Data

In[]:=
tab1=Tabular[{{"001",1,2,3},{"002",4,5,6},{"003",7,6,7},{"004",8,9,10},{"005",8,9,10}},{"ID","num 1","num 2","num 3"}]//Dataset
Out[]=
ID
num 1
num 2
num 3
001
1
2
3
002
4
5
6
003
7
6
7
004
8
9
10
005
8
9
10
In[]:=
tab2=Tabular[{{"001",0.1,0.3},{"002",0.99,0.1},{"003",1.01,1.67},{"005",0.4,0.3}},{"ID","num 4","num 5"}]//Dataset
Out[]=
ID
num 4
num 5
001
0.1
0.3
002
0.99
0.1
003
1.01
1.67
005
0.4
0.3

Joined

In[]:=
JoinAcross[tab1,tab2,"ID","Left"]//Dataset
Out[]=
ID
num 1
num 2
num 3
num 4
num 5
001
1
2
3
0.1
0.3
002
4
5
6
0.99
0.1
003
7
6
7
1.01
1.67
004
8
9
10
—
—
005
8
9
10
0.4
0.3