In my Ruby on Rails app I'm using blazer(https://github.com/ankane/blazer) and I have the following sql query:
SELECT *
FROM survey_results sr
LEFT JOIN clients c ON c.id = sr.client_id
WHERE sr.client_id = {client_id}
This query works really well. But I need to add conditional logic to check if client_id variable is present. If yes then I filter by this variable, if not then I not launching this where clause. How can I do it in PostgreSQL?
Check if its null OR your condition like this:
WHERE {client_id} IS NULL OR sr.client_id = {client_id}
The WHERE clause evaluate as follow: If the variable is empty, then the WHERE clause evaluate to true, and therefore - no filter. If not, it continue to the next condition of the OR
If anyone faced with the psql operator does not exist: bigint = bytea issue, here is my workaround:
WHERE ({client_id} < 0 AND sr.client_id > {client_id}) OR sr.client_id = {client_id}
Please consider that, client_id generally cannot be negative so you can use that information for eleminating the operation cast issue.
My solution:
I use spring data jpa, native query.
Here is my repository interface signature.
@Query(... where (case when 0 in :itemIds then true else i.id in :itemIds end) ...)
List<Item> getItems(@Param("itemIds) List<Long> itemIds)
Prior calling this method, I check if itemIds is null. If yes, I set value to 0L:
if(itemIds == null) {
itemIds = new ArrayList<Long>();
itemIds.add(0L);
}
itemRepo.getItems(itemIds);
My IDs starts from 1 so there is no case when ID = 0.
