How to join 2 tables with select and count in single query - sql

Question

I need to join 2 tables (Person and PersonLine). The result should contain id and name column from Person table and count of personlineid column from PersonLine Table for each id. But sql query returns count of all personlineid. Can anyone help to form the sql.
Person:
ID NAME AGE
100 John 25
101 James 30
102 Janet 35
PersonLine:
ID NAME PERSONLINEID
100 John 1
100 John 2
100 John 3
101 James 1
101 James 2
102 Janet 1
SQL:
SELECT P.ID, CNT.COUNT_PERSONLINE, P.NAME
FROM PERSON P
LEFT JOIN PERSONLINE PL
ON P.ID = PL.ID,
(SELECT count(PL.PERSONLINEID) cnt FROM PERSON P LEFT JOIN PERSONLINE PL ON P.ID = PL.ID WHERE
P.ID = PL.ID) cnt
JOIN Table (Expected):
ID COUNT_PERSONLINE NAME
100 3 John
101 2 James
102 1 Janet
JOIN Table (Actual):
ID COUNT_PERSONLINE NAME
100 6 John
101 6 James
102 6 Janet

Answer 1

With your sample data, you don't even need the Person table -- because you seem to have redundant table in the two tables. You should probably fix this, but:
select pl.id, pl.name, count(*)
from personline pl
group by pl.id, pl.name;
Your count is just counting all the rows from the join of the tables -- that would be all the rows. A simple aggregation should suffice, even if you decide that the join is still necessary.
EDIT:
You have several choices with lots of columns in persons. One method is to put them in the group by:
select pl.id, pl.name, p.col1, p.col2, count(*)
from persons p join
personline pl
on p.id = pl.id
group by pl.id, pl.name, p.col1, p.col2
Another method is to do the aggregation before the join:
select p.*, pl.cnt
from person p join
(select pl.id, pl.name, count(*) as cnt
from personline pl
group by pl.id, pl.name
) pl
on p.id = pl.id;
Or, a correlated subquery:
select p.*, (select count(*) from personline pl where p.id = pl.id)
from person;