Gbase8s database select has order by Clause 6

ORDER SIBLINGS BY Clause

ORDER SIBLINGS BY Clause is valid only in hierarchical queries . Optional SIBLINGS Keyword specifies that the parent row first

Sort , And then sort the child rows of each parent row of each level within the hierarchy .

Some lines have SIBLINGS BY A repeating list of values in the specified column after the keyword , These rows have the same list of values and phase

The rows of the same parent row are arbitrarily sorted . If the hierarchical query contains no SIBLINGS Keywords ORDER BY Son

sentence , According to those who follow ORDER BY Keyword to arrange the order of rows . In hierarchical queries , It's not necessary

ORDER BY Clause , Don't need to, ORDER BY Clause ORDER SIBLINGS BY Options .

The hierarchical query in the following example returns a subset of rows in the hierarchical dataset , Its root is Goyal, Such as the theme Hierarchical query clause in

As listed . This query includes ORDER SIBLINGS BY Clause according to name For those who report to the same manager

Sort employees ：

SELECT empid, name, mgrid, LEVEL

FROM employee

START WITH name = ‘Goyal’

CONNECT BY PRIOR empid = mgrid

ORDER SIBLINGS BY name;

Sort the rows returned by this query in the following order ：

empid name mgrid level

16 Goyal 17 1

12 Henry 16 2

7 O’Neil 12 3

9 Shoeman 12 3

8 Smith 12 3

14 Scott 16 2

11 Zander 16 2

6 Barnes 11 3

5 McKeough 11 3

9 row(s) retrieved.

Here it is ,START WITH Clause returns... At the root of this level Goyal That's ok . Two subsequent CONNECT BY step

（ stay level The pseudo column is marked with 2 and 3） Returns the set of three sibling rows ：

Henry、Scott and Zander His parents are Goyal Brother ;

O’Neil、Shoeman and Smith His parents are Henry Brother ;

Barnes and McKeough Make their parents Zander Brother .

Next CONNECT BY Step did not return line , Because it conforms to level = 3 The rows of are leaf nodes in this hierarchy . In this check

At this execution point of the inquiry , take ORDER SIBLINGS BY Apply to result set , Sort the rows in the above order .

Because of the sort key name by VARCHAR Column , Therefore, the returned rows within each sibling's set follow their

employee.name It's worth it ASCII Sequential arrangement . Sort only those siblings of the leaf node in the hierarchy of the returned row

The results of are concentrated and continuous , Because managers follow the employees who report to them , Not their brother . In this example

The exception is Scott, Its child nodes form an empty set .

ORDER BY In Clause SIBLINGS The key word is right SQL Linguistic ISO Extensions to the standard syntax . If you don't pack

Include valid CONNECT BY Clause of a query or subquery ORDER BY Clause includes SIBLINGS keyword , be

SELECT The statement fails with an error .

To learn more about hierarchical queries and CONNECT BY Clause information , see also Hierarchical query clause .