Note the following syntax is for Postgres SQL, although they are all very similar

Before Starting to learn about SQL, know some of the essential characteristics of SQL language that’ll help your learning SQL journey:

SQL is not a case-sensitive language. We can write SQL keywords or identifiers in uppercase, lowercase, or mixed case. However, using uppercase letters for keywords is a standard coding convention.
SQL statements can be on one or more lines.
We can’t split SQL keywords across lines.
SQL keywords are not reserved; we can use them as identifiers for tables or columns.
SQL uses single-line comments that start with - and extend to the end of the line.
SQL also supports multiline comments that begin with /* and end with /.

MODULE 1: Basics

Select * FROM TABLE_Name
- Gets all rows and columns
Syntax: can’t have a comma after the last column name
- Capitalization does not matter for key words, column names, and table names in PostgreSQL

Rename Columns using keyword AS:

SELECT
  date AS DAY,
  open AS price
FROM
  tutorial.aapl_historical_stock_price

LIMIT keyword: limits the rows by the limit you decide at the end of your query

WHERE: Filters the data with the specified conditions

SELECT
  date AS DAY,
  open AS opening_price
FROM
  tutorial.aapl_historical_stock_price
WHERE open > 500
LIMIT 10

MODULE 2: Filtering

Comparison Operators (use in Where clause)

Equal: =
Not Equal: ! = or <>
Greater, and Greater than: > , > =
Less, and Less than: <, < =
Maths: +, -, *, /

Creating New Columns

You can create new columns by adding / subtracting two columns
You can also create constant columns

/* You can create new columns / constant columns */
SELECT date, high - low AS day_range, 999 as constant_column
FROM tutorial.aapl_historical_stock_price

Note that column values are put in SINGLE Quotes, where as column names should be put in DOUBLE quotes (if putting a space in col name)
```
SELECT
  *
FROM
  tutorial.city_populations
WHERE
  state > 'NY'
```
- String comparison is done by ASCII codes.
  - For example, state > ‘N’ → would give you NY, TX, .... etc.
    - This is because the second letter after N has a ASCII code of 0.
    - The values we got in results, such as NY, Y has a ASCII code > 0 so it is in the results.