Database trigger | Technology Tales

Redirecting a WordPress site to its home page when its loop finds no posts

5^th November 2022

Since I created a bespoke theme for this site, I have been tweaking things as I go. The basis came from the WordPress Theme Developer Handbook, which gave me a simpler starting point shorn of all sorts of complexity that is encountered with other themes. Naturally, this means that there are little rough edges that need tidying over time.

One of these is dealing with errors on the site, like when content is not found. This could be a wrong address or a search query that finds no matching posts. When that happens, there is a redirection to the home page using some simple JavaScript within the loop fallback code enclosed within script start and end tags (including the whole code triggers the action from this post so it cannot be shown here):

location.href="[blog home page ]";

The bloginfo function can be used with the url keyword to find the home page, avoiding hard-coding. For now, this works so long as JavaScript is enabled, but a more robust approach may come in time. It is not possible to do a PHP redirect because of the nature of HTTP: when headers have been sent, it is not possible to do server redirects. At this stage, things become client side, so using JavaScript is one way to go instead.

Updating Oracle data tables that have associated sequence objects

3^rd May 2007

Here’s something that I want to put somewhere for future reference before I forget it: keep sequences associated with Oracle data tables up to date while adding records. Given that it took me a while to find it, it might come in useful for someone else too.

The first thing is to update the sequence itself:

SELECT TABLE_SEQ.NEXTVAL FROM DUAL;

Dual is a handy single record table that you can use to update sequences. Use the actual associated table itself if you like to see that sequence number rocket…

The next thing is to use the new value to assign a table ID as part of an INSERT statement:

INSERT INTO “TABLE” VALUES (TABLE_SEQ.CURRVAL, 1, ‘Test value’);

Learning about Oracle

20^th April 2007

My work in the last week has put me on something of a learning about Oracle. This is down to my needing to add file metadata to a database as part of an application that I am developing. Since the application is written in SAS, I am using SAS/Access for Oracle to update the database using SQL pass-through statements written in Oracle SQL. I am used to SAS SQL and there is commonality between it and Oracle’s implementation, which is a big help. Nevertheless, there, of course, are things specific to the Oracle world about which I have needed to learn. My experiences have introduced me to concepts like triggers, sequences, constraints, primary keys, foreign keys and the like. In addition, I have also seen the results of database normalisation at first hand.

Using Oracle’s SQL Developer has been a great help in my endeavours, thanks to its online help and the way that you can view database objects in an easy-to-use manner. It also runs SQL scripts, giving you a feel for how Oracle works, and anyone can download it for free upon registration on the Oracle website. Additionally, I have installed the Oracle 10g database Express edition at home, which serves as a valuable personal learning resource. That is another free download from Oracle’s website.

My Safari bookshelf has been another invaluable resource, providing access to O’ Reilly’s Oracle books. Of these, Mastering Oracle SQL has proved particularly useful, and I made a journey to Manchester after work this evening (Waterstones on Deansgate is open until 21:00 on weekdays) to see if I could acquire a copy. While that quest was to prove fruitless, I now have got the doorstop that is Oracle Database 10g: The Complete Reference from The Oracle Press, an imprint of Osborne and McGraw Hill. Since I needed a broader grounding in all things Oracle, this should help. Usefully, it also covers SQL, but the aforementioned O’ Reilly volume could return to the wish list if that provision is insufficient.