diff --git a/core/src/lib.rs b/core/src/lib.rs
index 43f01bc2..36637680 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -76,6 +76,26 @@ impl TypedValue {
     }
 }
 
+// Put this here rather than in `db` simply because it's widely needed.
+pub trait SQLValueType {
+    fn value_type_tag(&self) -> i32;
+}
+
+impl SQLValueType for ValueType {
+    fn value_type_tag(&self) -> i32 {
+        match *self {
+            ValueType::Ref =>      0,
+            ValueType::Boolean =>  1,
+            ValueType::Instant =>  4,
+            // SQLite distinguishes integral from decimal types, allowing long and double to share a tag.
+            ValueType::Long =>     5,
+            ValueType::Double =>   5,
+            ValueType::String =>  10,
+            ValueType::Keyword => 13,
+        }
+    }
+}
+
 #[test]
 fn test_typed_value() {
     assert!(TypedValue::Boolean(false).is_congruent_with(None));
diff --git a/db/src/db.rs b/db/src/db.rs
index ee59276f..37d457ce 100644
--- a/db/src/db.rs
+++ b/db/src/db.rs
@@ -331,25 +331,6 @@ pub fn ensure_current_version(conn: &mut rusqlite::Connection) -> Result<DB> {
     }
 }
 
-pub trait SQLValueType {
-    fn value_type_tag(&self) -> i32;
-}
-
-impl SQLValueType for ValueType {
-    fn value_type_tag(&self) -> i32 {
-        match *self {
-            ValueType::Ref =>      0,
-            ValueType::Boolean =>  1,
-            ValueType::Instant =>  4,
-            // SQLite distinguishes integral from decimal types, allowing long and double to share a tag.
-            ValueType::Long =>     5,
-            ValueType::Double =>   5,
-            ValueType::String =>  10,
-            ValueType::Keyword => 13,
-        }
-    }
-}
-
 pub trait TypedSQLValue {
     fn from_sql_value_pair(value: rusqlite::types::Value, value_type_tag: i32) -> Result<TypedValue>;
     fn to_sql_value_pair<'a>(&'a self) -> (ToSqlOutput<'a>, i32);
diff --git a/db/src/lib.rs b/db/src/lib.rs
index 287c1454..cde13ad9 100644
--- a/db/src/lib.rs
+++ b/db/src/lib.rs
@@ -41,7 +41,6 @@ mod values;
 mod tx;
 
 pub use db::{
-    SQLValueType,
     TypedSQLValue,
     new_connection,
 };
diff --git a/query-projector/src/lib.rs b/query-projector/src/lib.rs
index 364e5c2f..061bdff1 100644
--- a/query-projector/src/lib.rs
+++ b/query-projector/src/lib.rs
@@ -27,11 +27,11 @@ use rusqlite::{
 };
 
 use mentat_core::{
+    SQLValueType,
     TypedValue,
 };
 
 use mentat_db::{
-    SQLValueType,
     TypedSQLValue,
 };