Split a column at every whitespace
This should work (sqlfiddle):

SELECT distinct SUBSTRING_INDEX( SUBSTRING_INDEX( transcriptions, ' ', l10.n * 10 + l1.n + 1), ' ', -1) AS transcription
FROM data
CROSS JOIN (
    SELECT 1 AS n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UN ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 UNION ALL SELECT 0
) l1
CROSS JOIN (
    SELECT 1 AS n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9 UNION ALL SELECT 0
) l10
WHERE LENGTH(transcriptions) - LENGTH( REPLACE( transcriptions, ' ', '')) &gt;= l10.n * 10 + l1.n
;


Please note that it may not be extremely efficient. You may consider changing your data model and avoid spliting string using SQL.

Each CROSS JOIN (l1 and l10) create a number table from 1 to 100 (10*10). If strings are longer that 100, extra CROSS JOIN must be added (10*10*10 => 1.000, 10*10*10*10 => 10.000, ...).
The number table is used on characters at each position in the number table and search for spaces.

Sample Data:

CREATE TABLE data(id int, transcriptions varchar(100));
INSERT INTO data(id, transcriptions) VALUES
    (1, 'th i s')
    , (2, 'i s')
    , (3, 's o m e')
    , (4, 't e st')
    , (5, 'd a t a');


Output (no specific order):

transcription
i
s
o
e
a
m
st
t
th
d