Add check to see if links table already exists

backend/setup_db.py

@@ -12,15 +12,21 @@ links = [
 
 # SQLite setup
 cur = con.cursor()
-cur.execute('''CREATE TABLE links (
-  url text NOT NULL, 
-  name text NOT NULL, 
-  clicks int NOT NULL, 
-  active int NOT NULL, 
-  position int NOT NULL UNIQUE,
-  UNIQUE(url, name)
-  )''')
-cur.executemany("INSERT INTO links VALUES (?,?,?,?,?)", links)
-con.commit()
+
+# test if table already exists
+cur.execute("SELECT name FROM sqlite_master WHERE type='table' AND name='links'")
+if cur.fetchone():
+  print('Links table already exists.')
+else:
+  cur.execute('''CREATE TABLE links (
+    url text NOT NULL, 
+    name text NOT NULL, 
+    clicks int NOT NULL, 
+    active int NOT NULL, 
+    position int NOT NULL UNIQUE,
+    UNIQUE(url, name)
+    )''')
+  cur.executemany('INSERT INTO links VALUES (?,?,?,?,?)', links)
+  con.commit()
 
 con.close()