diff --git a/sql/custom_fields.sql b/sql/custom_fields.sql
index f965f15..ffc27b4 100644
--- a/sql/custom_fields.sql
+++ b/sql/custom_fields.sql
@@ -1,4 +1,6 @@
-create table custom_fields(
-    id INTEGER PRIMARY KEY,
-    name TEXT not null
+create table custom_fields
+(
+    id            integer primary key,
+    name          text not null,
+    custom_fields text not null
 );
\ No newline at end of file
diff --git a/sql/decks.sql b/sql/decks.sql
index 1842aad..3659ad1 100644
--- a/sql/decks.sql
+++ b/sql/decks.sql
@@ -1,9 +1,9 @@
 create table decks
 (
-    id       INTEGER
+    id       integer
         primary key autoincrement,
-    name     TEXT not null,
-    forward  TEXT not null,
-    backward TEXT not null,
-    filter   TEXT not null
+    name     text not null,
+    forward  text not null,
+    backward text not null,
+    filter   text not null
 );
\ No newline at end of file
diff --git a/sql/history.sql b/sql/history.sql
index 8fb9af8..80c5c5c 100644
--- a/sql/history.sql
+++ b/sql/history.sql
@@ -1,12 +1,12 @@
 create table history
 (
-    id INTEGER
+    id        integer
         primary key autoincrement,
-    deck_id INTEGER not null references decks on delete cascade,
-    word_id INTEGER not null references words on delete cascade,
-    timestamp INTEGER not null,
-    answer INTEGER not null,
-    before INTEGER not null,
-    after INTEGER not null,
-    fsrs INTEGER not null
+    deck_id   integer not null references decks on delete cascade,
+    word_id   integer not null references words on delete cascade,
+    timestamp integer not null,
+    answer    integer not null,
+    before    integer not null,
+    after     integer not null,
+    fsrs      integer not null
 );
diff --git a/sql/states.sql b/sql/states.sql
index da3d6f0..9c2da4f 100644
--- a/sql/states.sql
+++ b/sql/states.sql
@@ -1,16 +1,16 @@
 create table states
 (
-    id          INTEGER
+    id            integer
         primary key autoincrement,
-    word_id     INTEGER           not null
+    word_id       integer           not null
         references words
             on delete cascade,
-    deck_id      INTEGER              not null
+    deck_id       integer           not null
         references decks
             on delete cascade,
-    score       INTEGER default 1 not null,
-    last_opened INTEGER           not null,
-    fsrs_opened INTEGER not null,
-    fsrs_memory INTEGER not null,
-    fsrs_open_day INTEGER not null
+    score         integer default 1 not null,
+    last_opened   integer           not null,
+    fsrs_opened   integer           not null,
+    fsrs_memory   integer           not null,
+    fsrs_open_day integer           not null
 );
\ No newline at end of file
diff --git a/sql/word_groups.sql b/sql/word_groups.sql
index 8b10e51..b6f0f7d 100644
--- a/sql/word_groups.sql
+++ b/sql/word_groups.sql
@@ -1,6 +1,6 @@
 create table word_groups
 (
-    id   INTEGER
+    id   integer
         primary key autoincrement,
-    name TEXT not null
+    name text not null
 );
\ No newline at end of file
diff --git a/sql/words.sql b/sql/words.sql
index f883beb..440dd50 100644
--- a/sql/words.sql
+++ b/sql/words.sql
@@ -1,11 +1,11 @@
 create table words
 (
-    id       INTEGER
+    id       integer
         primary key autoincrement,
-    key      TEXT              not null,
-    value    TEXT              not null,
-    tags     TEXT              not null,
-    more     TEXT,
+    key      text              not null,
+    value    text              not null,
+    tags     text              not null,
+    more     text,
     group_id integer default 1 not null
         constraint words_word_groups_id_fk
             references word_groups
diff --git a/src/data/entities.rs b/src/data/entities.rs
index 60a2acc..28da05a 100644
--- a/src/data/entities.rs
+++ b/src/data/entities.rs
@@ -199,6 +199,7 @@ impl CardState {
 pub struct CustomField {
     pub id: Id,
     pub name: String,
+    pub identifier: String,
 }
 
 pub struct EntityHandle<E> {
diff --git a/src/data_provider/custom_fields.rs b/src/data_provider/custom_fields.rs
index feb81db..0b01770 100644
--- a/src/data_provider/custom_fields.rs
+++ b/src/data_provider/custom_fields.rs
@@ -1,41 +1,42 @@
-use crate::data::entities::{CustomField, WordGroup};
-use crate::data::repositories::DataRepository;
+use crate::data::entities::CustomField;
+use crate::data::repositories::{DataRepository, DataRepositoryInner};
 use crate::data_provider::{SqliteDbLayer, TableAccessQuerySet};
 use rusqlite::{Error, Params, Row};
 
-pub type CustomFieldRepository =
-    DataRepository<CustomField, SqliteDbLayer<CustomField, CustomFieldsQuerySet>>;
-
+pub type CustomFieldRepository = DataRepository<CustomField, CustomFieldDbLayer>;
+pub type CustomFieldRepositoryInner = DataRepositoryInner<CustomField, CustomFieldDbLayer>;
+pub type CustomFieldDbLayer = SqliteDbLayer<CustomField, CustomFieldsQuerySet>;
 pub struct CustomFieldsQuerySet;
-impl TableAccessQuerySet<WordGroup> for CustomFieldsQuerySet {
+impl TableAccessQuerySet<CustomField> for CustomFieldsQuerySet {
     fn load() -> &'static str {
-        "SELECT id, name FROM custom_fields"
+        "SELECT id, name, identifier FROM custom_fields"
     }
 
     fn save() -> &'static str {
-        "UPDATE custom_fields SET name = ?1 WHERE id = ?2"
+        "UPDATE custom_fields SET name = ?1, identifier = ?2 WHERE id = ?3"
     }
 
     fn add() -> &'static str {
-        "INSERT INTO word_groups (name) VALUES (?1)"
+        "INSERT INTO custom_fields (name, identifier) VALUES (?1, ?2)"
     }
 
     fn name() -> &'static str {
         "custom_fields"
     }
 
-    fn from_sql(row: &Row) -> Result<WordGroup, Error> {
-        Ok(WordGroup {
+    fn from_sql(row: &Row) -> Result<CustomField, Error> {
+        Ok(CustomField {
             id: row.get(0)?,
             name: row.get(1)?,
+            identifier: row.get(2)?,
         })
     }
 
-    fn insert_params(entity: &WordGroup) -> impl Params {
-        (&entity.name,)
+    fn insert_params(entity: &CustomField) -> impl Params {
+        (&entity.name, &entity.identifier)
     }
 
-    fn update_params(entity: &WordGroup) -> impl Params {
-        (&entity.name, entity.id)
+    fn update_params(entity: &CustomField) -> impl Params {
+        (&entity.name, &entity.identifier, entity.id)
     }
 }