diff --git a/backend/selab_script.sql b/backend/selab_script.sql
index e1cda129..a944d666 100644
--- a/backend/selab_script.sql
+++ b/backend/selab_script.sql
@@ -1,16 +1,17 @@
 DROP TRIGGER IF EXISTS trg_check_submission_before_deadline ON submission;
 DROP FUNCTION IF EXISTS check_submission_before_deadline();
+DROP FUNCTION IF EXISTS check_team_size_before_joining();
 
 DROP TABLE IF EXISTS submission CASCADE;
 DROP TABLE IF EXISTS status CASCADE;
-DROP TABLE IF EXISTS project CASCADE;
+DROP TABLE IF EXISTS file CASCADE;
 DROP TABLE IF EXISTS student_group CASCADE;
 DROP TABLE IF EXISTS team CASCADE;
-DROP TABLE IF EXISTS student_subject CASCADE;
+DROP TABLE IF EXISTS project CASCADE;
 DROP TABLE IF EXISTS teacher_subject CASCADE;
+DROP TABLE IF EXISTS student_subject CASCADE;
 DROP TABLE IF EXISTS subject CASCADE;
 DROP TABLE IF EXISTS website_user CASCADE;
-DROP TABLE IF EXISTS file CASCADE;
 
 CREATE TABLE website_user (
     uid TEXT PRIMARY KEY,
@@ -46,7 +47,9 @@ CREATE TABLE project (
     name TEXT NOT NULL,
     subject_id BIGSERIAL NOT NULL,
     description TEXT,
-    FOREIGN KEY (subject_id) REFERENCES subject(id) ON DELETE SET NULL
+    max_team_size INT NOT NULL DEFAULT 4, -- Added column for maximum team size
+    FOREIGN KEY (subject_id) REFERENCES subject(id) ON DELETE SET NULL,
+    CONSTRAINT deadline_check CHECK (deadline >= CURRENT_DATE)
 );
 
 CREATE TABLE team (
@@ -94,10 +97,7 @@ CREATE TABLE file (
     FOREIGN KEY (project_id) REFERENCES project(id) ON DELETE SET NULL
 );
 
--- Constraints and checks
-ALTER TABLE project ADD CONSTRAINT deadline_check CHECK (deadline >= CURRENT_DATE);
-
--- Trigger to prevent submissions after the project deadline
+-- Function to check submission deadline
 CREATE OR REPLACE FUNCTION check_submission_before_deadline()
 RETURNS TRIGGER AS $$
 DECLARE
@@ -117,3 +117,26 @@ CREATE TRIGGER trg_check_submission_before_deadline
 BEFORE INSERT ON submission
 FOR EACH ROW
 EXECUTE FUNCTION check_submission_before_deadline();
+
+-- Function to check team size before adding a new member
+CREATE OR REPLACE FUNCTION check_team_size_before_joining()
+RETURNS TRIGGER AS $$
+DECLARE
+    current_team_size INT;
+    max_size INT;
+BEGIN
+    SELECT COUNT(*) INTO current_team_size FROM student_group WHERE team_id = NEW.team_id;
+    SELECT max_team_size INTO max_size FROM project JOIN team ON team.project_id = project.id WHERE team.id = NEW.team_id;
+
+    IF current_team_size >= max_size THEN
+        RAISE EXCEPTION 'The team is already at its maximum capacity of % members.', max_size;
+    END IF;
+
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE TRIGGER trg_check_team_size_before_joining
+BEFORE INSERT ON student_group
+FOR EACH ROW
+EXECUTE FUNCTION check_team_size_before_joining();