Database Reference
In-Depth Information
Alternatively, clear the parameter's value in the environment before generating the field:
param
(
-
name
=>
"keyword"
,
-
value
=>
""
);
print
textfield
(
-
name
=>
"keyword"
,
-
size
=>
20
);
20.10. Generating Previous-Page and Next-Page Links
Problem
A statement matches so many rows that displaying them all in a single web page produces
an unwieldy result.
Solution
Split the statement output across several pages and include links that enable the user to
navigate among pages.
Discussion
If a statement matches a large number of rows, showing them all in a single web page
can result in a display that's difficult to navigate. For such cases, it can be more convenient
for the user if you split the result among multiple pages. A paged display avoids over‐
whelming the user with too much information, but is more difficult to implement than
a single-page display.
A paged display typically is used in a search context to present rows that match the
search parameters supplied by the user. To simplify things, the examples in this recipe
don't have any search interface. Instead, they implement a paged display that presents
10 rows at a time from the result of a fixed statement:
SELECT
name
,
abbrev
,
statehood
,
pop
FROM
states
ORDER
BY
name
;
MySQL makes it easy to select just a portion of a result set: add a
LIMIT
clause that
indicates which rows you want. The two-argument form of
LIMIT
takes values indicating
how many rows to skip at the beginning of the result set, and how many to select. The
statement to select a section of the
states
table thus becomes:
SELECT
name
,
abbrev
,
statehood
,
pop
FROM
states
ORDER
BY
name
LIMIT
skip
,
select
;
One issue, then, is to determine the proper values of
skip
and
select
for any given
page. Another is to generate the links that point to other pages or the statement result.
This second issue presents you with a choice: which paging style should you use for the
links?
