diff --git a/src/cli/user_command.rs b/src/cli/user_command.rs
index 7005fb9..b17ee20 100644
--- a/src/cli/user_command.rs
+++ b/src/cli/user_command.rs
@@ -137,14 +137,14 @@ async fn change_password_for_user(
 }
 
 async fn show_users(args: UserShowArgs, conn: &mut MySqlConnection) -> anyhow::Result<()> {
-    let user = crate::core::common::get_current_unix_user()?;
+    let unix_user = crate::core::common::get_current_unix_user()?;
 
     let users = if args.username.is_empty() {
-        crate::core::user_operations::get_all_database_users_for_user(&user, conn).await?
+        crate::core::user_operations::get_all_database_users_for_unix_user(&unix_user, conn).await?
     } else {
         let mut result = vec![];
         for username in args.username {
-            if let Err(e) = validate_ownership_of_user_name(&username, &user) {
+            if let Err(e) = validate_ownership_of_user_name(&username, &unix_user) {
                 eprintln!("{}", e);
                 eprintln!("Skipping...");
                 continue;
diff --git a/src/core/common.rs b/src/core/common.rs
index 6cf6974..2f7118d 100644
--- a/src/core/common.rs
+++ b/src/core/common.rs
@@ -42,6 +42,26 @@ pub fn get_unix_groups(user: &User) -> anyhow::Result<Vec<Group>> {
     Ok(groups)
 }
 
+/// This function creates a regex that matches items (users, databases)
+/// that belong to the user or any of the user's groups.
+pub fn create_user_group_matching_regex(user: &User) -> String {
+    let groups = get_unix_groups(user).unwrap_or_default();
+
+    if groups.is_empty() {
+        format!("{}(_.+)?", user.name)
+    } else {
+        format!(
+            "({}|{})(_.+)?",
+            user.name,
+            groups
+                .iter()
+                .map(|g| g.name.as_str())
+                .collect::<Vec<_>>()
+                .join("|")
+        )
+    }
+}
+
 pub fn validate_prefix_for_user<'a>(name: &'a str, user: &User) -> anyhow::Result<&'a str> {
     let user_groups = get_unix_groups(user)?;
 
diff --git a/src/core/database_operations.rs b/src/core/database_operations.rs
index 6b3ec11..9343988 100644
--- a/src/core/database_operations.rs
+++ b/src/core/database_operations.rs
@@ -8,7 +8,8 @@ use serde::{Deserialize, Serialize};
 use sqlx::{mysql::MySqlRow, prelude::*, MySqlConnection};
 
 use super::common::{
-    get_current_unix_user, get_unix_groups, quote_identifier, validate_prefix_for_user,
+    create_user_group_matching_regex, get_current_unix_user, quote_identifier,
+    validate_prefix_for_user,
 };
 
 pub async fn create_database(name: &str, conn: &mut MySqlConnection) -> anyhow::Result<()> {
@@ -56,10 +57,6 @@ struct DatabaseName {
 
 pub async fn get_database_list(conn: &mut MySqlConnection) -> anyhow::Result<Vec<String>> {
     let unix_user = get_current_unix_user()?;
-    let unix_groups = get_unix_groups(&unix_user)?
-        .into_iter()
-        .map(|g| g.name)
-        .collect::<Vec<_>>();
 
     let databases = sqlx::query_as::<_, DatabaseName>(
         r#"
@@ -69,11 +66,7 @@ pub async fn get_database_list(conn: &mut MySqlConnection) -> anyhow::Result<Vec
             AND `SCHEMA_NAME` REGEXP ?
         "#,
     )
-    .bind(format!(
-        "({}|{})_.+",
-        unix_user.name,
-        unix_groups.iter().map(|g| g.to_string()).join("|")
-    ))
+    .bind(create_user_group_matching_regex(&unix_user))
     .fetch_all(conn)
     .await
     .context(format!(
@@ -241,10 +234,6 @@ pub async fn get_all_database_privileges(
     conn: &mut MySqlConnection,
 ) -> anyhow::Result<Vec<DatabasePrivileges>> {
     let unix_user = get_current_unix_user()?;
-    let unix_groups = get_unix_groups(&unix_user)?
-        .into_iter()
-        .map(|g| g.name)
-        .collect::<Vec<_>>();
 
     let result = sqlx::query_as::<_, DatabasePrivileges>(&format!(
         indoc! {r#"
@@ -259,11 +248,7 @@ pub async fn get_all_database_privileges(
             .map(|field| format!("`{field}`"))
             .join(","),
     ))
-    .bind(format!(
-        "({}|{})_.+",
-        unix_user.name,
-        unix_groups.iter().map(|g| g.to_string()).join("|")
-    ))
+    .bind(create_user_group_matching_regex(&unix_user))
     .fetch_all(conn)
     .await
     .context("Failed to show databases")?;
diff --git a/src/core/user_operations.rs b/src/core/user_operations.rs
index 468ed85..0eefdad 100644
--- a/src/core/user_operations.rs
+++ b/src/core/user_operations.rs
@@ -6,7 +6,7 @@ use sqlx::{prelude::*, MySqlConnection};
 
 use crate::core::common::quote_literal;
 
-use super::common::{get_current_unix_user, get_unix_groups, validate_prefix_for_user};
+use super::common::{create_user_group_matching_regex, get_current_unix_user, validate_prefix_for_user};
 
 pub async fn create_database_user(db_user: &str, conn: &mut MySqlConnection) -> anyhow::Result<()> {
     let unix_user = get_current_unix_user()?;
@@ -71,22 +71,10 @@ pub struct DatabaseUser {
     pub authentication_string: String,
 }
 
-pub async fn get_all_database_users_for_user(
-    user: &User,
+pub async fn get_all_database_users_for_unix_user(
+    unix_user: &User,
     conn: &mut MySqlConnection,
 ) -> anyhow::Result<Vec<DatabaseUser>> {
-    let groups = get_unix_groups(user)?;
-
-    let regex = format!(
-        "({}|{})(_.+)?",
-        user.name,
-        groups
-            .iter()
-            .map(|g| g.name.as_str())
-            .collect::<Vec<_>>()
-            .join("|")
-    );
-
     let users = sqlx::query_as::<_, DatabaseUser>(
         r#"
           SELECT `User`, `Host`, `Password`, `authentication_string`
@@ -94,7 +82,7 @@ pub async fn get_all_database_users_for_user(
           WHERE `User` REGEXP ?
         "#,
     )
-    .bind(regex)
+    .bind(create_user_group_matching_regex(unix_user))
     .fetch_all(conn)
     .await?;