diff --git a/server/src/tables_data/handlers/put_table_data.rs b/server/src/tables_data/handlers/put_table_data.rs
index 570b7be..2a68cfb 100644
--- a/server/src/tables_data/handlers/put_table_data.rs
+++ b/server/src/tables_data/handlers/put_table_data.rs
@@ -4,6 +4,7 @@ use sqlx::{PgPool, Arguments, Postgres};
 use sqlx::postgres::PgArguments;
 use chrono::{DateTime, Utc};
 use common::proto::multieko2::tables_data::{PutTableDataRequest, PutTableDataResponse};
+use std::collections::HashMap;
 
 pub async fn put_table_data(
     db_pool: &PgPool,
@@ -12,9 +13,27 @@ pub async fn put_table_data(
     let profile_name = request.profile_name;
     let table_name = request.table_name;
     let record_id = request.id;
-    let data = request.data;
+    
+    // Preprocess and validate data
+    let mut processed_data = HashMap::new();
+    let mut null_fields = Vec::new();
+    
+    for (key, value) in request.data {
+        let trimmed = value.trim().to_string();
+        
+        if key == "firma" && trimmed.is_empty() {
+            return Err(Status::invalid_argument("Firma cannot be empty"));
+        }
+        
+        // Store fields that should be set to NULL
+        if key != "firma" && trimmed.is_empty() {
+            null_fields.push(key);
+        } else {
+            processed_data.insert(key, trimmed);
+        }
+    }
 
-    // Lookup profile (same as POST)
+    // Lookup profile
     let profile = sqlx::query!(
         "SELECT id FROM profiles WHERE name = $1",
         profile_name
@@ -25,7 +44,7 @@ pub async fn put_table_data(
 
     let profile_id = profile.ok_or_else(|| Status::not_found("Profile not found"))?.id;
 
-    // Lookup table_definition (same as POST)
+    // Lookup table_definition
     let table_def = sqlx::query!(
         r#"SELECT id, columns FROM table_definitions
         WHERE profile_id = $1 AND table_name = $2"#,
@@ -38,7 +57,7 @@ pub async fn put_table_data(
 
     let table_def = table_def.ok_or_else(|| Status::not_found("Table not found"))?;
 
-    // Parse columns from JSON (same as POST)
+    // Parse columns from JSON
     let columns_json: Vec<String> = serde_json::from_value(table_def.columns.clone())
         .map_err(|e| Status::internal(format!("Column parsing error: {}", e)))?;
 
@@ -58,7 +77,7 @@ pub async fn put_table_data(
     let user_columns: Vec<&String> = columns.iter().map(|(name, _)| name).collect();
 
     // Validate input columns
-    for key in data.keys() {
+    for key in processed_data.keys() {
         if !system_columns.contains(&key.as_str()) && !user_columns.contains(&key) {
             return Err(Status::invalid_argument(format!("Invalid column: {}", key)));
         }
@@ -69,8 +88,8 @@ pub async fn put_table_data(
     let mut set_clauses = Vec::new();
     let mut param_idx = 1;
 
-    // Add data parameters
-    for (col, value) in &data {
+    // Add data parameters for non-empty fields
+    for (col, value) in &processed_data {
         let sql_type = if system_columns.contains(&col.as_str()) {
             match col.as_str() {
                 "firma" => "TEXT",
@@ -91,7 +110,7 @@ pub async fn put_table_data(
                     .and_then(|s| s.parse::<usize>().ok())
                 {
                     if value.len() > max_len {
-                        return Err(Status::invalid_argument(format!("Value too long for {}", col)));
+                        return Err(Status::internal(format!("Value too long for {}", col)));
                     }
                 }
                 params.add(value)
@@ -116,6 +135,20 @@ pub async fn put_table_data(
         param_idx += 1;
     }
 
+    // Add NULL clauses for empty fields
+    for field in null_fields {
+        // Make sure the field is valid
+        if !system_columns.contains(&field.as_str()) && !user_columns.contains(&&field) {
+            return Err(Status::invalid_argument(format!("Invalid column to set NULL: {}", field)));
+        }
+        set_clauses.push(format!("\"{}\" = NULL", field));
+    }
+
+    // Ensure we have at least one field to update
+    if set_clauses.is_empty() {
+        return Err(Status::invalid_argument("No valid fields to update"));
+    }
+
     // Add ID parameter at the end
     params.add(record_id)
         .map_err(|e| Status::internal(format!("Failed to add record_id parameter: {}", e)))?;
diff --git a/server/tests/tables_data/handlers/mod.rs b/server/tests/tables_data/handlers/mod.rs
index 4cbdd4b..d9f93f4 100644
--- a/server/tests/tables_data/handlers/mod.rs
+++ b/server/tests/tables_data/handlers/mod.rs
@@ -1,3 +1,4 @@
 // tests/tables_data/mod.rs
 pub mod post_table_data_test;
+pub mod put_table_data_test;
 
diff --git a/server/tests/tables_data/handlers/put_table_data_test.rs b/server/tests/tables_data/handlers/put_table_data_test.rs
new file mode 100644
index 0000000..9d93a19
--- /dev/null
+++ b/server/tests/tables_data/handlers/put_table_data_test.rs
@@ -0,0 +1,314 @@
+// tests/tables_data/handlers/put_table_data_test.rs
+use rstest::{fixture, rstest};
+use sqlx::PgPool;
+use std::collections::HashMap;
+use common::proto::multieko2::tables_data::{PutTableDataRequest, PutTableDataResponse};
+use server::tables_data::handlers::put_table_data;
+use crate::common::setup_test_db;
+use tonic;
+use chrono::Utc;
+
+// Fixtures
+#[fixture]
+async fn pool() -> PgPool {
+    setup_test_db().await
+}
+
+#[fixture]
+async fn closed_pool(#[future] pool: PgPool) -> PgPool {
+    let pool = pool.await;
+    pool.close().await;
+    pool
+}
+
+#[fixture]
+async fn existing_record(#[future] pool: PgPool) -> (PgPool, i64) {
+    let pool = pool.await;
+
+    // Create a test record in the database
+    let record = sqlx::query!(
+        r#"
+        INSERT INTO "2025_adresar" (
+            firma, kz, drc, ulica, psc, mesto, stat, banka, ucet,
+            skladm, ico, kontakt, telefon, skladu, fax, deleted
+        )
+        VALUES (
+            'Original Company', 'Original KZ', 'Original DRC', 'Original Street',
+            '12345', 'Original City', 'Original Country', 'Original Bank',
+            'Original Account', 'Original SkladM', 'Original ICO',
+            'Original Contact', '+421123456789', 'Original SkladU', 'Original Fax',
+            false
+        )
+        RETURNING id
+        "#
+    )
+    .fetch_one(&pool)
+    .await
+    .unwrap();
+
+    (pool, record.id)
+}
+
+#[fixture]
+fn valid_request_template() -> HashMap<String, String> {
+    let mut map = HashMap::new();
+    map.insert("firma".into(), "Updated Company".into());
+    map.insert("kz".into(), "Updated KZ".into());
+    map.insert("drc".into(), "Updated DRC".into());
+    map.insert("ulica".into(), "Updated Street".into());
+    map.insert("psc".into(), "67890".into());
+    map.insert("mesto".into(), "Updated City".into());
+    map.insert("stat".into(), "Updated Country".into());
+    map.insert("banka".into(), "Updated Bank".into());
+    map.insert("ucet".into(), "987654321".into());
+    map.insert("skladm".into(), "Updated SkladM".into());
+    map.insert("ico".into(), "87654321".into());
+    map.insert("kontakt".into(), "Jane Doe".into());
+    map.insert("telefon".into(), "+421987654321".into());
+    map.insert("skladu".into(), "Updated SkladU".into());
+    map.insert("fax".into(), "+421987654300".into());
+    map
+}
+
+// Helper to check database state
+async fn assert_response_matches(pool: &PgPool, id: i64, response: &PutTableDataResponse) {
+    let db_record = sqlx::query!(r#"SELECT * FROM "2025_adresar" WHERE id = $1"#, id)
+        .fetch_one(pool)
+        .await
+        .unwrap();
+
+    assert_eq!(db_record.firma, "Updated Company");
+    assert_eq!(db_record.kz.unwrap_or_default(), "Updated KZ");
+    assert_eq!(db_record.drc.unwrap_or_default(), "Updated DRC");
+    assert_eq!(db_record.ulica.unwrap_or_default(), "Updated Street");
+    assert_eq!(db_record.psc.unwrap_or_default(), "67890");
+    assert_eq!(db_record.mesto.unwrap_or_default(), "Updated City");
+    assert_eq!(db_record.stat.unwrap_or_default(), "Updated Country");
+    assert_eq!(db_record.banka.unwrap_or_default(), "Updated Bank");
+    assert_eq!(db_record.ucet.unwrap_or_default(), "987654321");
+    assert_eq!(db_record.skladm.unwrap_or_default(), "Updated SkladM");
+    assert_eq!(db_record.ico.unwrap_or_default(), "87654321");
+    assert_eq!(db_record.kontakt.unwrap_or_default(), "Jane Doe");
+    assert_eq!(db_record.telefon.unwrap_or_default(), "+421987654321");
+    assert_eq!(db_record.skladu.unwrap_or_default(), "Updated SkladU");
+    assert_eq!(db_record.fax.unwrap_or_default(), "+421987654300");
+    assert!(!db_record.deleted, "Record should not be deleted");
+}
+
+// Tests
+#[rstest]
+#[tokio::test]
+async fn test_update_table_data_success(
+    #[future] existing_record: (PgPool, i64),
+    valid_request_template: HashMap<String, String>,
+) {
+    let (pool, id) = existing_record.await;
+
+    let request = PutTableDataRequest {
+        profile_name: "default".into(),
+        table_name: "2025_adresar".into(),
+        id,
+        data: valid_request_template,
+    };
+
+    let response = put_table_data(&pool, request).await.unwrap();
+
+    assert!(response.success);
+    assert_eq!(response.message, "Data updated successfully");
+    assert_eq!(response.updated_id, id);
+    assert_response_matches(&pool, id, &response).await;
+}
+
+#[rstest]
+#[tokio::test]
+async fn test_update_table_data_whitespace_trimming(
+    #[future] existing_record: (PgPool, i64),
+    valid_request_template: HashMap<String, String>,
+) {
+    let (pool, id) = existing_record.await;
+
+    let mut data = valid_request_template;
+    data.insert("firma".into(), "  Updated Company  ".into());
+    data.insert("telefon".into(), "  +421987654321  ".into());
+
+    let request = PutTableDataRequest {
+        profile_name: "default".into(),
+        table_name: "2025_adresar".into(),
+        id,
+        data,
+    };
+
+    let response = put_table_data(&pool, request).await.unwrap();
+
+    // Verify trimmed values in response
+    assert_eq!(response.message, "Data updated successfully");
+
+    // Verify raw values in database
+    let db_record = sqlx::query!(r#"SELECT firma, telefon FROM "2025_adresar" WHERE id = $1"#, id)
+        .fetch_one(&pool)
+        .await
+        .unwrap();
+
+    assert_eq!(db_record.firma, "Updated Company"); // Trimmed
+    assert_eq!(db_record.telefon.unwrap(), "+421987654321"); // Trimmed
+}
+
+#[rstest]
+#[tokio::test]
+async fn test_update_table_data_empty_required_field(
+    #[future] existing_record: (PgPool, i64),
+    valid_request_template: HashMap<String, String>,
+) {
+    let (pool, id) = existing_record.await;
+
+    let mut data = valid_request_template;
+    data.insert("firma".into(), "".into());
+
+    let request = PutTableDataRequest {
+        profile_name: "default".into(),
+        table_name: "2025_adresar".into(),
+        id,
+        data,
+    };
+
+    let result = put_table_data(&pool, request).await;
+    assert!(result.is_err());
+    assert_eq!(result.unwrap_err().code(), tonic::Code::InvalidArgument);
+}
+
+#[rstest]
+#[tokio::test]
+async fn test_update_table_data_nonexistent_id(
+    #[future] pool: PgPool,
+    valid_request_template: HashMap<String, String>,
+) {
+    let pool = pool.await;
+
+    let request = PutTableDataRequest {
+        profile_name: "default".into(),
+        table_name: "2025_adresar".into(),
+        id: 9999, // Non-existent ID
+        data: valid_request_template,
+    };
+
+    let result = put_table_data(&pool, request).await;
+    assert!(result.is_err());
+    assert_eq!(result.unwrap_err().code(), tonic::Code::NotFound);
+}
+
+#[rstest]
+#[tokio::test]
+async fn test_update_table_data_deleted_record(
+    #[future] existing_record: (PgPool, i64),
+    valid_request_template: HashMap<String, String>,
+) {
+    let (pool, id) = existing_record.await;
+
+    // Mark the record as deleted
+    sqlx::query!(r#"UPDATE "2025_adresar" SET deleted = true WHERE id = $1"#, id)
+        .execute(&pool)
+        .await
+        .unwrap();
+
+    let request = PutTableDataRequest {
+        profile_name: "default".into(),
+        table_name: "2025_adresar".into(),
+        id,
+        data: valid_request_template,
+    };
+
+    let result = put_table_data(&pool, request).await;
+    assert!(result.is_err());
+    assert_eq!(result.unwrap_err().code(), tonic::Code::NotFound);
+}
+
+#[rstest]
+#[tokio::test]
+async fn test_update_table_data_clear_optional_fields(
+    #[future] existing_record: (PgPool, i64),
+    valid_request_template: HashMap<String, String>,
+) {
+    let (pool, id) = existing_record.await;
+
+    let mut data = valid_request_template;
+    data.insert("telefon".into(), String::new());
+    data.insert("ulica".into(), String::new());
+
+    let request = PutTableDataRequest {
+        profile_name: "default".into(),
+        table_name: "2025_adresar".into(),
+        id,
+        data,
+    };
+
+    let response = put_table_data(&pool, request).await.unwrap();
+
+    // Check database contains NULL for cleared fields
+    let db_record = sqlx::query!(r#"SELECT telefon, ulica FROM "2025_adresar" WHERE id = $1"#, id)
+        .fetch_one(&pool)
+        .await
+        .unwrap();
+
+    assert!(db_record.telefon.is_none());
+    assert!(db_record.ulica.is_none());
+}
+
+#[rstest]
+#[tokio::test]
+async fn test_update_table_data_max_length_fields(
+    #[future] existing_record: (PgPool, i64),
+    valid_request_template: HashMap<String, String>,
+) {
+    let (pool, id) = existing_record.await;
+
+    let mut data = valid_request_template;
+    data.insert("firma".into(), "a".repeat(255));
+    data.insert("telefon".into(), "1".repeat(20));
+
+    let request = PutTableDataRequest {
+        profile_name: "default".into(),
+        table_name: "2025_adresar".into(),
+        id,
+        data,
+    };
+
+    let _response = put_table_data(&pool, request).await.unwrap();
+
+    let db_record = sqlx::query!(r#"SELECT firma, telefon FROM "2025_adresar" WHERE id = $1"#, id)
+        .fetch_one(&pool)
+        .await
+        .unwrap();
+
+    assert_eq!(db_record.firma.len(), 255);
+    assert_eq!(db_record.telefon.unwrap().len(), 20);
+}
+
+#[rstest]
+#[tokio::test]
+async fn test_update_table_data_special_characters(
+    #[future] existing_record: (PgPool, i64),
+    valid_request_template: HashMap<String, String>,
+) {
+    let (pool, id) = existing_record.await;
+
+    let mut data = valid_request_template;
+    data.insert("ulica".into(), "Náměstí 28. října".into());
+    data.insert("telefon".into(), "+420 123-456.789".into());
+
+    let request = PutTableDataRequest {
+        profile_name: "default".into(),
+        table_name: "2025_adresar".into(),
+        id,
+        data,
+    };
+
+    let _response = put_table_data(&pool, request).await.unwrap();
+
+    let db_record = sqlx::query!(r#"SELECT ulica, telefon FROM "2025_adresar" WHERE id = $1"#, id)
+        .fetch_one(&pool)
+        .await
+        .unwrap();
+
+    assert_eq!(db_record.ulica.unwrap(), "Náměstí 28. října");
+    assert_eq!(db_record.telefon.unwrap(), "+420 123-456.789");
+}