Condition in a SQL statement-CodePudding

I get this error:

ERROR: syntax error at or near "FROM"
LINE 14: FROM dat.unit du

This is the query:

SELECT
    (SELECT  extract (epoch 
     FROM
         (SELECT avg_freq  
          FROM tlm.data_qa_tele_freq(du.id, null, now()::timestamp - interval '0.5 day', now()::timestamp)) 
    )) AS "ASDF"
FROM 
    dat.unit du

Returns this column:

As you can see it returns null if there is not data and an real number. What I must get is the values which are bigger than 30.

CodePudding user response：

Instead of the CASE statement, you should use a WHERE clause here.

WITH cte AS (
  SELECT
    (SELECT EXTRACT(epoch FROM
        (SELECT avg_freq  
         FROM tlm.data_qa_tele_freq(du.id, 
                                    null, 
                                    now()::timestamp - interval '0.5 day',
                                    now()::timestamp) 
      ) 
    )) AS "ASDF",
  FROM dat.unit du
)
SELECT * 
FROM cte
WHERE "ASDF" > 30

If the "ASDF" field is a string instead of a integer-like value, you need to use the typecasting operation:

WHERE "ASDF"::INTEGER > 30

Also I'd recommend to check the CASE full syntax on the official documentation.