LEFT JOIN没有得到想要的结果

Question

So I have 2 tables, first table is clock_in_out I am selecting loggedin and loggedout dates from this table. The second table breaks I am selecting in and out fields. There can be fiedls in clock_in_out that dont match the breaks table... I am joining them on user_id.

The problem is I only get results when breaks has a matching field, I thought left join would get all data from the left table and use fake rows with NULL for non matched data.

Below is my query:

SELECT `clock_in_out`.`loggedin`, `clock_in_out`.`loggedout`, `breaks`.`in`, 
      `breaks`.`out` FROM (`clock_in_out`) 
LEFT JOIN `breaks` ON `clock_in_out`.`user_id` = `breaks`.`user_id`      
WHERE 
      `clock_in_out`.`user_id` = 47 
      AND `breaks`.`user_id` = 47 
      AND `clock_in_out`.`loggedin` LIKE "%2015-03-13%" 
      AND `clock_in_out`.`loggedout` LIKE "%2015-03-13%" 
      AND `breaks`.`in` LIKE "%2015-03-13%"
      AND `breaks`.`out` LIKE "%2015-03-13%"

I am using CodeIgniter's prepared statements for queries and I am unsure how to get the desired result using them: Here is what I have:

    $this->db->select('clock_in_out.loggedin, clock_in_out.loggedout, breaks.in, breaks.out');
    $this->db->from('clock_in_out');

    $this->db->join('breaks','clock_in_out.user_id = breaks.user_id', 'LEFT');

    $this->db->like('breaks.in', $today);
    $this->db->like('breaks.out', $today);
    $this->db->where('clock_in_out.user_id = '.$user_id);
    $this->db->like('clock_in_out.loggedin', $today);
    $this->db->like('clock_in_out.loggedout', $today);

    $q = $this->db->get();

This produces:

SELECT `clock_in_out`.`loggedin`, `clock_in_out`.`loggedout`, `breaks`.`in`, `breaks`.`out` FROM (`clock_in_out`)
LEFT JOIN `breaks` ON `clock_in_out`.`user_id` = `breaks`.`user_id`
WHERE `clock_in_out`.`user_id` = 47
AND `breaks`.`in` LIKE '%2015-03-13%'
AND `breaks`.`out` LIKE '%2015-03-13%'
AND `clock_in_out`.`loggedin` LIKE '%2015-03-13%' AND `clock_in_out`.`loggedout` LIKE '%2015-03-13%'

Query produced from CI answer edits:

SELECT `clock_in_out`.`loggedin`, `clock_in_out`.`loggedout`, `breaks`.`in`, `breaks`.`out` FROM (`clock_in_out`)
LEFT JOIN `breaks` ON `clock_in_out`.`user_id` = `breaks`.`user_id`
WHERE `clock_in_out`.`user_id` = 47 
AND `clock_in_out`.`loggedin` LIKE '%2015-03-13%' 
AND `clock_in_out`.`loggedout` LIKE '%2015-03-13%'

Regards

Answer 1

You get only the matching fields from breaks table because you are using it inside WHERE . Try this:

SELECT `clock_in_out`.`loggedin`, `clock_in_out`.`loggedout`, `breaks`.`in`, 
      `breaks`.`out` FROM (`clock_in_out`) 
LEFT JOIN `breaks` ON 
      `clock_in_out`.`user_id` = `breaks`.`user_id`    
      AND `breaks`.`in` LIKE "%2015-03-13%"
      AND `breaks`.`out` LIKE "%2015-03-13%"
WHERE 
      `clock_in_out`.`user_id` = 47 
      AND `clock_in_out`.`loggedin` LIKE "%2015-03-13%" 
      AND `clock_in_out`.`loggedout` LIKE "%2015-03-13%" 

Update for CodeIgniter

Make sure, that $today is properly escaped to avoid SQL injection.

    $this->db->select('clock_in_out.loggedin, 
                       clock_in_out.loggedout,
                       breaks.in, 
                       breaks.out');
    $this->db->from('clock_in_out');

    $this->db->join('breaks','clock_in_out.user_id = breaks.user_id 
                AND `breaks`.`in` LIKE "%'.$today.'%" 
                AND `breaks`.`out` LIKE "%'.$today.'%"', 'LEFT');

    $this->db->where('clock_in_out.user_id = '.$user_id);
    $this->db->like('clock_in_out.loggedin', $today);
    $this->db->like('clock_in_out.loggedout', $today);

    $q = $this->db->get()

Answer 2

The LEFT JOIN does what you say (selects all the rows from the left table, pairs them with rows full of NULL s when there is no match on the right table).

But then the WHERE conditions come and filter the joined set. And your WHERE conditions on fields of the right-side table ( breaks ) filter out the rows having NULL values on those fields.

Answer 3

Just remove condition for breaks . user_id = 47

SELECT 
`clock_in_out`.`loggedin`,
`clock_in_out`.`loggedout`, 
`breaks`.`in`, 
`breaks`.`out` 
FROM (`clock_in_out`) 
LEFT JOIN `breaks` ON `clock_in_out`.`user_id` = `breaks`.`user_id`
WHERE 
`clock_in_out`.`user_id` = 47 
AND `clock_in_out`.`loggedin` LIKE "%2015-03-13%" 
AND `clock_in_out`.`loggedout` LIKE "%2015-03-13%" 
AND (`breaks`.`in` LIKE "%2015-03-13%"  or `breaks`.`in` is null )
AND (`breaks`.`out` LIKE "%2015-03-13%" or `breaks`.`out` is null)