WHERE

We learned how to get specific columns using SELECT. What if we're looking for specific rows? That is what the WHERE clause is for.

SELECT *
FROM daters
WHERE eye_color = 'brown';

Visually, it looks like this:

The expression of the WHERE clause tells us which rows we want. This expression has a special constraint. The WHERE expression must be a BOOL type, which is short for "boolean".

A boolean is 1 of 2 possible values: TRUE and FALSE (or 0 and 1 if you prefer numbers). A boolean can be created literally with the keywords TRUE and FALSE.

SELECT
  TRUE AS true_literal,
  FALSE AS false_literal;

They can also be created by comparing values using operators.

SELECT
  2 + 2 = 4 AS something_true,
  2 + 2 = 3 AS something_false;

Most of the time, these comparisons are used in a WHERE clause. The WHERE expression is evaluated per row, and if it outputs TRUE for a row, the row is kept in the result.

Let's try this out in a challenge!