Databases
StackOverflow2013
Postsdbo
POHow to return null values using SQL Left Join
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow to return null values using SQL Left Join
    primarykey
    data
    text
    <p>Please look at this SQL Fiddle for the tables and what query I have tried:<br> <a href="http://sqlfiddle.com/#!2/4c7b2/1" rel="noreferrer">SQL Fiddle</a> </p> <p>So basically, I have two tables namely <strong>tbl_curriculum</strong> and <strong>tbl_enrolled_subjects</strong>. </p> <p><strong>tbl_curriculum</strong> contains all the subjects (subject_id) a student should take based on his course (course_id).<br> <strong>tbl_enrolled_subjects</strong> contains all the subjects the student has taken/enrolled based on <strong>tbl_curriculum</strong>. </p> <p>I want to check which subjects the student has taken and which is not, the query should return something like this: </p> <pre><code>Subject_id|Grade|Status 23 | 2 |Passed 24 | 2 |Passed 31 | 2 |Passed 50 | 2 |Passed 83 | 1 |Passed 27 |NULL |NULL 28 |NULL |NULL 29 |NULL |NULL </code></pre> <p>. . . And So On.</p> <p>Subject_ID with Grade and Status mean the student has already taken the subject. On the otherhand, NULL values indicates the the student has not taken those subjects yet.<br> I used this query: </p> <pre><code>SELECT a.subject_id, b.grade, b.status FROM tbl_curriculum a LEFT JOIN tbl_enrolled_subjects b ON a.course_id = b.course_id AND a.subject_id = b.subject_id WHERE b.student_id_no='05-0531'; </code></pre> <p>But I keep getting only the subjects the student has taken.</p> <pre><code>Subject_id|Grade|Status 23 | 2 |Passed 24 | 2 |Passed 31 | 2 |Passed 50 | 2 |Passed 83 | 1 |Passed </code></pre> <p>Am I missing something? Thanks in advance.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USRuben_PH
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow to return null values using SQL Left Join
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POHow to return null values using SQL Left Join
      1. This table or related slice is empty.
      1. VTUpMod
    1. COyou can't, the where clause need to be evaluated as true
      singulars
      1. POHow to return null values using SQL Left Join
      1. USajreal
    2. CO@ajreal What should I do then?
      singulars
      1. POHow to return null values using SQL Left Join
      1. USRuben_PH
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload