Select syntax inside WHERE

Question

How do I use SELECT syntax inside WHERE for example I have following code:

SELECT 
    blah...blah..
    ...
WHERE  
(
  (APM_AlertsAndReportsData.ApplicationName = 'instance: tomcat6_noram (SNMP)') AND 
  (APM_AlertsAndReportsData.ComponentName = 'Memory Heap Used (B)') AND 
  (APM_AlertsAndReportsData.StatisticData >= 1908932600)
)

Here I am comparing values if its greater than or equal to 1908932600. I want to use SELECT in place of 1908932600 so it will automatically compare values rather than statically code in query.

Answer 1

You can use a subquery, you just need parentheses around it:

APM_AlertsAndReportsData.StatisticData >= (SELECT ... FROM ...)

Note that it may run slowly depending on what you are doing in your subquery. It might be better to use a JOIN instead.

Answer 2

You need a "correlated subquery" in the WHERE clause:

WHERE  
(
  (APM_AlertsAndReportsData.ApplicationName = 'instance: tomcat6_noram (SNMP)') AND 
  (APM_AlertsAndReportsData.ComponentName = 'Memory Heap Used (B)') AND 
  (APM_AlertsAndReportsData.StatisticData >= (SELECT SomeValue FROM SomeTable))
)