SQL 查询 Postgres 12

Question

I'm doing an inner join on a table like this:

SELECT * 
FROM  patient p
INNER JOIN 
    vaccine v
ON 
    p.vaccine_id =  v.id 

The condition f.vac_1 = mv.id might not been satisfied in the case where a person have not been vaccinated. In such case, I don't want to ignore the row, but instead of displaying the vaccine name (which is the purpose of the inner join) to display an emtpy string.

How can this be done?

Example

Table vaccinne

id	name
1	Moderna
2	Comirnaty
3	Janssen

Table patient

id	name	vaccine_id
1	john	1
2	kermit	2
3	jessica

I'm looking for a query to produce:

id	name	vaccine_id
1	john	Moderna
2	kermit	Comirnaty
3	jessica

Answer 1

If I understand correctly, you want a left join starting with foo :

SELECT * 
FROM foo f LEFT JOIN
     vac v 
     ON f.vac_1 =  mv.id