MySQL Join Return Null

Question

I have two tables

Table_1
id|subject_code|subject_id
 1|Test1       |1
 2|Test2       |2
 3|Test3       |3

Table2
id|subject_id|grade|status
 1|1         |5.00 |Fail
 2|3         |2.25 |Pass

Now, I want to create a query that will return the following,

Table3
subject_code|grade|status
Test1       |5.00 |Fail
Test2       |NULL |NULL
Test3       |2.25 |Pass

I have read about combining left join and union all but I am lost on how to do that. Thanks in advance.

Sashi Kant · Accepted Answer · 2012-12-04T09:42:35.243

4

Try a left join, like this::

Select 
DISTINCT(table1.subject_code), 
grade, 
status

from table1 
LEFT join table2 on (table1.subject_id=table2.subject_id)

edited Dec 04 '12 at 09:42

answered Dec 04 '12 at 09:18

Sashi Kant

13,277
9
44
71

This returns identical rows. – Ruben_PH Dec 04 '12 at 09:35

score 4 · Answer 2 · edited Dec 04 '12 at 09:35

4

SELECT subject_code, grade, status 
FROM Table_1 t1 
LEFT JOIN Table2 t2 ON t1.subject_id = t2.subject_id;

edited Dec 04 '12 at 09:35

Mahmoud Gamal

78,257
17
139
164

answered Dec 04 '12 at 09:19

Stanley

5,057
4
34
44

This returns identical rows. – Ruben_PH Dec 04 '12 at 09:34

score 1 · Answer 3 · answered Dec 04 '12 at 09:20

1

I suppose a simple LEFT JOIN would do the trick :

SELECT Table_1.subject_code, Table2.grade, Table2.status FROM Table_1 LEFT JOIN Table2 ON Table2.subject_id = Table_1.subject_id;

answered Dec 04 '12 at 09:20

Eric MORAND

6,373
4
27
34

This returns identical rows. – Ruben_PH Dec 04 '12 at 09:29

MySQL Join Return Null

3 Answers3