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SAS9 SQL Constraints

23^rd July 2007

With SAS 9, SAS Institute has introduced the sort of integrity constraints that have been bread and butter for relational database SQL programs, but some SAS programmers may find them more restrictive than they might like. The main one that comes to my mind is the following:

proc sql noprint;
    create table a as select a.*,b.var from a left join b on a.index=b.index;
quit;

Before SAS 9, that worked merrily with nary a comment, only for you now to see a warning like this:

WARNING: This CREATE TABLE statement recursively references the target table. A consequence of this is a possible data integrity problem.

In the data step, the following still runs without a complaint:

data a;
    merge a b(keep=index var);
    by index;
run;

On the surface of it, this does look inconsistent. From a database programmer's point of view having to use different source and target datasets is no hardship but seems a little surplus to requirements for a SAS programmer trained to keep down the number of temporary datasets to reduce I/O and keep things tidy, an academic concept perhaps in these days of high processing power and large disks. While adding UNDO_POLICY=NONE to the PROC SQL line does make everything consistent again, I see this as being anathema to a database programming type. Though I do admit to indulging in the override for personal quick and dirty purposes, abiding by the constraint is how I do things for formal purposes like inclusion in an application to a regulatory authority like FDA.

Login Logger plugin

20^th July 2007

The Login Logger WordPress plugin sounds like a great idea and works fine with standard situations. However, go beyond these and things start to go awry. An example is where you have to use unique database table prefixes because you use shared hosting. This is certainly something that I do and it breaks Login Logger. Thankfully, the fix for this is easy enough: just amend the database query on line 22 in the manage.php file as follows:

Before:

$query = "SELECT distinct wp_users.user_login,".$table_name.".username FROM wp_users LEFT OUTER JOIN ".$table_name." ON wp_users.user_login = ".$table_name.".username WHERE ".$table_name.".username IS NULL";

After:

$query = "SELECT distinct " . $table_prefix . "users.user_login,".$table_name.".username FROM " . $table_prefix . "users LEFT OUTER JOIN ".$table_name." ON " . $table_prefix . "users.user_login = ".$table_name.".username WHERE ".$table_name.".username IS NULL";

The issue was caused by hard-coding of the table prefix for the user table, and using the prefix that you yourself have set is the way out of this. What is less easy to resolve is a conflict between the Login Logger and Themed Login plugins. That will take further investigation before I come up with a fix.