MySQL 8.0

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CREATE TABLE mytable(
   day      INTEGER  NOT NULL 
  ,shares   INTEGER  NOT NULL
  ,domainid INTEGER  NOT NULL
);
INSERT INTO mytable(day,shares,domainid) VALUES (1571011200,441,1);
INSERT INTO mytable(day,shares,domainid) VALUES (1571097600,443,1);
INSERT INTO mytable(day,shares,domainid) VALUES (1571184000,474,1);
INSERT INTO mytable(day,shares,domainid) VALUES (1571270400,518,1);
INSERT INTO mytable(day,shares,domainid) VALUES (1571184000,849,3);
INSERT INTO mytable(day,shares,domainid) VALUES (1571270400,849,3);
select * from mytable


day
shares
domainid


1571011200
441
1

1571097600
443
1

1571184000
474
1

1571270400
518
1

1571184000
849
3

1571270400
849
3


select 
    day,
    max(case when domainid = 1 then shares end) domainid1_shares,
    max(case when domainid = 3 then shares end) domainid3_shares
from mytable t
group by day


day
domainid1_shares
domainid3_shares


1571011200
441
null

1571097600
443
null

1571184000
474
849

1571270400
518
849

day	shares	domainid
1571011200	441	1
1571097600	443	1
1571184000	474	1
1571270400	518	1
1571184000	849	3
1571270400	849	3

day	domainid1_shares	domainid3_shares
1571011200	441	null
1571097600	443	null
1571184000	474	849
1571270400	518	849