Using Map Tips and Ruled Expression in QGIS?

Question

QGIS 2.18.5

I'm trying to add a condition to my expression in my html/css map tips where if a value is 'null', the result will show 'no data available'.

I've got a screenshot of my map tip so far for a feature with populated values (the date and the number of years). Not all the features have a date and integer associated with them.

What do I add to the code below?

<h1> [%"Local Auth"%] </h1> <h3> Date LAP Adopted</h3> <p> [% "Local Pl_1" %] </p> <h3> Five Year Housing Supply</h3> <p> [% "5 YHLS (#)" %] </p>

I tried

<h3> Date LAP Adopted</h3> <p> [%CASE WHEN "Local Pl_1" = ' ' THEN 'No Data Available' END%] </p>

but no luck.

Answer 1

Try coalesce()

<h1> [%"Local Auth"%] </h1>
<h3> Date LAP Adopted</h3> <p> [% coalesce("Local Pl_1", 'No Data Available') %] </p>
<h3> Five Year Housing Supply</h3> <p> [% "5 YHLS (#)" %] </p>

Answer 2

If your data it truly Null (and not a white space), then use IS NULL to detect it.

[%CASE WHEN  "Local Pl_1" IS NULL THEN 'No Data Available'
end%]

If the content of the field Local Pl_1 is to be displayed if it set (i.e. it is not null for some records), you can instruct QGIS to show it:

[%CASE WHEN  "Local Pl_1" IS NULL THEN 'No Data Available' ELSE  "Local Pl_1" 
end%]

--> if record 1 has a null "Local Pl_1" value, then No Data Available is displayed. If record 2 has the value "Local Pl_1" = Test, then Test is displayed in the maptip.