← Databases
Databases carry jargon that often hides the point: driver, index, transaction, replication. Below is what the terms mean in the context we use them — design, migration and reporting — and why they matter the moment data has to move from one platform to another.
Basic terms
- Driver (ODBC, JDBC)
- The piece in between that lets a program talk to a specific database. Without the right driver a reporting tool can do nothing, however open the database is.
- Index
- A lookup aid alongside the table. Makes queries fast, costs space and slows writing. A damaged index can usually be rebuilt.
- Transaction
- A sequence of steps that may only succeed or fail together. This is what stops an invoice being half posted.
- Schema
- The layout of the database: which tables, which fields, which relations. In a migration this is the first thing that has to be right.
In migration and reporting
- Data type
- The kind of value in a field: text, integer, amount, date. Most migration errors originate right here.
- Collation and character set
- The rules for sorting and characters. Differences here explain why accented names end up in the wrong place after a migration.
- Replication
- Keeping two databases automatically in step. Useful for reporting, but no substitute for a backup: a mistake is copied across neatly.
- Data warehouse
- A separate database where data from several systems comes together, arranged for querying rather than editing.
Most database discussions end up being about definitions rather than technology: who counts as a customer, when is an order complete. That question always returns.
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