Elias Week 4 database #54
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…nstead of nested callbacks. This makes the code easier to read and maintain. I added a foreign key constraint for the invited_by field in the Invitee table. This ensures that each person invited actually exists in the table, improving data integrity. I updated how we manage the database connection to use promises, which makes it easier to handle errors that may occur. I also improved the comments in the code to make it clearer how we set up the database and create the tables.
| const database = client.db('dataBaseWeek4'); | ||
| const accounts = database.collection('accounts'); |
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suggestion: these two strings are used across files. Better to make them constants.
| const database = client.db('dataBaseWeek4'); | ||
| const accounts = database.collection('accounts'); |
| // Find the sender account | ||
| const senderAccount = await accounts.findOne({ account_number: fromAccountNumber }); | ||
| if (!senderAccount || senderAccount.balance < amount) { | ||
| throw new Error('Insufficient funds'); | ||
| } | ||
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| // Find the receiver account | ||
| const receiverAccount = await accounts.findOne({ account_number: toAccountNumber }); | ||
| if (!receiverAccount) { | ||
| throw new Error('Receiver account not found'); | ||
| } |
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Early returns or throws are always encouraged!
| $inc: { balance: -amount }, | ||
| $push: { | ||
| account_changes: { | ||
| change_number: senderAccount.account_changes.length + 1, |
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suggestion: using fromAccount.account_changes.length + 1 to know the next change_number is OK.
However, in real life one account may have a lot more change records. We don't really care what those changes are, we just want to know the maximum change number. Fetching all changes with the account can be expensive (since you need to transfer more bytes in the network. When you download something big from Internet, it is always slower than dowloading smaller files), and we try to only fetch the columns we need.
One solution is to have a function to get only the maximum change number (you have learned MAX sql syntax), and when you fetch the account data you don't fetch the changes column.
| try { | ||
| await client.connect(); | ||
| const db = client.db(dbName); | ||
| const collection = db.collection('populationData'); |
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suggestion: why not make populationData constant too?
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