Query

两种查询：

• select clause

• query predicates

Select Clauses

from /* ... variable declarations ... */
where /* ... logical formula ... */
select /* ... expressions ... */

类似SQL

from int x, int y
where x = 3 and y in [0 .. 2]
select x, y, x * y as product, "product: " + product as description
order by y desc

x	y	product	description
3	2	6	product: 6
3	1	3	product: 3
3	0	0	product: 0

Query Predicates

带有query标识的non-member predicate

query int getProduct(int x, int y) {
  x = 3 and
  y in [0 .. 2] and
  result = x * y
}

x	y	result
3	0	0
3	1	3
3	2	6

可以在其他位置调用查询谓词

class MultipleOfThree extends int {
  MultipleOfThree() { this = getProduct(_, _) }
}

from MultipleOfThree m
select m

查询子句select clause可以看作是匿名查询谓词，不能在其他地方调用