Develop a Python script that uses the Twitter API to fetch tweets containing a specific hashtag and saves them into a SQLite database. The script should support command line arguments for the hashtag to search and the number of tweets to fetch. Store tweet text, username, and timestamp in the database.

To create a Python script that fetches tweets containing a specific hashtag and saves them into an SQLite database, you'll need to follow these steps:

1. Install the required libraries: Tweepy for accessing the Twitter API and sqlite3 for working with SQLite databases.
2. Set up your Twitter Developer account and obtain your API keys and access tokens.
3. Create a new SQLite database and define the table structure.
4. Use Tweepy to authenticate with the Twitter API and fetch tweets based on the given hashtag.
5. Save the fetched tweets into the SQLite database.

Here's a sample script that implements the above steps:

```python
import tweepy
import sqlite3
import sys

# Replace these values with your own API keys and access tokens
consumer_key = "your_consumer_key"
consumer_secret = "your_consumer_secret"
access_token = "your_access_token"
access_token_secret = "your_access_token_secret"

def create_database():
    conn = sqlite3.connect("tweets.db")
    cursor = conn.cursor()
    
    cursor.execute("""
        CREATE TABLE IF NOT EXISTS tweets (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            username TEXT,
            tweet_text TEXT,
            timestamp TEXT
        )
    """)
    
    conn.commit()
    return conn

def save_tweet(conn, username, tweet_text, timestamp):
    cursor = conn.cursor()
    cursor.execute("""
        INSERT INTO tweets (username, tweet_text, timestamp)
        VALUES (?, ?, ?)
    """, (username, tweet_text, timestamp))
    conn.commit()

def fetch_tweets(hashtag, count):
    auth = tweepy.OAuthHandler(consumer_key, consumer_secret)
    auth.set_access_token(access_token, access_token_secret)

    api = tweepy.API(auth)

    tweets = tweepy.Cursor(api.search_tweets, q=hashtag, lang="en", tweet_mode="extended").items(count)

    return tweets

def main():
    if len(sys.argv) != 3:
        print("Usage: python script.py hashtag count")
        sys.exit(1)

    hashtag = sys.argv[1]
    count = int(sys.argv[2])

    conn = create_database()

    for tweet in fetch_tweets(hashtag, count):
        username = tweet.user.screen_name
        tweet_text = tweet.full_text
        timestamp = tweet.created_at

        save_tweet(conn, username, tweet_text, timestamp)
        print(f"Saved tweet from {username} at {timestamp}")

if __name__ == "__main__":
    main()
```

To run the script, use the following command:

```bash
python script.py hashtag count
```

Replace `hashtag` with the desired hashtag (including the '#' symbol) and `count` with the number of tweets you want to fetch.

Before running the script, make sure to replace the placeholders for the API keys and access tokens with your own values. You can obtain these by creating a Twitter Developer account and setting up an app.

Please note that this is just a basic example, and there are many ways to improve it, such as error handling, pagination support, etc.