diff --git a/backendV2/schemeV2.mock_data.sql b/backendV2/schemeV2.mock_data.sql
index 2d09d0a..7201901 100644
--- a/backendV2/schemeV2.mock_data.sql
+++ b/backendV2/schemeV2.mock_data.sql
@@ -8,31 +8,31 @@ TRUNCATE TABLE items;
 TRUNCATE TABLE users;
 SET FOREIGN_KEY_CHECKS = 1;
 
--- Users (roles 1–6, plain-text passwords)
+-- Users (roles 1–6, plain-text passwords; is_admin is BOOL)
 INSERT INTO users (username, password, email, first_name, last_name, role, is_admin) VALUES
-('admin',  'adminpass', 'admin@example.com',  'System', 'Admin',   6, true),
-('alice',  'alice123',  'alice@example.com',  'Alice',  'Andersen',1, false),
-('bob',    'bob12345',  'bob@example.com',    'Bob',    'Berg',    2, false),
-('carol',  'carol123',  'carol@example.com',  'Carol',  'Christensen', 3, false),
-('dave',   'dave123',   'dave@example.com',   'Dave',   'Dahl',    4, false),
-('erin',   'erin123',   'erin@example.com',   'Erin',   'Enevoldsen', 5, false),
-('frank',  'frank123',  'frank@example.com',  'Frank',  'Fisher',  2, false),
-('grace',  'grace123',  'grace@example.com',  'Grace',  'Gundersen',1, false),
-('heidi',  'heidi123',  'heidi@example.com',  'Heidi',  'Hansen',  4, false),
-('tech',   'techpass',  'tech@example.com',   'Tech',   'User',    5, true);
+('admin',  'adminpass', 'admin@example.com',  'System', 'Admin',   6, TRUE),
+('alice',  'alice123',  'alice@example.com',  'Alice',  'Andersen',1, FALSE),
+('bob',    'bob12345',  'bob@example.com',    'Bob',    'Berg',    2, FALSE),
+('carol',  'carol123',  'carol@example.com',  'Carol',  'Christensen', 3, FALSE),
+('dave',   'dave123',   'dave@example.com',   'Dave',   'Dahl',    4, FALSE),
+('erin',   'erin123',   'erin@example.com',   'Erin',   'Enevoldsen', 5, FALSE),
+('frank',  'frank123',  'frank@example.com',  'Frank',  'Fisher',  2, FALSE),
+('grace',  'grace123',  'grace@example.com',  'Grace',  'Gundersen',1, FALSE),
+('heidi',  'heidi123',  'heidi@example.com',  'Heidi',  'Hansen',  4, FALSE),
+('tech',   'techpass',  'tech@example.com',   'Tech',   'User',    5, TRUE);
 
--- Items (safe_nr is two digits or NULL; currently_borrowing aligns with active loans)
+-- Items (safe_nr is two digits or NULL; matches CHECK and UNIQUE constraint)
 INSERT INTO items (item_name, can_borrow_role, in_safe, safe_nr, last_borrowed_person, currently_borrowing) VALUES
-('Laptop A',           2, false, NULL, 'grace',  'bob'),
-('Laptop B',           2, true,  '01', NULL,     NULL),
-('Camera Canon',       3, true,  '02', 'erin',   NULL),
-('Microphone Rode',    1, true,  '03', 'grace',  NULL),
-('Tripod Manfrotto',   1, true,  '04', 'frank',  NULL),
-('Oscilloscope Tek',   4, true,  '05', NULL,     NULL),
-('VR Headset',         3, false, NULL, 'heidi',  'carol'),
-('Keycard Programmer', 6, true,  '06', 'admin',  NULL);
+('Laptop A',           2, FALSE, NULL, 'grace',  'bob'),
+('Laptop B',           2, TRUE,  '01', NULL,     NULL),
+('Camera Canon',       3, TRUE,  '02', 'erin',   NULL),
+('Microphone Rode',    1, TRUE,  '03', 'grace',  NULL),
+('Tripod Manfrotto',   1, TRUE,  '04', 'frank',  NULL),
+('Oscilloscope Tek',   4, TRUE,  '05', NULL,     NULL),
+('VR Headset',         3, FALSE, NULL, 'heidi',  'carol'),
+('Keycard Programmer', 6, TRUE,  '06', 'admin',  NULL);
 
--- Loans (JSON arrays, 6-digit numeric loan_code)
+-- Loans (JSON strings, 6-digit numeric loan_code per CHECK)
 -- Assumes the items above have ids 1..8 in insert order
 INSERT INTO loans (
   username,
@@ -47,7 +47,7 @@ INSERT INTO loans (
   deleted,
   note
 ) VALUES
--- Active loan: bob has Laptop A
+-- Active loan: bob has Laptop A (item id 1, locker "01")
 ('bob',
   '["01"]',
   '123456',
@@ -57,10 +57,10 @@ INSERT INTO loans (
   NULL,
   '[1]',
   '["Laptop A"]',
-  false,
+  FALSE,
   'Active loan - Laptop A'
 ),
--- Returned loan: frank had Tripod Manfrotto
+-- Returned loan: frank had Tripod Manfrotto (item id 5, locker "04")
 ('frank',
   '["04"]',
   '234567',
@@ -70,10 +70,10 @@ INSERT INTO loans (
   '2025-10-05 15:30:00',
   '[5]',
   '["Tripod Manfrotto"]',
-  false,
+  FALSE,
   'Completed loan'
 ),
--- Future reservation: dave will take Oscilloscope Tek
+-- Future reservation: dave will take Oscilloscope Tek (item id 6, locker "05")
 ('dave',
   '["05"]',
   '345678',
@@ -83,10 +83,10 @@ INSERT INTO loans (
   NULL,
   '[6]',
   '["Oscilloscope Tek"]',
-  false,
+  FALSE,
   'Reserved'
 ),
--- Active loan: carol has VR Headset
+-- Active loan: carol has VR Headset (item id 7, locker "02")
 ('carol',
   '["02"]',
   '456789',
@@ -96,10 +96,10 @@ INSERT INTO loans (
   NULL,
   '[7]',
   '["VR Headset"]',
-  false,
+  FALSE,
   'Active loan - VR Headset'
 ),
--- Soft-deleted historic loan: grace had Microphone + Tripod
+-- Soft-deleted historic loan: grace had Microphone + Tripod (item ids 4,5; lockers "03","04")
 ('grace',
   '["03","04"]',
   '567890',
@@ -109,11 +109,11 @@ INSERT INTO loans (
   '2025-09-03 16:45:00',
   '[4,5]',
   '["Microphone Rode","Tripod Manfrotto"]',
-  true,
+  TRUE,
   'Canceled/soft-deleted record'
 );
 
--- API keys (8-digit numeric keys)
+-- API keys (8-digit numeric keys per CHECK)
 INSERT INTO apiKeys (api_key, entry_name, last_used_at) VALUES
 ('12345678', 'CI token',     '2025-11-15 08:00:00'),
 ('87654321', 'Local dev',    NULL),