如何从两个 sql 查询结果中获取结果

Question

I"m using SET @runtot:=0 at the top of my SQL code and it gets 2 query results:

The first one is:

MySQL returned an empty result set (ie zero rows). (Query took 0.0002 seconds.)

The second is:

Showing rows 0 - 7 (8 total, Query took 0.0058 seconds.)

how can i get the results of the second query only?

here is my SQL code:

SET @runtot:=0;

SELECT 
fname,
lname,
guests,
phone

FROM (

(SELECT *, 0 AS rt FROM guests_table WHERE status = 2)
UNION
 (SELECT *, (@runtot := @runtot + rsvp.guests) AS rt
 FROM 
    (SELECT *
     FROM  guests_table
     WHERE status != 2
     ) AS rsvp
WHERE @runtot + rsvp.guests <= 4)
    )rsvp

ORDER BY rsvp.id ASC

Answer 1

You can set the parameters in the query:

SELECT fname, lname, guests, phone
FROM ((SELECT *, 0 AS rt FROM guests_table WHERE status = 2)
      UNION
      (SELECT *, (@runtot := @runtot + rsvp.guests) AS rt
       FROM (SELECT *
             FROM  guests_table
             WHERE status != 2
            ) AS rsvp
       WHERE @runtot + rsvp.guests <= 4)
      ) rsvp CROSS JOIN
      (SELECT @runtot := 0) params
ORDER BY rsvp.id ASC;

Note that the use of variables in SELECT queries like this has been deprecated. In MySQL 8+, you should be using window functions.

In addition, the "running sum" is reading the rows in an arbitrary order. There is no guarantee that the result will be in the same order as the results.

If you want further help with the query, ask a new question. Provide sample data, desired results, and a clear explanation of the logic.