Add sql sample

.gitignore

@@ -0,0 +1 @@
+*.db

sql.py

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+#!/usr/bin/env python3
+# SAMPLE SQL FILE
+# Will create a file in the current directory 'blockchain.db'
+
+import sqlite3 as lite
+
+create_table = """
+CREATE TABLE IF NOT EXISTS Blockchain (
+    ID              INTEGER PRIMARY KEY AUTOINCREMENT,
+    PubKey          TEXT,
+    Coins           INTEGER
+);
+"""
+
+def CreateDataBase():
+  con = lite.connect("blockchain.db")
+  c = con.cursor()
+  c.execute(create_table)
+  print("Table Blockchain created.")
+
+def DeleteDataBase():
+  con = lite.connect("blockchain.db")
+  with con:
+    c = con.cursor()
+    c.execute("DROP TABLE IF EXISTS Blockchain;")
+    print("Table Blockchain deleted.")
+
+def AddPubKey(key, coins):
+  con = lite.connect("blockchain.db")
+  with con:
+    c = con.cursor()
+    c.execute("INSERT INTO Blockchain (PubKey, Coins) VALUES (?, ?);", (key, coins))
+
+def PrintPubKeys():
+  con = lite.connect("blockchain.db")
+  with con:
+    c = con.cursor()
+    c.execute("SELECT * FROM Blockchain;")
+    row = c.fetchall()
+    print(str(row))
+
+def GetCoinsByKey(key):
+  con = lite.connect("blockchain.db")
+  with con:
+    c = con.cursor()
+    c.execute("SELECT * FROM Blockchain WHERE PubKey = '{k}';".format(k=key))
+    row = c.fetchall()
+    if not row:
+      return None
+    return row[0][2] # return the amount of coins
+
+CreateDataBase()
+AddPubKey("91298e9812eh81298he9h182e", 420)
+PrintPubKeys()
+print(GetCoinsByKey("91298e9812eh81298he9h182e")) # => 420
+print(GetCoinsByKey("invalid_key"))               # => None
+
+DeleteDataBase()