Question

我在尝试创建关系代数的地方有以下代码：最终的RelNode relNode = relBuilder.scan（index）.build（）;

我正在寻找一个示例代码，可以在上面的代码中创建SELECE和WHERE子句。

Answer 1

您读过the documentation吗？那里有几个例子。

final RelNode node = builder
  .scan("EMP")
  .aggregate(builder.groupKey("DEPTNO"),
      builder.count(false, "C"),
      builder.sum(false, "S", builder.field("SAL")))
  .filter(
      builder.call(SqlStdOperatorTable.GREATER_THAN,
          builder.field("C"),
          builder.literal(10)))
  .build();
System.out.println(RelOptUtil.toString(node));

等同于SQL

SELECT deptno, count(*) AS c, sum(sal) AS s
FROM emp
GROUP BY deptno
HAVING count(*) > 10

使用RelBuilder如何创建SELECT和WHEREclause？

1 个答案: