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databases/transactions-why-a-money-transfer-must-save-both-changes-or-neither.md Transactions: why a money transfer must save both changes or neither Sending £50 between two accounts takes two changes to a database. If the power fails between them, the money vanishes. A transaction groups… 5 min read · 23 Oct security/sql-injection-how-a-quote-mark-in-a-login-form-can-rewrite-the-databas.md SQL injection: how a quote mark in a login form can rewrite the database's question A login form builds a database question out of the words you type. If it glues your text straight into the question, your text can rewrite… 5 min read · 21 Oct databases/sql-indexes-why-finding-one-row-among-200-000-takes-about-18-steps.md SQL indexes: why finding one row among 200,000 takes about 18 steps A database with 200,000 customers can answer "find this email" by reading every row, or by reading about 18 entries. The difference is an… 4 min read · 20 Oct databases/database-transactions-why-moving-money-is-all-or-nothing.md Database transactions: why moving money is all or nothing Paying someone is really two changes in a database: take money from one account, add it to another. If the power dies between them, money… 6 min read · 7 Oct databases/what-is-a-database-index-find-one-row-without-reading-them-all.md What is a database index? Find one row without reading them all Ask a database for one person among a million rows and it could read every row until it finds them. That is slow. An index is the… 5 min read · 4 Oct