Comparison Operators

Besides =, SQL has five more comparison operators:

<> and != mean the same. <> is the one from the SQL standard, which every database knows; != you may know from other programming languages. This course uses <>.

Watch the boundary. “Cheaper than $15” is price < 15, and the games that cost exactly $15 aren't in it:

SELECT title, price
FROM games
WHERE price < 15
ORDER BY price;

“$15 at most” is price <= 15, and the three games for $15 are in it too:

SELECT title, price
FROM games
WHERE price <= 15
ORDER BY price, title;

Either side of a comparison can also be a calculation. A customer has $50 and wants two copies of the same game, one for a friend. The games whose two copies cost $50 at most, the most expensive first:

SELECT title, price * 2 AS two_copies
FROM games
WHERE price * 2 <= 50
ORDER BY price DESC, title;

Typical mistake: the signs the other way round, => instead of >=. WHERE price => 40 ends with an error:

Error on line 1: near ">": syntax error

The equals sign always comes second, in the same order as you say it: “greater than or equal to”.