MySQL first condition match priority - mysql

Question

I have this data
+----+--------+---------------------------------+
| id | fromid | message |
+----+--------+---------------------------------+
| 1 | 1213 | this is just an example |
+----+--------+---------------------------------+
| 2 | 1992 | other random message |
+----+--------+---------------------------------+
| 3 | 1364 | example number three |
+----+--------+---------------------------------+
I need to search data where fromid='1992' or message LIKE '%example%'
if there is any result where fromid matches 1992 value, return this result, and ignore second condition
but if there is no result from first condition (fromid='1992'), return the result from second condition
can I do that on single query?

Answer 1

One way to do it is using a marker, and then limiting the results to the first row. An example using UNION:-
SELECT 1 AS match_type, my_table.*
from my_table
where fromid = 1992
UNION
SELECT 2 AS match_type, my_table.*
from my_table
WHERE message like '%example%'
ORDER BY match_type
LIMIT 1
Down side of this is that it still forces a relatively slow non indexed query using LIKE with a leading wildcard.
The following is an alternative. In most circumstance it would be pointless, but should the check on id be expected to bring back a record almost always, and the check on the LIKE just a very occasional condition (with only a single record ever returned) then it might be worthwhile as it would avoid having the do the slow LIKE condition searched unless necessary.
SELECT COALESCE(id, SELECT MAX(id) from my_table WHERE message like '%example%') AS id,
COALESCE(fromid, SELECT MAX(formed) from my_table WHERE message like '%example%') AS formed,
COALESCE(message, SELECT MAX(message) from my_table WHERE message like '%example%') AS message
FROM
(
SELECT id, fromid, message
FROM (SELECT 1 AS a_cnt) sub0
LEFT OUTER JOIN
(
SELECT id, fromid, message
from my_table
where fromid = 1992
) sub1
) sub2