Insert into table with multiple select including select distinct from two tables - sql

Question

I have two SQL Server tables (simplified) below:
Table1
| productname | certno | expdate | company
+-------------+--------+------------+---------
| abc | 123 | 2020-01-01 | ABC
| def | 123 | 2020-01-01 | ABC
| qwe | 456 | 2020-01-02 | ABC
| asd | 999 | 2020-02-02 | DEF
| .. | .. | .. | ..
Table2
| companyid | company
+-----------+---------
| 1 | ABC
| 2 | DEF
| .. | ..
And I need to insert data from these 2 tables into another table for distinct certno, Table3 should be like this:
| certid | companyid | certno | expdate | createddate | is_null
+--------+-----------+--------+------------+-------------+---------
| 1 | 1 | 123 | 2020-01-01 | 2020-09-12 | 1
| 2 | 1 | 456 | 2020-01-02 | 2020-09-12 | 1
| 3 | 2 | 999 | 2020-02-02 | 2020-09-12 | 1
| .. | .. | .. | .. | .. | ..
I'm currently using this query, I need to create a script so that next batch of update is just in one query.
insert into Table3 (certno, expdate, is_null)
select distinct certno, expdate
from Table1
where company like '%ABC%';
--then I will update Table3 to complete it
update Table3
set companyid = '1',
createddate = getdate(),
is_null = '1'
where is_null is null; --edited**
--then repeat the above until I have all companies registered as companyid in Table3
But this will be a hassle when it involved more companies and lots of data and I was thinking of using multiple select including select distinct but I'm stuck right here:
insert into Table3 (companyid, certno, expdate, createddate)
select
(select companyid from Table2
where company in (select company from Table1)
),
(select distinct certno),
expdate,
getdate()
from Table1;
I did not run the script to see whether it works or not because I don't want to mess up the Table3 data and I feel that the script is not going to work.
Is there any way to just run the query in one script?

Answer 1

I think you want insert . . . select with join:
insert into Table3 (companyid, certno, expdate, createddate, is_null)
select distinct t2.companyid, t1.certno, t1.expdate, getdate(), 1
from Table1 t1 join
Table2 t2
on t1.company = t2.company
where t1.company like '%ABC%';
You can remove the where clause to insert all companies in one insert.

Answer 2

Looks like you just need to expand the columns in the SELECT:
INSERT INTO dbo.Table3 (certno, expdate, companyid, createdate)
SELECT DISTINCT
certno,
expdate,
company,
GETDATE()
FROM dbo.Table1;