These can include tables in relational databases, documents in document-based databases, key-value pairs in key-value stores, and nodes and edges in graph databases. Each structure is optimized for specific types of data access and querying.

The competition_rank table has the repeated string tell.

In the competition_results table, the columns first_place_bot, second_place_bot, and third_place_bot seem to express facts about a competition, but they also stand out as an independent concept that does not have a one-to-one relationship with a competition

Expressions aren't calculated a second or third time. They're calculated once and used where appropriate.

If a single quote is part of a string literal (Hell's Kitchen), escape it with a second single quote. The string literal 'Hell's Kitchen' causes an error because the single quote terminates the string and s Kitchen isn't SQL. The string 'Hell''s Kitchen' is valid and produces the desired result.

The home view may warn:

If I click "Purchase" and all 4 seats fail, it's not a big deal. I can always choose a different group of seats or choose a later showtime.

SQLite is a local database that's absolutely free and is supported in every major programming language. If you're ever tempted to use a file as data storage, use SQLite instead.

There are significant benefits to setting aside an entire logical layer that doesn't have to worry about messy inputs and outputs. In this course, we call it the domain laye

If we instantiate a concrete class inside a dependent, that dependent is tightly-coupled to a specific class. Tight coupling is bad. It limits our options.

exception. An exception is a run-time error. The compiler checks for syntax errors and verifies data type safety at compile-time, but it can never guarantee that our programs are correct at run-time

The video below demonstrates moving an existing class to a new package.

toString Returns a String representation of an object. By default, it returns the class name and a hexidecimal representation of the hashCode. That's not very useful, so it's common to override this method. hashCode Returns an int code that's used for storing an object in hashed data structures. getClass Returns the Class associated to the object. An instance of a Class contains meta-data (names, parameters, annotations) associated to a class. equals Returns a boolean that indicates if this instance is equal to another object. By default, it evaluates to true if the objects share the same memory location -- called reference equality -- they share the same reference. It's common to override this method to inspect individual values instead of comparing references.

Code changes:

repository is a complete history of file versions including additions, edits, and deletions