[sql] SQL LIKE condition to check for integer?

I am using a set of SQL LIKE conditions to go through the alphabet and list all items beginning with the appropriate letter, e.g. to get all books where the title starts with the letter "A":

SELECT * FROM books WHERE title ILIKE "A%"

That's fine for letters, but how do I list all items starting with any number? For what it's worth this is on a Postgres DB.

If you want to search as string, you can cast to text like this:

SELECT * FROM books WHERE price::TEXT LIKE '123%'

Assuming that you're looking for "numbers that start with 7" rather than "strings that start with 7," maybe something like

select * from books where convert(char(32), book_id) like '7%'

Or whatever the Postgres equivalent of convert is.

Which one of those is indexable?

This one is definitely btree-indexable:

WHERE title >= '0' AND title < ':'

Note that ':' comes after '9' in ASCII.

Tested on PostgreSQL 9.5 :

-- only digits

select * from books where title ~ '^[0-9]*$';

or,

select * from books where title SIMILAR TO '[0-9]*';

-- start with digit

select * from books where title ~ '^[0-9]+';

I'm late to the party here, but if you're dealing with integers of a fixed length you can just do integer comparison:

SELECT * FROM books WHERE price > 89999 AND price < 90100;

In PostreSQL you can use SIMILAR TO operator (more):

-- only digits
select * from books where title similar to '^[0-9]*$';
-- start with digit
select * from books where title similar to '^[0-9]%$';

PostgreSQL supports regular expressions matching.

So, your example would look like

SELECT * FROM books WHERE title ~ '^\d+ ?' 

This will match a title starting with one or more digits and an optional space