TABLE T1
Name
ID
AMAN
10
JIM
11
SAM
12
TABLE T2
VAL
ID
A00
10
B0
11
The result I want:
T3
Name
ID
VAL
AMAN
10
A00
JIM
11
B0
SAM
12
NA
How can I write this query?
SELECT t1.name, t1.id, coalesce(t2.val,'n/a')
FROM t1
LEFT JOIN t2 ON t1.id = t2.id
You could left join on the id:
SELECT t1.name, t1.id, t2.val
FROM t1
LEFT JOIN t2 ON t1.id = t2.id
Try this
Select a.Name,
a.val,
b.val,
.
.
.
from TABLE T1 as a left join Table T2 b
on a.ID = b.ID
Related
Let's say I have Two tables T1 and T2 with ID as the column. For example
T1:ID
1
2
3
4
5
T2:ID
4
5
6
7
8
How can get a column where my result is 1 2 3 6 7 8 I want to exclude the common IDs from both the table and display the result in one column.
Hmmm . . . one method is union all:
select t1.id
from table1 t1
where not exists (select 1 from table2 t2 where t2.id = t1.id)
union all
select t1.id
from table2 t2
where not exists (select 1 from table1 t1 where t2.id = t1.id);
use minus
select id from
(
select id from t1
union
select id from t2
) a
minus select id from (
select id from t1 join t2 on t1.id=t2.id
) b
If your DBMS support FULL OUTER JOIN then i would do :
select coalesce(t1.id, t2.id)
from t1 full outer join
t2
on t2.id = t1.id
where (t1.id is null or t2.id is null);
I am trying to join two tables such that I am getting only a first match from the Right table instead of every match in Table2.
So if the query is:
SELECT T1.Name, T2.Dates
FROM Table1 T1
LEFT JOIN Table2 T2 ON T1.ID = T2 = ID
WHERE T1.Name = 'John'
I would like to see
John | 14/11/14
Joe | 10/10/2014
Jane | 25/10/2014
Instead of
John | 14/11/2014
John | 12/10/2014
Joe | 10/10/2014
Jane | 25/10/2014
Jane | 26/10/2014
Which join should I use?
You need to decide which row, you should select. Min or max as commented.
SELECT T1.Name,
( SELECT MIN( T2.Dates) FROM Table2 T2 WHERE T1.ID = T2 = ID) AS Dates
FROM Table1 T1
WHERE T1.Name = 'John'
The ANSI standard function row_number() can be a big help here. It is supported by most databases, so you can do:
SELECT T1.Name, T2.Dates
FROM Table1 T1 LEFT JOIN
(SELECT t2.*, ROW_NUMBER() OVER (PARTITION BY t2.ID ORDER BY t2.DATE DESC) as seqnum
FROM Table2 t2
) T2
ON T1.ID = T2.ID AND seqnum = 1
WHERE T1.Name = 'John';
In your question, you have only one column from the second table, so you can also do this with aggregation:
SELECT t1.ID, t1.Name, MAX(t2.Date)
FROM Table1 T1 LEFT JOIN
Table2 T2
ON t1.ID = t2.ID
WHERE T1.Name = 'John'
GROUP BY t1.ID, t1.Name;
Query
SELECT a.name,
MAX(b.Dates)
FROM tbl1 a
JOIN tbl2 b
ON a.id=b.id
WHERE a.name='John'
GROUP BY a.name;
Demo
I have two tables:
id
1
2
3
4
t1 AND t2
id | related_id
1 | 2
1 | 3
Where t2 is relationship table between t1 records. What is the best way to get desired output?
t1.id | t1_copy.id
1 | NULL -- want to get this NULL row
1 | 2
1 | 3
Simple JOIN would almost work, however it doesn't give me the first NULL row.
SELECT t1.id, t1_copy.id FROM t1
LEFT JOIN t2 ON t1.id = t2.id
LEFT JOIN t1 t1_copy ON t1_copy.id = t2.related_id
WHERE t1.id = 1
P.S: Yes, I do realize that desired output is wacky.
Seems like a simple UNION should do the trick
SELECT
id,
null as copy_id
FROM
t1
WHERE
exists (select * from t2 where t1.id = t2.id)
UNION ALL
SELECT
t1.id,
t2.related_id
FROM
t1
INNER JOIN t2
ON t1.id = t2.id
SQL Fiddle
SELECT DISTINCT t1.id, t1_copy.id FROM t1
LEFT OUTER JOIN t2 ON t1.id = t2.id
WHERE t1.id = 1
Please, help me with join results of commands (MS SQL):
SELECT name,value FROM table1 WHERE idfoo1 IN(SELECT _id FROM table3 where id = 1);
SELECT value FROM table2 WHERE idfoo2 IN(SELECT _id_2 FROM table3 where id = 1) AND name='fooname';
And I get:
name value
John 2
Bill 32
Alex 11
value
434
234
144
But I need join results.
name value value
John 2 434
Bill 32 234
Alex 11 144
So, id == id, _id != _id_2,
Use this query:
SELECT t1.name,
t1.value,
t2.value
FROM table1 t1
INNER JOIN table3 t3 ON t1.idfoo1 = t3._id
INNER JOIN table2 t2 ON t2.idfoo2 = t3._id_2
WHERE t3.id=1 AND t2.name = 'fooname'
Select a.name,a.value,c.value FROM table1 as a inner join table3 as b
on a.idfoo1=b.id and b.id=1 inner join table3 as c
on c.idfoo2=b._id_2 and b.id=1 and c.name='fooname'
i guess this is what you need-
SELECT t1.name, t1.value, t2.value
FROM table1 t1, table2 t2, table3 t3
WHERE
t1.idfoo1 = t3._id
AND t2.idfoo2 = t3._id_2
AND t3.id = 1
AND t2.name='fooname';
Say we have the following tables t1 and t2:
t1:
id | column_1
-------------
1 | 1
2 | 2
t2:
id | column_2
-------------
2 | 2
3 | 3
and we want to find the following result:
id | column_1 | column_2
------------------------
1 | 1 |
2 | 2 | 2
3 | | 3
This basically is the union of a right join with a left join. The following code works but feels clumsy:
(
SELECT t1.id, t1.column_1, t2.column_2
FROM t1
LEFT JOIN t2 ON t1.id = t2.id
)
UNION
(
SELECT t2.id, t1.column_1, t2.column_2
FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
)
Is there a better way to achieve this?
select a.id, t1.column_1, t2.column_2
from (
select id from t1
union
select id from t2
) a
left outer join t1 on a.id = t1.id
left outer join t2 on a.id = t2.id
Try this one:
SELECT t1.id, t1.column_1, t2.column_2
FROM t1
FULL OUTER JOIN t2 ON (t1.id = t2.id)
Edit: Doesn't work, MySQL does not know FULL OUTER JOIN.
Have a look here:
http://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql/
Haven't tried this myself, but this might work:
SELECT t1.id, t1.column_1, t2.column_2, t2a.column_2
FROM t1
LEFT JOIN t2 ON t1.id = t2.id
RIGHT JOIN t2 AS t2a ON t1.id = t2a.id