MySQL 5.7

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CREATE TABLE sessions
    (`App Type` varchar(11), `Lang` varchar(2), `Session ID` int, `session_time` datetime, `user_id` int)
;
    
INSERT INTO sessions
    (`App Type`, `Lang`, `Session ID`, `session_time`, `user_id`)
VALUES
    #july 2021
    ('browser', 'fr', 46960339, '2021-07-29 00:00:00', 1292997),
    ('browser', 'es', 46960407, '2021-07-29 00:00:00', 1055040),
    ('pwa_android', 'fr', 46960412, '2021-07-29 00:00:00', 1120109),
    ('browser', 'fr', 46960391, '2021-07-29 00:00:00', 955480),
    ('pwa_android', 'en', 46960389, '2021-07-29 00:00:00', 800169),
    ('browser', 'es', 46960353, '2021-07-29 00:00:00', 1193745),
    # june 2021
    ('browser', 'fr', 46960339, '2021-06-29 00:00:00', 1292997),
    ('browser', 'es', 46960407, '2021-06-29 00:00:00', 1055040),
    ('pwa_android', 'fr', 46960412, '2021-06-29 00:00:00', 1120109),
    ('browser', 'fr', 46960391, '2021-06-29 00:00:00', 955480),
    ('pwa_android', 'en', 46960389, '2021-06-29 00:00:00', 800169),
    ('browser', 'es', 46960353, '2021-06-29 00:00:00', 12345),
    # june 2020
    ('browser', 'fr', 46960339, '2020-06-29 00:00:00', 1292997),
    ('browser', 'es', 46960407, '2020-06-29 00:00:00', 1055040),
    ('pwa_android', 'fr', 46960412, '2020-06-29 00:00:00', 1120109),
    ('browser', 'fr', 46960391, '2020-06-29 00:00:00', 955480),
    ('pwa_android', 'en', 46960389, '2020-06-29 00:00:00', 800169),
    ('browser', 'es', 46960353, '2020-06-29 00:00:00', 54321)
;

SELECT * FROM sessions;

CREATE TABLE unique_open_emails
    (`date` datetime, `lang` varchar(2), `user_id` int)
;
    
INSERT INTO unique_open_emails
    (`date`, `lang`, `user_id`)
VALUES
    ('2016-04-12 00:00:00', 'fr', 115434),
    ('2016-04-13 00:00:00', 'fr', 11357),
    ('2016-04-13 00:00:00', 'fr', 137481),
    ('2016-04-13 00:00:00', 'fr', 10296),
    ('2016-04-13 00:00:00', 'fr', 125772),
    ('2016-04-13 00:00:00', 'fr', 955480),
    ('2016-04-13 00:00:00', 'fr', 9269),
    ('2016-04-13 00:00:00', 'fr', 90716),
    ('2016-04-13 00:00:00', 'fr', 26330),
    ('2016-04-13 00:00:00', 'fr', 89072),
    ('2016-04-13 00:00:00', 'fr', 87416),
    ('2016-04-13 00:00:00', 'fr', 88358),
    ('2016-04-13 00:00:00', 'fr', 102515),
    ('2016-04-13 00:00:00', 'fr', 89867),
    ('2016-04-13 00:00:00', 'fr', 119146),
    ('2016-04-13 00:00:00', 'fr', 133316),
    ('2016-04-13 00:00:00', 'fr', 90095),
    ('2016-04-13 00:00:00', 'fr', 16510),
    ('2016-04-13 00:00:00', 'fr', 21530),
    ('2016-04-13 00:00:00', 'fr', 81581),
    ('2016-04-13 00:00:00', 'es', 54321),
    ('2016-04-13 00:00:00', 'fr', 29363),
    ('2016-04-13 00:00:00', 'fr', 90326),
    ('2016-04-13 00:00:00', 'fr', 23961),
    ('2016-04-13 00:00:00', 'fr', 89000),
    ('2016-04-13 00:00:00', 'fr', 9484),
    ('2016-04-13 00:00:00', 'fr', 11845),
    ('2016-04-13 00:00:00', 'fr', 41231),
    ('2016-04-13 00:00:00', 'fr', 588),
    ('2016-04-13 00:00:00', 'fr', 16678),
    ('2016-04-13 00:00:00', 'fr', 19674),
    ('2016-04-13 00:00:00', 'fr', 130113),
    ('2016-04-13 00:00:00', 'fr', 84719),
    ('2016-04-13 00:00:00', 'fr', 123252),
    ('2016-04-13 00:00:00', 'fr', 4676),
    ('2016-04-13 00:00:00', 'fr', 113636),
    ('2016-04-13 00:00:00', 'fr', 17452),
    ('2016-04-13 00:00:00', 'fr', 136544),
    ('2016-04-13 00:00:00', 'fr', 15917),
    ('2016-04-13 00:00:00', 'fr', 82787),
    ('2016-04-13 00:00:00', 'fr', 81620),
    ('2016-04-13 00:00:00', 'fr', 135298),
    ('2016-04-13 00:00:00', 'fr', 15643),
    ('2016-04-13 00:00:00', 'fr', 80981),
    ('2016-04-13 00:00:00', 'fr', 51827),
    ('2016-04-13 00:00:00', 'fr', 90554),
    ('2016-04-13 00:00:00', 'fr', 10277),
    ('2016-04-13 00:00:00', 'fr', 24432),
    ('2016-04-13 00:00:00', 'fr', 6651),
    ('2016-04-13 00:00:00', 'fr', 64106),
    ('2016-04-13 00:00:00', 'fr', 119080),
    ('2016-04-13 00:00:00', 'fr', 72659),
    ('2016-04-13 00:00:00', 'fr', 130004),
    ('2016-04-13 00:00:00', 'fr', 22320),
    ('2016-04-13 00:00:00', 'fr', 136966),
    ('2016-04-13 00:00:00', 'fr', 11317),
    ('2016-04-13 00:00:00', 'fr', 79031),
    ('2016-04-13 00:00:00', 'fr', 90800),
    ('2016-04-13 00:00:00', 'fr', 16149),
    ('2016-04-13 00:00:00', 'fr', 61463),
    ('2016-04-13 00:00:00', 'fr', 5383),
    ('2016-04-13 00:00:00', 'fr', 87674),
    ('2016-04-13 00:00:00', 'fr', 10223),
    ('2016-04-13 00:00:00', 'fr', 88100),
    ('2016-04-13 00:00:00', 'fr', 91691),
    ('2016-04-13 00:00:00', 'fr', 89423),
    ('2016-04-13 00:00:00', 'fr', 126),
    ('2016-04-13 00:00:00', 'fr', 86858),
    ('2016-04-13 00:00:00', 'fr', 1419),
    ('2016-04-13 00:00:00', 'fr', 89849),
    ('2016-04-13 00:00:00', 'fr', 15721),
    ('2016-04-13 00:00:00', 'fr', 86444),
    ('2016-04-13 00:00:00', 'fr', 130822),
    ('2016-04-13 00:00:00', 'fr', 73991),
    ('2016-04-13 00:00:00', 'fr', 113969),
    ('2016-04-13 00:00:00', 'fr', 16779),
    ('2016-04-13 00:00:00', 'fr', 71267),
    ('2016-04-13 00:00:00', 'fr', 61067),
    ('2016-04-13 00:00:00', 'fr', 89081),
    ('2016-04-13 00:00:00', 'fr', 24815),
    ('2016-04-13 00:00:00', 'fr', 91928),
    ('2016-04-13 00:00:00', 'fr', 13071),
    ('2016-04-13 00:00:00', 'fr', 1942),
    ('2016-04-13 00:00:00', 'fr', 44012),
    ('2016-04-13 00:00:00', 'fr', 52049),
    ('2016-04-13 00:00:00', 'fr', 6626),
    ('2016-04-13 00:00:00', 'fr', 7034),
    ('2016-04-13 00:00:00', 'fr', 20442),
    ('2016-04-13 00:00:00', 'fr', 75422),
    ('2016-04-13 00:00:00', 'fr', 16673),
    ('2016-04-13 00:00:00', 'fr', 17325),
    ('2016-04-13 00:00:00', 'fr', 7898),
    ('2016-04-13 00:00:00', 'fr', 85226),
    ('2016-04-13 00:00:00', 'fr', 136557),
    ('2016-04-13 00:00:00', 'fr', 134423),
    ('2016-04-13 00:00:00', 'fr', 68723),
    ('2016-04-13 00:00:00', 'en', 118331),
    ('2016-04-13 00:00:00', 'fr', 91298),
    ('2016-04-13 00:00:00', 'fr', 136046),
    ('2016-04-13 00:00:00', 'fr', 136891),
    ('2016-04-13 00:00:00', 'fr', 9169),
    ('2016-04-13 00:00:00', 'fr', 88946),
    ('2016-04-13 00:00:00', 'fr', 115919),
    ('2016-04-13 00:00:00', 'fr', 44492),
    ('2016-04-13 00:00:00', 'fr', 89783),
    ('2016-04-13 00:00:00', 'fr', 137482),
    ('2016-04-13 00:00:00', 'fr', 10072),
    ('2016-04-13 00:00:00', 'fr', 38636),
    ('2016-04-13 00:00:00', 'fr', 11227),
    ('2016-04-13 00:00:00', 'fr', 108310),
    ('2016-04-13 00:00:00', 'fr', 4700),
    ('2016-04-13 00:00:00', 'fr', 17976),
    ('2016-04-13 00:00:00', 'fr', 8580),
    ('2016-04-13 00:00:00', 'fr', 91316)
;

SELECT 


App Type
Lang
Session ID
session_time
user_id


browser
fr
46960339
2021-07-29 00:00:00
1292997

browser
es
46960407
2021-07-29 00:00:00
1055040

pwa_android
fr
46960412
2021-07-29 00:00:00
1120109

browser
fr
46960391
2021-07-29 00:00:00
955480

pwa_android
en
46960389
2021-07-29 00:00:00
800169

browser
es
46960353
2021-07-29 00:00:00
1193745

browser
fr
46960339
2021-06-29 00:00:00
1292997

browser
es
46960407
2021-06-29 00:00:00
1055040

pwa_android
fr
46960412
2021-06-29 00:00:00
1120109

browser
fr
46960391
2021-06-29 00:00:00
955480

pwa_android
en
46960389
2021-06-29 00:00:00
800169

browser
es
46960353
2021-06-29 00:00:00
12345

browser
fr
46960339
2020-06-29 00:00:00
1292997

browser
es
46960407
2020-06-29 00:00:00
1055040

pwa_android
fr
46960412
2020-06-29 00:00:00
1120109

browser
fr
46960391
2020-06-29 00:00:00
955480

pwa_android
en
46960389
2020-06-29 00:00:00
800169

browser
es
46960353
2020-06-29 00:00:00
54321


SELECT MIN(date_email, date_activity) FROM 
    (
        SELECT date FROM unique_open_emails
        ORDER BY date ASC LIMIT 1;
    ) AS date_email,
    (
        SELECT session_time FROM sessions
        ORDER BY session_time ASC LIMIT 1;
    ) AS date_activity
)
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' date_activity) FROM 
    (
        SELECT date FROM unique_open_emails
        ' at line 1

select lang, count(distinct user_id)
from ((select user_id, lang
       from sessions
       where session_time > now() - interval 1 year
      ) union all
      (select user_id, lang
       from unique_open_emails
       where date > now() - interval 1 year
      )
     ) u
group by lang;


lang
count(distinct user_id)


en
1

es
3

fr
3

App Type	Lang	Session ID	session_time	user_id
browser	fr	46960339	2021-07-29 00:00:00	1292997
browser	es	46960407	2021-07-29 00:00:00	1055040
pwa_android	fr	46960412	2021-07-29 00:00:00	1120109
browser	fr	46960391	2021-07-29 00:00:00	955480
pwa_android	en	46960389	2021-07-29 00:00:00	800169
browser	es	46960353	2021-07-29 00:00:00	1193745
browser	fr	46960339	2021-06-29 00:00:00	1292997
browser	es	46960407	2021-06-29 00:00:00	1055040
pwa_android	fr	46960412	2021-06-29 00:00:00	1120109
browser	fr	46960391	2021-06-29 00:00:00	955480
pwa_android	en	46960389	2021-06-29 00:00:00	800169
browser	es	46960353	2021-06-29 00:00:00	12345
browser	fr	46960339	2020-06-29 00:00:00	1292997
browser	es	46960407	2020-06-29 00:00:00	1055040
pwa_android	fr	46960412	2020-06-29 00:00:00	1120109
browser	fr	46960391	2020-06-29 00:00:00	955480
pwa_android	en	46960389	2020-06-29 00:00:00	800169
browser	es	46960353	2020-06-29 00:00:00	54321