An easy way to use the same parameter value repeatedly in a query

[timhunt]

Sometimes, when writing a query, you want to use a single parameter value in several places. Each placeholder being used exactly once is a limitation of the Moodle database system, which we just use as-is, so there is no easy way to do this.

There are tricks you can do. For examle with a single query that joins serveral tables, you can include something like

JOIN (SELECT :my_value AS my_value) input ON 1 = 1

then you can refer to input.my_value everywhere. However, this is tricky to work out, and does not always work (e.g. with UNIONS).

In response to a question about this, I just relalised that we could implemented a work-around.

For example, we could make it that if you have parameters called :my_value, :my_value_copy1, :my_value_copy2, ..., then we only show a single input for 'my value' when someone runs the report, and then we duplicate that value as my_value_copy1, .... That should be feasible.