Insert/update a flag depending on values matched between to tables - sql

Question

I want to make a procedure where:
If an ID exists in table B but not in Table A code with be inser/updated to 0.
Else if the ID exists in both table code field will be insert/updated to 1.
I have two tables, for example:
Table A Table B
+----+--+--+----+------+
| ID | | | Id | Code |
+----+--+--+----+------+
| 1 | | | 1 | 0 |
| 2 | | | 2 | 0 |
| 3 | | | 3 | 0 |
| 4 | | | 4 | 0 |
| | | | 5 | 0 |
| | | | 6 | 0 |
+----+--+--+----+------+
Can you please help me with that?
Table B in the end should be like this:
+----+------+
| Id | Code |
+----+------+
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 0 |
| 6 | 0 |
+----+------+

Answer 1

Something like this: make left join to generate values of table B, which not present in table A, then merge to update column Code.
merge into table_b
using (select b.id, case when a.id is null then 0 else 1 end code
from table_b b left join table_a a on a.id = b.id) t
on (t.id = table_b.id)
when matched then update
set code = t.code

Answer 2

You can use MERGE:
MERGE into tableB B
USING tableA A
ON (a.id = b.id)
WHEN MATCHED THEN
UPDATE SET code = 1
WHEN NOT MATCHED THEN
INSERT (id,code) values (a.id, 0)

Answer 3

Please find the answer below for your question...,
create table TABLEA (ID int);
insert into TABLEA (ID) values (1);
insert into TABLEA (ID) values (2);
insert into TABLEA (ID) values (3);
insert into TABLEA (ID) values (4);
insert into TABLEA (ID) values (5);
create table TABLEB (ID int, code int);
insert into TABLEB (ID,code) values (1,0);
insert into TABLEB (ID,code) values (2,0);
insert into TABLEB (ID,code) values (3,0);
insert into TABLEB (ID,code) values (4,0);
insert into TABLEB (ID,code) values (5,0);
insert into TABLEB (ID,code) values (6,0);
insert into TABLEB (ID,code) values (7,0);
insert into TABLEB (ID,code) values (8,0);
UPDATE TABLEB SET CODE=1 FROM TABLEB B INNER JOIN TABLEA as A on A.id=B.id;
SELECT * FROM TABLEB;
ID CODE
1 1
2 1
3 1
4 1
5 1
6 0
7 0
8 0