diff --git a/database/main.js b/database/main.js
index 50a2b90..089ec87 100644
--- a/database/main.js
+++ b/database/main.js
@@ -1,7 +1,8 @@
 const pool = require('./postgresql.js');
 
 async function getDay(from_currency, conv_currency, date) {
-    if (!from_currency || !conv_currency || !date) return
+    if (!from_currency || !conv_currency) return new Error('fromCurrency and convCurrency are required');
+    else if (!date) return new Error('date is required')
 
     const data = await pool.query('SELECT from_currency, conv_currency, date, rate FROM currency ' +
         'WHERE from_currency = $1 AND conv_currency = $2 AND date = $3', [
@@ -10,26 +11,26 @@ async function getDay(from_currency, conv_currency, date) {
             date
         ]);
 
-    if (!data) return;
+    if (!data) return new Error('Missing data');
 
     return data['rows'][0];
 }
 
 async function getPeriod(from_currency, conv_currency, start_date, end_date) {
-    if (!from_currency || !conv_currency || !start_date || !end_date) return
+    if (!from_currency || !conv_currency) return new Error('from_currency and conv_currency are required');
+    else if(!start_date || !end_date) return new Error('start_date and end_date are required')
 
     const data = await pool.query('SELECT * FROM currency WHERE ' +
         '(date BETWEEN $3 AND $4) AND from_currency = $1 AND conv_currency = $2', [
-            from_currency,
-            conv_currency,
+            from_currency.toUpperCase(),
+            conv_currency.toUpperCase(),
             start_date,
             end_date
     ]);
 
-    if (!data) return;
+    if (!data) return new Error('Missing data');
 
     return data['rows'];
 }
 
-
-module.exports = { getDay, getPeriod };
+module.exports = { getDay, getPeriod };
\ No newline at end of file