Question

谁能告诉我到底SQL的WITH CUBE，和WITH ROLLUP实现什么样的效果，区别是什么，要是能举例说明，感激不尽

帮忙解决下，谢谢大家

Answer 1

The ROLLUP operator is useful in generating reports that contain subtotals and totals. The ROLLUP operator generates a result set that is similar to the result sets generated by the CUBE operator. For more information, see Summarizing Data Using CUBE.

The differences between CUBE and ROLLUP are:

CUBE generates a result set showing aggregates for all combinations of values in the selected columns.

ROLLUP generates a result set showing aggregates for a hierarchy of values in the selected columns.
For example, a simple table Inventory contains:

Item Color Quantity
-------------------- -------------------- --------------------------
Table Blue 124
Table Red 223
Chair Blue 101
Chair Red 210

This query generates a subtotal report:

SELECT CASE WHEN (GROUPING(Item) = 1) THEN 'ALL'
ELSE ISNULL(Item, 'UNKNOWN')
END AS Item,
CASE WHEN (GROUPING(Color) = 1) THEN 'ALL'
ELSE ISNULL(Color, 'UNKNOWN')
END AS Color,
SUM(Quantity) AS QtySum
FROM Inventory
GROUP BY Item, Color WITH ROLLUP

Item Color QtySum
-------------------- -------------------- --------------------------
Chair Blue 101.00
Chair Red 210.00
Chair ALL 311.00
Table Blue 124.00
Table Red 223.00
Table ALL 347.00
ALL ALL 658.00

(7 row(s) affected)

If the ROLLUP keyword in the query is changed to CUBE, the CUBE result set is the same, except these two additional rows are returned at the end:

ALL Blue 225.00
ALL Red 433.00

The CUBE operation generated rows for possible combinations of values from both Item and Color. For example, not only does CUBE report all possible combinations of Color values combined with the Item value Chair (Red, Blue, and Red + Blue), it also reports all possible combinations of Item values combined with the Color value Red (Chair, Table, and Chair + Table).

For each value in the columns on the right in the GROUP BY clause, the ROLLUP operation does not report all possible combinations of values from the column (or columns) on the left. For example, ROLLUP does not report all the possible combinations of Item values for each Color value.

以上是Books Online中的原文.
两者都是配合Group by进行统计,CUBE会对Group by后的每个字段值进行组合统计,而对于ROLLUP,Group by后靠左的字段不会对靠右的字段值产生所有可能的组合统计.(翻译水平有限,汗一个!看例子意会就行)