Select distinct first character based on the string column

Question

In SQLite I have a table of contacts with one of the columns being last_name . How can I get unique set of first characters of all last names in the table? Something like ['a', 'b', 'd', 'f', 'w'] . It would help if query would be case insensitive. I'm using SQLite on Android. Thanks

Answer 1

这可能有效：

SELECT DISTINCT lower(substr(last_name,1,1)) AS last_initial FROM my_table;