Glossary

Glossary

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aggregation function

A function that combines multiple values to produce a single new value (e.g. sum, mean, median).

atomic

Describes a value not divisible into parts that one might want to work with separately. For example, if one wanted to work with first and last names separately, the values “Ada” and “Lovelace” would be atomic, but the value “Ada Lovelace” would not.

cascading delete

An SQL constraint requiring that if a given record is deleted, all records referencing it (via foreign key) in other tables must also be deleted.

case insensitive

Treating text as if upper and lower case characters were the same. See also: case sensitive.

case sensitive

Treating upper and lower case characters as different. See also: case insensitive.

comma-separated values (CSV)

A common textual representation for tables in which the values in each row are separated by commas.

cross product

A pairing of all elements of one set with all elements of another.

cursor

A pointer into a database that keeps track of outstanding operations.

database manager

A program that manages a database, such as SQLite.

fields

A set of data values of a particular type, one for each record in a table.

filter

To select only the records that meet certain conditions.

foreign key

One or more values in a database table that identify records in another table.

prepared statement

A template for an SQL query in which some values can be filled in.

primary key

One or more fields in a database table whose values are guaranteed to be unique for each record, i.e., whose values uniquely identify the entry.

query

A textual description of a database operation. Queries are expressed in a special-purpose language called SQL, and despite the name “query”, they may modify or delete data as well as interrogate it.

record

A set of related values making up a single entry in a database table, typically shown as a row. See also: fields.

referential integrity

The internal consistency of values in a database. If an entry in one table contains a foreign key, but the corresponding records don’t exist, referential integrity has been violated.

relational database

A collection of data organized into tables.

sentinel value

A value in a collection that has a special meaning, such as 999 to mean “age unknown”.

SQL

A special-purpose language for describing operations on relational databases.

SQL injection attack

An attack on a program in which the user’s input contains malicious SQL statements. If this text is copied directly into an SQL statement, it will be executed in the database.

table

A set of data in a relational database organized into a set of records, each having the same named fields.

wildcard

A character used in pattern matching. In SQL’s like operator, the wildcard “%” matches zero or more characters, so that %able% matches “fixable” and “tablets”.