Question

I have a query with duplicate expressions in it. Could it be written more compact?

select id from `vacature_saved_searches`
       where `saved_search_interval` = 1 and 
              DAYOFWEEK(CURDATE()) BETWEEN 2 AND 6 and 
              `last_processing_started_datetime` < CURDATE() - INTERVAL 1 HOUR
UNION
select id from `vacature_saved_searches` 
       where `saved_search_interval` = 2 and 
              DAYOFWEEK(CURDATE()) IN (2, 4, 6) and 
             `last_processing_started_datetime` < CURDATE() - INTERVAL 1 HOUR
UNION
select id from `vacature_saved_searches` 
       where `saved_search_interval` = 3 and 
              DAYOFWEEK(CURDATE()) = 3 AND 
              `last_processing_started_datetime` < CURDATE() - INTERVAL 1 HOUR
UNION
select id from `vacature_saved_searches` 
       where `saved_search_interval` = 4 and 
              DAYOFWEEK(CURDATE()) = 3 and 
              DAYOFMONTH(CURDATE()) BETWEEN 1 AND 7 and 
              `last_processing_started_datetime` < CURDATE() - INTERVAL 1 HOUR;

Answer 1

You can use a combination of DISTINCT and rephrasing the query to use OR clauses rather than unions:

select DISTINCT id from `vacature_saved_searches`
   where ((`saved_search_interval` = 1 and DAYOFWEEK(CURDATE()) BETWEEN 2 AND 6) OR
         (`saved_search_interval` = 2 and DAYOFWEEK(CURDATE()) IN (2, 4, 6)) OR 
         (`saved_search_interval` = 3 and DAYOFWEEK(CURDATE()) = 3) OR 
         (`saved_search_interval` = 4 and DAYOFWEEK(CURDATE()) = 3 and 
             DAYOFMONTH(CURDATE()) BETWEEN 1 AND 7))
         AND `last_processing_started_datetime` < CURDATE() - INTERVAL 1 HOUR;