Step message

STEP N

showplan output displays “STEP N” for every query, where N is an integer, beginning with “STEP 1”. For some queries, Adaptive Server cannot retrieve the results in a single step and breaks the query plan into several steps. For example, if a query includes a group by clause, Adaptive Server breaks it into at least two steps:

One step to select the qualifying rows from the table and to group them, placing the results in a worktable
Another step to return the rows from the worktable

This example demonstrates a single-step query.

select au_lname, au_fname
from authors 
where city = "Oakland"

QUERY PLAN FOR STATEMENT 1 (at line 1).

    STEP 1
        The type of query is SELECT.

        FROM TABLE
            authors
        Nested iteration.
        Table Scan.
        Forward scan.
        Positioning at start of table.
        Using I/O Size 2 Kbytes for data pages.
        With LRU Buffer Replacement Strategy for data pages.

Multiple-step queries are demonstrated following “GROUP BY message”.