1. SQL – Dates and Times

2. How many columns should be returned for the following query?
SELECT *, students.*, name FROM students; 3 4 7
Syntax error
students
name
grade
enthusiasm
Josh
3.5
8.7

3. SELECT * and Qualified Names
SELECT * is shorthand for all the columns (in order) in the table.
* can be qualified (i.e. students.*) to make it unambiguous which table's columns are being included.

4. Problems with representations of time
Dates and Times are messy to represent.
Sometimes we only care about one or the other ("March 3rd" or 10:35PM)
Sometimes we want different precision (12: AM)
And don't even get started on time zones.
Many competing standards

5. ISO 8601 date: YYYY-MM-DD time: HH:MM:SS.SSS
datetime: YYYY-MM-DD HH:MM:SS.SSS
Big benefit: lexicographic sort is chronological sort!
You can store this format as text, and convert to a date object on export.

6. How to add timestamps to SQLite
CREATE TABLE birthdays (name TEXT, birthday TEXT);
INSERT INTO birthdays VALUES ('Josh', ' '),
('Tom', ' :31:56.7'),
('Dick', '12:31:56.7');
SELECT * FROM birthdays;
But without a common format you can't compare them

7. SQLite date and time functions
Input is of the form:
'YYYY-MM-DD'
'HH:MM:SS.SSS' (seconds are optional)
'YYYY-MM-DD HH:MM:SS.SSS'
'now'
You can modify the timestamp by adding / removing time:
'99 days'
'-2 hours'
Details here:

8. SQLite date and time functions
The functions date, time, and datetime will take an input, apply any modifiers and return the resulting string.
SELECT date('now');
SELECT time('12:53', '1 hours'); -- 13:53:00
SELECT datetime(' ', '-3 days');
:00:00

9. What should this return? SELECT date('12:34');
Error (no date specified)