Check if value is not null and not empty in a select query

Question

I have created a function in Postgresql and specified the returned type as TABLE (id uuid, data boolean).

This is the code that I have tried:

BEGIN
    RETURN QUERY SELECT table.id, (table.data <> '') as data FROM table;
END

But it will return NULL for "data" when data is NULL in the table. I was expecting it to return FALSE.

Data column is storing a JSON and I am trying to check if the stored value is not null and not empty

How can I make this code work?

user330315 · Accepted Answer · 2021-11-23 13:47:51Z

1

Use is distinct from to use a null-safe comparison:

SELECT table.id, table.data is distinct from '' as data 
FROM table;

Another option is to treat an empty string like null:

SELECT table.id, nullif(table.data, '') is not null as data 
FROM table;

answered Nov 23, 2021 at 13:47

user330315

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1 Comment

I just thought that <> also checks for NULL after reading this. Your second solution solved my problem. Thanks.