使用SQL子查询或JOIN子句进行选择

Question

So I have these tables.

This table stores likes:

Table Name: Action

Id   Creator   Type   Target     <--- The `Target` here is the `Id` in Posts
1    1         like   1
2    2         like   1
3    3         like   1
4    1         like   2

This table stores posts:

Id   Creator
1    1
2    2

The column name Creator in any table refers to the Id column in the Account table (not shown here).

I would like to select the total number of likes that have been given to an account's posts. I have tried the query below but it gave a syntax error.

SELECT count(`Id`) AS Check FROM `Action` WHERE `Type`='like' AND `Target`= (SELECT `Id` FROM `Posts` WHERE `Creator` = '1');

I'm not sure if a JOIN clause would be more appropriate here.

Answer 1

You will get the sums with a join of both tables and GROUP BY and counting the appropriate targets.

SELECT
    p.creator,      
    COUNT(a.target) 
FROM
    posts p
INNER JOIN
    Action a
ON
    a.target = p.id
WHERE
    a.Type = 'like' AND p.creator = 1
GROUP BY
    p.creator;

Answer 2

Here is the SQL

    select a.ID,a.Creator,a.Type,a.Target, Count(p.*)Total
    from Action a 
    join posts p on a.Target=p.Creator
    where 
    a.Type='like'
    and a.Target=1;