加入mysql表并在为空时获取所有记录

Question

im having 3 tables

venture - stores details about ventures
venture_buys - details about the venture purchases
users - details about the users

im using the below query to join all the 3 tables and show the details in a block

SELECT `a`.`user_id`, `a`.`g_id`,`b`.`first_name`, `b`.`last_name`,  `a`.`description`, `a`.`title`, `a`.`location`,b.title, sum(c.mt_qty) as m_qty
        FROM `users` `a`
        LEFT JOIN `venture` `b` ON `b`.`id`=`a`.`user_id`
        LEFT JOIN `venture_buys` `c` ON `c`.`g_id`=`a`.`g_id`
        ORDER BY `c`.`g_id` ASC

the problem that im having is venture_buys has details only if its been purchased or else its always empty. i use that table to calculate the purchased quantity. when i try to add and show the ventures it does not show the record unless venture_buys has a record.

is there way to change the query or write a condition to get all the records even if there is no record in venture_buy?

Answer 1

You can try this, mate:

SELECT
    u.user_id, u.g_id,
    v.first_name, v.last_name,
    u.description, u.title, u.location,
    v.title, SUM(vb.mt_qty) AS m_qty
FROM
    venture v
    INNER JOIN users u ON u.id = v.id
    INNER JOIN venture_buys ON vb.g_id = u.g_id
GROUP BY
    vb.g_id
ORDER BY
    vb.g_id ASC; 

Answer 2

Making a lot of assumptions on the structure, maybe this is what you want to do:

SELECT `a`.`user_id`, `a`.`g_id`,`b`.`first_name`, `b`.`last_name`,  `a`.`description`, `a`.`title`, `a`.`location`,`b`.`title`, `c`.`sum_qty` as m_qty
        FROM `users` `a`
        LEFT JOIN `venture` `b` ON `b`.`id`=`a`.`user_id`
        LEFT JOIN (SELECT `g_id`,sum(`mt_qty`) AS `sum_qty` FROM `venture_buys` GROUP BY `g_id`) AS `c` ON `c`.`g_id`=`a`.`g_id`
        ORDER BY `c`.`g_id` ASC

Don't know why I followed those illogical allias names...