Question

I have a table activity_types which contains the text for activities e.g.
New project has been assigned to {user} with name {project}
New discussion has been posted by {client} on {project}
Project {project} has been closed by {user}
A draft has been approved by {client} on {project}
and so on

I have another table in which the id of these texts has been populated.

Now my requirement is to fetch these by replacing the text within {} with their actual values like {client} should be replaced with client name, {project} should be replaced with project name.

I have tried using nested replace mysql function but it returns null string. Here is my query

SELECT      REPLACE(REPLACE(REPLACE(att.type_text, '{project}', p.project_business_name), '{user}', u.user_fullname), '{client}', c.client_name) AS activity, a.*
FROM        activities a
LEFT JOIN   activity_types AS att ON att.type_id = a.activity_type
LEFT JOIN   users u ON u.user_id = a.activity_user AND a.activity_user IS NOT NULL
LEFT JOIN   projects p ON p.project_id = a.activity_project AND p.project_is_removed = '0'
LEFT JOIN   clients c ON c.client_id = a.activity_client AND a.activity_client IS NOT NULL;

The problem is that if i replace the c.client_name with static text it works fine but when i replace the static string with c.client_name it return null in activities which does not have {client}. Any guesses where am i doing wrong?

Answer 1

try adding COALESCE on the column

...,COALESCE(c.client_name, ''),

basically if the column (c.client_name) is null, it will be replace with empty string.

what happens is that when part of the string is replace with null, the whole string becomes null.