diff --git a/internal/db/connection.go b/internal/db/connection.go
new file mode 100644
index 0000000..ae0f329
--- /dev/null
+++ b/internal/db/connection.go
@@ -0,0 +1,78 @@
+package db
+
+import (
+	"database/sql"
+	"fmt"
+	"log"
+
+	_ "github.com/lib/pq"
+)
+
+const (
+	host     = "202.46.28.160"
+	port     = 45432
+	user     = "5803024005"
+	password = "pw5803024005"
+	dbname   = "tgs01_5803024005"
+)
+
+var DB *sql.DB
+
+func InitDB() {
+	psqlconn := fmt.Sprintf("host=%s port=%d user=%s password=%s dbname=%s sslmode=disable", host, port, user, password, dbname)
+
+	var err error
+	DB, err = sql.Open("postgres", psqlconn)
+	if err != nil {
+		log.Fatal("Failed to open database connection:", err)
+	}
+
+	// Test the connection
+	err = DB.Ping()
+	if err != nil {
+		log.Fatal("Failed to ping database:", err)
+	}
+
+	log.Println("Database connection established successfully")
+
+	// Create tables if they don't exist
+	createTables()
+}
+
+func createTables() {
+	// Create Groups table
+	createGroupsTable := `
+	CREATE TABLE IF NOT EXISTS "Groups" (
+		"GroupID" SERIAL PRIMARY KEY,
+		"GroupName" VARCHAR(255) NOT NULL
+	);`
+
+	_, err := DB.Exec(createGroupsTable)
+	if err != nil {
+		log.Fatal("Failed to create Groups table:", err)
+	}
+
+	// Create Tasks table
+	createTasksTable := `
+	CREATE TABLE IF NOT EXISTS "Tasks" (
+		"TaskID" SERIAL PRIMARY KEY,
+		"TaskName" VARCHAR(255) NOT NULL,
+		"TaskDescription" TEXT,
+		"GroupID" INTEGER REFERENCES "Groups"("GroupID") ON DELETE CASCADE,
+		"IsDone" BOOLEAN DEFAULT FALSE,
+		"CreatedAt" TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+	);`
+
+	_, err = DB.Exec(createTasksTable)
+	if err != nil {
+		log.Fatal("Failed to create Tasks table:", err)
+	}
+
+	log.Println("Database tables created/verified successfully")
+}
+
+func CheckError(err error) {
+	if err != nil {
+		panic(err)
+	}
+}
diff --git a/internal/db/group_queries.go b/internal/db/group_queries.go
new file mode 100644
index 0000000..7da059c
--- /dev/null
+++ b/internal/db/group_queries.go
@@ -0,0 +1,100 @@
+package db
+
+import (
+	"database/sql"
+	"errors"
+)
+
+// GetAllGroups retrieves all groups from the database
+func GetAllGroups() ([]Group, error) {
+	var groups []Group
+	query := `SELECT "GroupID", "GroupName" FROM "Groups" ORDER BY "GroupID"`
+
+	rows, err := DB.Query(query)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var group Group
+		err := rows.Scan(&group.GroupID, &group.GroupName)
+		if err != nil {
+			return nil, err
+		}
+		groups = append(groups, group)
+	}
+
+	return groups, nil
+}
+
+// GetGroupByID retrieves a single group by ID
+func GetGroupByID(groupID int) (*Group, error) {
+	var group Group
+	query := `SELECT "GroupID", "GroupName" FROM "Groups" WHERE "GroupID" = $1`
+
+	err := DB.QueryRow(query, groupID).Scan(&group.GroupID, &group.GroupName)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, errors.New("group not found")
+		}
+		return nil, err
+	}
+
+	return &group, nil
+}
+
+// CreateGroup creates a new group in the database
+func CreateGroup(groupName string) (*Group, error) {
+	var group Group
+	query := `INSERT INTO "Groups" ("GroupName") VALUES ($1) RETURNING "GroupID", "GroupName"`
+
+	err := DB.QueryRow(query, groupName).Scan(&group.GroupID, &group.GroupName)
+	if err != nil {
+		return nil, err
+	}
+
+	return &group, nil
+}
+
+// UpdateGroup updates an existing group
+func UpdateGroup(groupID int, groupName string) error {
+	query := `UPDATE "Groups" SET "GroupName" = $1 WHERE "GroupID" = $2`
+
+	result, err := DB.Exec(query, groupName, groupID)
+	if err != nil {
+		return err
+	}
+
+	rowsAffected, err := result.RowsAffected()
+	if err != nil {
+		return err
+	}
+
+	if rowsAffected == 0 {
+		return errors.New("group not found")
+	}
+
+	return nil
+}
+
+// DeleteGroup deletes a group from the database
+func DeleteGroup(groupID int) error {
+	query := `DELETE FROM "Groups" WHERE "GroupID" = $1`
+
+	result, err := DB.Exec(query, groupID)
+	if err != nil {
+		return err
+	}
+
+	rowsAffected, err := result.RowsAffected()
+	if err != nil {
+		return err
+	}
+
+	if rowsAffected == 0 {
+		return errors.New("group not found")
+	}
+
+	return nil
+}
diff --git a/internal/db/models.go b/internal/db/models.go
new file mode 100644
index 0000000..c6f7a98
--- /dev/null
+++ b/internal/db/models.go
@@ -0,0 +1,19 @@
+package db
+
+import (
+	"time"
+)
+
+type Group struct {
+	GroupID   int    `json:"group_id"`
+	GroupName string `json:"group_name"`
+}
+
+type Task struct {
+	TaskID          int       `json:"task_id"`
+	TaskName        string    `json:"task_name"`
+	TaskDescription *string   `json:"task_description,omitempty"`
+	GroupID         int       `json:"group_id"`
+	IsDone          bool      `json:"is_done"`
+	CreatedAt       time.Time `json:"created_at"`
+}
diff --git a/internal/db/task_queries.go b/internal/db/task_queries.go
new file mode 100644
index 0000000..279daae
--- /dev/null
+++ b/internal/db/task_queries.go
@@ -0,0 +1,155 @@
+package db
+
+import (
+	"database/sql"
+	"errors"
+)
+
+// GetAllTasks retrieves all tasks from the database
+func GetAllTasks() ([]Task, error) {
+	var tasks []Task
+	query := `SELECT "TaskID", "TaskName", "TaskDescription", "GroupID", "IsDone", "CreatedAt" 
+			  FROM "Tasks" ORDER BY "CreatedAt" DESC`
+
+	rows, err := DB.Query(query)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var task Task
+		err := rows.Scan(&task.TaskID, &task.TaskName, &task.TaskDescription,
+			&task.GroupID, &task.IsDone, &task.CreatedAt)
+		if err != nil {
+			return nil, err
+		}
+		tasks = append(tasks, task)
+	}
+
+	return tasks, nil
+}
+
+// GetTasksByGroupID retrieves all tasks for a specific group
+func GetTasksByGroupID(groupID int) ([]Task, error) {
+	var tasks []Task
+	query := `SELECT "TaskID", "TaskName", "TaskDescription", "GroupID", "IsDone", "CreatedAt" 
+			  FROM "Tasks" WHERE "GroupID" = $1 ORDER BY "CreatedAt" DESC`
+
+	rows, err := DB.Query(query, groupID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var task Task
+		err := rows.Scan(&task.TaskID, &task.TaskName, &task.TaskDescription,
+			&task.GroupID, &task.IsDone, &task.CreatedAt)
+		if err != nil {
+			return nil, err
+		}
+		tasks = append(tasks, task)
+	}
+
+	return tasks, nil
+}
+
+// GetTaskByID retrieves a single task by ID
+func GetTaskByID(taskID int) (*Task, error) {
+	var task Task
+	query := `SELECT "TaskID", "TaskName", "TaskDescription", "GroupID", "IsDone", "CreatedAt" 
+			  FROM "Tasks" WHERE "TaskID" = $1`
+
+	err := DB.QueryRow(query, taskID).Scan(&task.TaskID, &task.TaskName,
+		&task.TaskDescription, &task.GroupID,
+		&task.IsDone, &task.CreatedAt)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, errors.New("task not found")
+		}
+		return nil, err
+	}
+
+	return &task, nil
+}
+
+// CreateTask creates a new task in the database
+func CreateTask(taskName string, taskDescription *string, groupID int) (*Task, error) {
+	var task Task
+	query := `INSERT INTO "Tasks" ("TaskName", "TaskDescription", "GroupID") 
+			  VALUES ($1, $2, $3) RETURNING "TaskID", "TaskName", "TaskDescription", "GroupID", "IsDone", "CreatedAt"`
+
+	err := DB.QueryRow(query, taskName, taskDescription, groupID).
+		Scan(&task.TaskID, &task.TaskName, &task.TaskDescription,
+			&task.GroupID, &task.IsDone, &task.CreatedAt)
+	if err != nil {
+		return nil, err
+	}
+
+	return &task, nil
+}
+
+// UpdateTask updates an existing task
+func UpdateTask(taskID int, taskName string, taskDescription *string) error {
+	query := `UPDATE "Tasks" SET "TaskName" = $1, "TaskDescription" = $2 
+			  WHERE "TaskID" = $3`
+
+	result, err := DB.Exec(query, taskName, taskDescription, taskID)
+	if err != nil {
+		return err
+	}
+
+	rowsAffected, err := result.RowsAffected()
+	if err != nil {
+		return err
+	}
+
+	if rowsAffected == 0 {
+		return errors.New("task not found")
+	}
+
+	return nil
+}
+
+// MarkTaskDone marks a task as completed
+func MarkTaskDone(taskID int) error {
+	query := `UPDATE "Tasks" SET "IsDone" = true WHERE "TaskID" = $1`
+
+	result, err := DB.Exec(query, taskID)
+	if err != nil {
+		return err
+	}
+
+	rowsAffected, err := result.RowsAffected()
+	if err != nil {
+		return err
+	}
+
+	if rowsAffected == 0 {
+		return errors.New("task not found")
+	}
+
+	return nil
+}
+
+// DeleteTask deletes a task from the database
+func DeleteTask(taskID int) error {
+	query := `DELETE FROM "Tasks" WHERE "TaskID" = $1`
+
+	result, err := DB.Exec(query, taskID)
+	if err != nil {
+		return err
+	}
+
+	rowsAffected, err := result.RowsAffected()
+	if err != nil {
+		return err
+	}
+
+	if rowsAffected == 0 {
+		return errors.New("task not found")
+	}
+
+	return nil
+}