ ├── immutable
+ ├── scan a
+ │    ├── columns: k:1!null i:2
+ │    ├── key: (1)
+ │    └── fd: (1)-->(2)
+ └── projections
+      └── (k:1 + 1) != (i:2 * 2) [as="?column?":7, outer=(1,2), immutable]
+
+norm expect-not=SimplifyNotInSingleElement
+SELECT k NOT IN (1,2) FROM a
+----
+project
+ ├── columns: "?column?":7!null
+ ├── scan a
+ │    ├── columns: k:1!null
+ │    └── key: (1)
+ └── projections
+      └── k:1 NOT IN (1, 2) [as="?column?":7, outer=(1)]
+
 # --------------------------------------------------
 # EliminateExistsZeroRows
 # --------------------------------------------------
diff --git a/pkg/sql/opt/partialidx/testdata/implicator/or-expr b/pkg/sql/opt/partialidx/testdata/implicator/or-expr
index c27595e8075f..028f3155f115 100644
--- a/pkg/sql/opt/partialidx/testdata/implicator/or-expr
+++ b/pkg/sql/opt/partialidx/testdata/implicator/or-expr
@@ -55,7 +55,7 @@ a IN (1)
 a = 1 OR a = 2
 ----
 true
-└── remaining filters: a IN (1,)
+└── remaining filters: a = 1
 
 predtest vars=(a int)
 a IN (1, 2, 3)
@@ -146,7 +146,7 @@ a IN (1) OR a IN (2)
 a = 1 OR a = 2
 ----
 true
-└── remaining filters: (a IN (1,)) OR (a IN (2,))
+└── remaining filters: none
 
 predtest vars=(a int, b int)
 a IN (1, 2)