Q: SQLite calculation on android

I am currently working on android application that can track income/outcome of a budget. In one of my database is named Transaction consist of:

• Amount
• Type (income/outcome)
• Date

since this is my first application I'm not really confident with my code, especially in the database. And now I'm making a trigger that can calculate percentage of outcome in a month. Can you check it,if my code is right or not, or not efficient. Here is tiny part of my Trigger code.

In my code I want to calculate percentage of total outcome from the first of a month until the current date .

"CREATE TRIGGER Calc"+
"AFTER INSERT"+
"ON" +transaction+
"FOR EACH ROW" +
"WHEN (SELET * FROM amount.transaction 
WHERE (strftime ('%d','now') - strftime('%d','start of month')) 
HAVING SUM(amount.transaction WHERE type.transaction IS "outcome") /SUM(amount.transaction WHERE type.transaction IS "income") * 0.01 )"

is it select * from amount.transaction needed? so the code can be much simpler?

0.01 there is 100%

sorry its so messed up since I'm just start in making android and I'm not really well with database. If you have any suggestion please tell me. Thanks before