lxd/db/schema/query.go
func selectSchemaVersions(tx *sql.Tx) ([]int, error) {
	statement := `
SELECT version FROM schema ORDER BY version
`
	return query.SelectIntegers(tx, statement)
}
func selectSchemaVersions(tx *sql.Tx) ([]int, error) {
	statement := `
SELECT version FROM schema ORDER BY version
`
	return query.SelectIntegers(tx, statement)
}
// Return all versions in the schema table, in increasing order.