LEFT JOIN只返回一半所需要的结果

Question

我目前有：

SELECT * FROM submissions AS s 
    LEFT JOIN submission_category AS sc ON s.submission_category = sc.sub_cat_id  
    JOIN hospitals  AS h ON h.hospital_id  = sc.main_hospital_id 
    JOIN products  AS p ON p.product_id   = s.product_id 
    JOIN product_group AS pg ON pg.id    = p.product_group_id 
    JOIN progress_steps AS ps ON sc.approval_step  = ps.step_id 
    WHERE s.approval_status='2' 
    AND sc.user_id='$mask5' 

的问题是，SC有3行S有6行。我需要返回所有六行，但目前它只返回3，其中每一行都对应于sc。根据该建议，我现在想

：

SELECT * FROM submissions AS s 
LEFT JOIN submission_category AS sc ON (s.submission_category = sc.sub_cat_id AND sc.user_id='$mask5') 
JOIN hospitals  AS h ON h.hospital_id  = sc.main_hospital_id 
JOIN products  AS p ON p.product_id   = s.product_id 
JOIN product_group AS pg ON pg.id    = p.product_group_id 
JOIN progress_steps AS ps ON sc.approval_step  = ps.step_id 
WHERE s.approval_status='2' 

但仍然得到三人行，不是6？在WHERELEFT JOINβed表格[秒]的

Answer 1

具有列“变为” LEFT JOIN成INNER（sc.user_id =“$ MASK5”总是返回NULL或假的情况下，有在submission_category没有相应的行）。将sc.user_id=...合并成合并条件：

.... 
LEFT JOIN submission_category AS sc ON (s.submission_category = sc.sub_cat_id AND 
sc.user_id='$mask5') 
...