Issue type:
bug report

Database system/driver:
mysql / mariadb

TypeORM version:
0.2.5

example code:

import { In } from 'typeorm'
// ...
const res = await Entity.find({ where: { id: In([]) } })
// ER_PARSE_ERROR: You have an error in your SQL syntax; ...

Generated SQL is similar to

SELECT * FROM users WHERE id IN();

In MySql IN () (empty IN) is a syntax error. To fix it i propose that either:

• improve type annotations not to allow empty arrays to be inserted inside In method with guard for checking array.length to be > 0 (this would be closest to mysql spec)
• In method converts empty array to FALSE so the result would be similar to

SELECT * FROM users WHERE id IN(FALSE); -- FALSE seems to work if used also in NOT IN(FALSE)

• remove IN() clause (may or may not create other sql syntax errors)

SELECT * FROM users WHERE id;