The IN keyword

When we need to find rows where a column matches any one of several possible values, we can write it using multiple OR conditions. For example the following query is very long:

SELECT *
FROM table1
WHERE col1 = 'a' OR col1 = 'b' OR col1 = 'c' OR col1 = 'd' OR ...

We can simplify it by using the IN keyword like this:

SELECT *
FROM table1
WHERE col1 IN ('a', 'b', 'c', 'd', 'e', 'f')

This shorter version does exactly the same thing: it returns rows where col1 equals any of the values listed in the parentheses.