LucidDbAppLib TOPN

From Eigenpedia

Contents 1 Syntax 2 Purpose 2.1 Parameters 3 Examples 4 Source Code

Syntax

select * from table(
    applib.topn(IN_CURSOR, NUMBER_OF_ROWS)
);

Purpose

Extract the first <NUMBER_OF_ROWS> rows of a table.

Parameters

Input:

• IN_CURSOR cursor: cursor to the original table.
• NUMBER_OF_ROWS integer: the number of rows from the IN_CURSOR to return.

Output:

• The <NUMBER_OF_ROWS> first rows of <IN_CURSOR>.
  • If <NUMBER_OF_ROWS> is greater than the number of rows in <IN_CURSOR> then all rows are returned.
  • If <NUMBER_OF_ROWS> is less than or equal to 0 no rows are returned.

Exceptions

• NullPointerException if <NUMBER_OF_ROWS> is null

Examples

select schema_name from sys_root.dba_schemas order by schema_name;                                             
+---------------------+
|     SCHEMA_NAME     |
+---------------------+
| APPLIB              |
| INFORMATION_SCHEMA  |
| JDBC_METADATA       |
| MGMT                |
| SQLJ                |
| SYS_BOOT            |
| SYS_ROOT            |
| TEMP                |
+---------------------+
select * from table(applib.topn(cursor(
  select schema_name from sys_root.dba_schemas order by schema_name
  ), 2));
+---------------------+
|     SCHEMA_NAME     |
+---------------------+
| APPLIB              |
| INFORMATION_SCHEMA  |
+---------------------+

Source Code

http://p4web.eigenbase.org/open/dev/luciddb/src/com/lucidera/luciddb/applib/cursor/TopNUdx.java