diff --git a/core/database/database.go b/core/database/database.go
index dce4e46..87e0d68 100644
--- a/core/database/database.go
+++ b/core/database/database.go
@@ -33,18 +33,18 @@ func (db *Database) Connect(args []string) string {
 	defer db.lk.RUnlock()
 
 	if len(args) != 2 {
-		return "INVALID"
+		return INVALID
 	}
 
 	for _, u := range db.Config.Users {
 		if u.Name == args[0] {
 			if u.Password == args[1] {
-				return "DONE"
+				return DONE
 			}
 		}
 	}
 
-	return "INVALID"
+	return INVALID
 }
 
 func (db *Database) AddSet(args []string) string {
@@ -52,12 +52,12 @@ func (db *Database) AddSet(args []string) string {
 	defer db.lk.Unlock()
 
 	if len(args) != 1 {
-		return "INVALID"
+		return INVALID
 	}
 
 	db.Sets[args[0]] = make(Set) // args[0] is set name. see: TQL docs.
 
-	return "DONE"
+	return DONE
 }
 
 func (db *Database) AddSubSet(args []string) string {
@@ -65,17 +65,17 @@ func (db *Database) AddSubSet(args []string) string {
 	defer db.lk.Unlock()
 
 	if len(args) != 2 {
-		return "INVALID"
+		return INVALID
 	}
 
 	s, ok := db.Sets[args[0]] // set name args[0]
 	if !ok {
-		return "SNF"
+		return SET_NOT_FOUND
 	}
 
 	s[args[1]] = make(SubSet, 0) // subset name args[1]
 
-	return "DONE"
+	return DONE
 }
 
 func (db *Database) PushElement(args []string) string {
@@ -83,7 +83,7 @@ func (db *Database) PushElement(args []string) string {
 	defer db.lk.Unlock()
 
 	if len(args) != 4 {
-		return "INVALID"
+		return INVALID
 	}
 
 	setName := args[0]
@@ -93,12 +93,12 @@ func (db *Database) PushElement(args []string) string {
 
 	_, ok := db.Sets[setName][subSetName]
 	if !ok {
-		return "SSNF"
+		return SUB_SET_NOT_FOUND
 	}
 
 	timestamp, err := strconv.ParseInt(timeStr, 10, 64)
 	if err != nil {
-		return "INVALID"
+		return INVALID
 	}
 
 	t := time.Unix(timestamp, 0)
@@ -106,7 +106,7 @@ func (db *Database) PushElement(args []string) string {
 
 	db.Sets[setName][subSetName] = append(db.Sets[setName][subSetName], e)
 
-	return "DONE"
+	return DONE
 }
 
 func (db *Database) DropSet(args []string) string {
@@ -114,19 +114,19 @@ func (db *Database) DropSet(args []string) string {
 	defer db.lk.Unlock()
 
 	if len(args) != 1 {
-		return "INVALID"
+		return INVALID
 	}
 
 	setName := args[0]
 	_, ok := db.Sets[setName]
 
 	if !ok {
-		return "SNF"
+		return SET_NOT_FOUND
 	}
 
 	delete(db.Sets, setName)
 
-	return "DONE"
+	return DONE
 }
 
 func (db *Database) DropSubSet(args []string) string {
@@ -134,7 +134,7 @@ func (db *Database) DropSubSet(args []string) string {
 	defer db.lk.Unlock()
 
 	if len(args) != 2 {
-		return "INVALID"
+		return INVALID
 	}
 
 	setName := args[0]
@@ -142,12 +142,12 @@ func (db *Database) DropSubSet(args []string) string {
 
 	_, ok := db.Sets[setName][subSetName]
 	if !ok {
-		return "SSNF"
+		return SUB_SET_NOT_FOUND
 	}
 
 	delete(db.Sets[setName], subSetName)
 
-	return "DONE"
+	return DONE
 }
 
 func (db *Database) CleanSets(_ []string) string {
@@ -156,7 +156,7 @@ func (db *Database) CleanSets(_ []string) string {
 
 	db.Sets = make(Sets)
 
-	return "DONE"
+	return DONE
 }
 
 func (db *Database) CleanSet(args []string) string {
@@ -164,19 +164,19 @@ func (db *Database) CleanSet(args []string) string {
 	defer db.lk.Unlock()
 
 	if len(args) != 1 {
-		return "INVALID"
+		return INVALID
 	}
 
 	setName := args[0]
 
 	_, ok := db.Sets[setName]
 	if !ok {
-		return "SNF"
+		return SET_NOT_FOUND
 	}
 
 	db.Sets[setName] = make(Set)
 
-	return "DONE"
+	return DONE
 }
 
 func (db *Database) CleanSubSet(args []string) string {
@@ -184,7 +184,7 @@ func (db *Database) CleanSubSet(args []string) string {
 	defer db.lk.Unlock()
 
 	if len(args) != 2 {
-		return "INVALID"
+		return INVALID
 	}
 
 	setName := args[0]
@@ -192,12 +192,12 @@ func (db *Database) CleanSubSet(args []string) string {
 
 	_, ok := db.Sets[setName][subSetName]
 	if !ok {
-		return "SSNF"
+		return SUB_SET_NOT_FOUND
 	}
 
 	db.Sets[setName][subSetName] = make(SubSet, 0)
 
-	return "DONE"
+	return DONE
 }
 
 func (db *Database) CountSets(_ []string) string {
@@ -217,12 +217,12 @@ func (db *Database) CountSubSets(args []string) string {
 	defer db.lk.RUnlock()
 
 	if len(args) != 1 {
-		return "INVALID"
+		return INVALID
 	}
 
 	set, ok := db.Sets[args[0]]
 	if !ok {
-		return "SNF"
+		return SET_NOT_FOUND
 	}
 
 	i := 0
@@ -238,12 +238,12 @@ func (db *Database) CountElements(args []string) string {
 	defer db.lk.RUnlock()
 
 	if len(args) != 2 {
-		return "INVALID"
+		return INVALID
 	}
 
 	subSet, ok := db.Sets[args[0]][args[1]]
 	if !ok {
-		return "SSNF"
+		return SUB_SET_NOT_FOUND
 	}
 
 	i := 0
@@ -259,18 +259,18 @@ func (db *Database) GetElements(args []string) string {
 	defer db.lk.RUnlock()
 
 	if len(args) < 2 {
-		return "INVALID"
+		return INVALID
 	}
 
 	subSet, ok := db.Sets[args[0]][args[1]]
 	if !ok {
-		return "SSNF"
+		return SUB_SET_NOT_FOUND
 	}
 
 	if len(args) == 3 {
 		n, err := strconv.Atoi(args[2])
 		if err != nil || len(subSet) < n {
-			return "INVALID"
+			return INVALID
 		}
 
 		lastN := subSet[len(subSet)-n:]
diff --git a/core/database/database_test.go b/core/database/database_test.go
index ff8246c..503ae9a 100644
--- a/core/database/database_test.go
+++ b/core/database/database_test.go
@@ -18,7 +18,7 @@ func TestDataBase(t *testing.T) {
 		result := db.AddSet([]string{"testSet"})
 
 		assert.Equal(t, 1, len(db.SetsMap()))
-		assert.Equal(t, "DONE", result)
+		assert.Equal(t, DONE, result)
 	})
 
 	t.Run("AddSubSetTest", func(t *testing.T) {
@@ -26,11 +26,11 @@ func TestDataBase(t *testing.T) {
 		result := db.AddSubSet([]string{"testSet", "testSubSet"})
 
 		assert.Equal(t, 0, len(db.SetsMap()["testSet"]["testSubSet"]))
-		assert.Equal(t, "DONE", result)
+		assert.Equal(t, DONE, result)
 
 		result = db.AddSubSet([]string{"testInvalidSet", "testSubSet"})
 
-		assert.Equal(t, "SNF", result)
+		assert.Equal(t, SET_NOT_FOUND, result)
 	})
 
 	t.Run("pushElementTest", func(t *testing.T) {
@@ -40,7 +40,7 @@ func TestDataBase(t *testing.T) {
 		timeStr := fmt.Sprintf("%d", time.Now().Unix())
 		result := db.PushElement([]string{"testSet", "testSubSet", "testValue", timeStr})
 
-		assert.Equal(t, "DONE", result)
+		assert.Equal(t, DONE, result)
 		assert.Equal(t, 1, len(db.SetsMap()["testSet"]["testSubSet"]))
 		assert.Equal(t, "testValue", db.SetsMap()["testSet"]["testSubSet"][0].value)
 
@@ -49,7 +49,7 @@ func TestDataBase(t *testing.T) {
 
 		result = db.PushElement([]string{"invalidTestSet", "invalidTestSubSet", "testValue", timeStr})
 
-		assert.Equal(t, "SSNF", result)
+		assert.Equal(t, SUB_SET_NOT_FOUND, result)
 		assert.Equal(t, 1, len(db.SetsMap()["testSet"]["testSubSet"]))
 		assert.Equal(t, "testValue", db.SetsMap()["testSet"]["testSubSet"][0].value)
 
@@ -65,11 +65,11 @@ func TestDataBase(t *testing.T) {
 		result := db.DropSet([]string{"testSet"})
 
 		assert.Equal(t, 2, len(db.SetsMap()))
-		assert.Equal(t, "DONE", result)
+		assert.Equal(t, DONE, result)
 
 		result = db.DropSet([]string{"inavlidTestSet"})
 
-		assert.Equal(t, "SNF", result)
+		assert.Equal(t, SET_NOT_FOUND, result)
 		assert.Equal(t, 2, len(db.SetsMap()))
 	})
 
@@ -82,13 +82,13 @@ func TestDataBase(t *testing.T) {
 
 		result := db.DropSubSet([]string{"testSet", "subSetOne"})
 
-		assert.Equal(t, "DONE", result)
+		assert.Equal(t, DONE, result)
 		assert.Equal(t, 1, len(db.SetsMap()["testSet"]))
 		assert.Nil(t, db.SetsMap()["testSet"]["subSetOne"])
 
 		result = db.DropSubSet([]string{"secondTestSet", "subSetOne"})
 
-		assert.Equal(t, "SSNF", result)
+		assert.Equal(t, SUB_SET_NOT_FOUND, result)
 	})
 
 	t.Run("cleanTest", func(t *testing.T) {
@@ -111,24 +111,24 @@ func TestDataBase(t *testing.T) {
 
 		result := db.CleanSubSet([]string{"secondTestSet", "subSetTwo"})
 
-		assert.Equal(t, "DONE", result)
+		assert.Equal(t, DONE, result)
 		assert.Equal(t, 0, len(db.SetsMap()["secondTestSet"]["subSetTwo"]))
 
 		result = db.CleanSet([]string{"testSet"})
 
-		assert.Equal(t, "DONE", result)
+		assert.Equal(t, DONE, result)
 		assert.Equal(t, 0, len(db.SetsMap()["testSet"]))
 
 		result = db.CleanSets([]string{})
 
-		assert.Equal(t, "DONE", result)
+		assert.Equal(t, DONE, result)
 		assert.Equal(t, 0, len(db.SetsMap()))
 
 		result = db.CleanSet([]string{"invalidSet"})
-		assert.Equal(t, "SNF", result)
+		assert.Equal(t, SET_NOT_FOUND, result)
 
 		result = db.CleanSubSet([]string{"invalidSet", "invalidSubSet"})
-		assert.Equal(t, "SSNF", result)
+		assert.Equal(t, SUB_SET_NOT_FOUND, result)
 	})
 
 	t.Run("countTest", func(t *testing.T) {
@@ -176,8 +176,8 @@ func TestDataBase(t *testing.T) {
 		fmt.Print(trimmedResult)
 		resultsArray := strings.Split(trimmedResult, "  ")
 
-		assert.NotEqual(t, "INVALID", result)
-		assert.NotEqual(t, "SSNF", result)
+		assert.NotEqual(t, INVALID, result)
+		assert.NotEqual(t, SUB_SET_NOT_FOUND, result)
 		assert.Equal(t, 50, len(resultsArray))
 
 		result = db.GetElements([]string{"testSet", "subSetOne", "10"})
@@ -186,8 +186,8 @@ func TestDataBase(t *testing.T) {
 		trimmedResult, _ = strings.CutPrefix(trimmedResult, "  ")
 		resultsArray = strings.Split(trimmedResult, "  ")
 
-		assert.NotEqual(t, "INVALID", result)
-		assert.NotEqual(t, "SSNF", result)
+		assert.NotEqual(t, INVALID, result)
+		assert.NotEqual(t, SUB_SET_NOT_FOUND, result)
 		assert.Equal(t, 10, len(resultsArray))
 	})
 }
diff --git a/core/database/types.go b/core/database/types.go
index 80c2fbc..57e04e0 100644
--- a/core/database/types.go
+++ b/core/database/types.go
@@ -6,6 +6,14 @@ import (
 	"time"
 )
 
+const (
+	INVALID           = "INVALID"
+	DONE              = "DONE"
+	SET_NOT_FOUND     = "SNF"
+	SUB_SET_NOT_FOUND = "SSNF"
+	ELEMENT_NOT_FOUND = "ENF"
+)
+
 type Element struct {
 	value string    // currently ttrace only supports string datatype for value.
 	time  time.Time // will return and input from user as unix timestamp.