I have two tables which I need to use a where clause.
Table1
CustomerID Product
1 Car
2 Table
3 Golf
4 Foo
5 Yoo
Table2
CustomeID Comment
2 Three items
3 Returned
4 Complaint
I have a query which has two filters in the where statement like this
Select * from table1 a left
join table2 b on a.customerid= b.customerid
where b.comment<>'Returned' and b.comment not like 'Three%'
When I ran the query I just got one record. I want it to also return the two customerID's which are not in table2(three records)
SELECT * FROM Table1 A
LEFT JOIN Table2 B
ON A.CustomerID=B.CustomeID
WHERE ( B.COMMENT<>'RETURNED' AND B.COMMENT NOT LIKE 'THREE%')
OR B.CustomeID IS NULL
This should work I guess.
Try:
SELECT *
FROM table1 a
LEFT JOIN table2 b on a.customerid= b.customerid
WHERE (b.comment<>'Returned' and b.comment not like 'Three%')
OR (b.customerid is NULL)
I think you need to use LEFT OUTER JOIN:
Select * from table1 a left outer join table2 b on a.customerid = b.customerid where b.comment<>'Returned' and b.comment not like 'Three%'
I usually tend not to JOIN that much.
SELECT --It's a good practice to enumerate all rows you need, not just *.
T1.CUSTOMERID,
T1.PRODUCT
FROM
TABLE1 T1
WHERE
T1.CUSTOMERID NOT IN (
SELECT
T2.CUSTOMERID
FROM
TABLE2 T2
WHERE
T2.COMMENT !='Returned' AND
T2.COMMENT not like 'Three%')
How I can join this queries to single select (without temp table)?
SELECT t2.value,
t1.value
FROM table0 t1
INNER JOIN table1 t3 on t1.idrelation = t3.id and t3.idparent=#id
INNER JOIN table2 t2 on t2.idversion = t3.idchild and t2.name = 'FOO'
ORDER BY t1.value
SELECT SELECT COALESCE(t4._NAME+','+'')
FROM table1 t1
JOIN table1 t2 on t2.idparent = t1.idchild
JOIN table1 t3 on t3.idparent = t2.idchild
JOIN table3 t4 on t4._ID = t3.idchild
WHERE t1.idparent = #id
AND t4._TYPE ='TXT_CAT'
Something like this would help (once you can tell the columns on which you want to join):
select *
from
(
QUERY 1
) q1
join
(
QUERY 2
) q2
on q1.key1 = q2.key2
If you want to join them, there has to be common or uncommon ground.
Putting the 2 selects together is the easy part when you join the resultant sets, but unless you want all permutations of Ans1 and Ans2, then it is wise to determine some sort of where clause to allow it to be more effecient, and narrow it down for you.
If you give more table information, We could be able to adjust and give you something further, but that is the best we can do without taking arbitrary guesses as to what you are trying to accomplish here.
One thing i can part unto you:
Select A.name, B.id from (Select A.name, A.date from A) join (Select B.id, B.date from B) on A.date = B.date;
I have two tables, linked with an outer join. The relationship between the primary and secondary table is a 1 to [0..n]. The secondary table includes a timestamp column indicating when the record was added. I only want to retrieve the most recent record of the secondary table for each row in the primary. I have to use a group by on the primary table due to other tables also part of the SELECT. There's no way to use a 'having' clause though since this secondary table is not part of the group.
How can I do this without doing multiple queries?
For performance, try to touch the table least times
Option 1, OUTER APPLY
SELECT *
FROM
table1 a
OUTER APPY
(SELECT TOP 1 TimeStamp FROM table2 b
WHERE a.somekey = b.somekey ORDER BY TimeStamp DESC) x
Option 2, Aggregate
SELECT *
FROM
table1 a
LEFT JOIN
(SELECT MAX(TimeStamp) AS maxTs, somekey FROM table2
GROUP BY somekey) x ON a.somekey = x.somekey
Note: each table is mentioned once, no correlated subqueries
Something like:
SELECT a.id, b.*
FROM table1 a
INNER JOIN table2 b ON b.parentid = a.id
WHERE b.timestamp = (SELECT MAX(timestamp) FROM table2 c WHERE c.parentid = a.id)
Use LEFT JOIN instead of INNER JOIN if you want to show rows for IDs in table1 without any matches in table2.
select *
from table1 left outer join table2 a on
table1.id = a.table1_id
where
not exists (select 1 from table2 b where a.table1_id = b.table1_id and b.timestamp > a.timestamp)
The quickest way I know of is this:
SELECT
A.*,
B.SomeField
FROM
Table1 A
INNER JOIN (
SELECT
B1.A_ID,
B1.SomeField
FROM
Table2 B1
LEFT JOIN Table2 B2 ON (B1.A_ID=B2.A_ID) AND (B1.TimeStmp < B2.TimeStmp)
WHERE
B2.A_ID IS NULL
) B ON B.A_ID = A.ID
Is it possible to write a sql query where you know you have to use the left outer join..but cannot or are not allowed to use the "outer join" Key Word
I have two table sand want to get rows with null vaues from the left table ...this is pretty simple ...but am not supposed to use the key word....outer join....I need to right the logic for outer join myself
SELECT Field1
FROM table1
WHERE id NOT IN (SELECT id FROM table2)
SELECT Field1
FROM table1
WHERE NOT EXISTS (SELECT * FROM table2 where table2.id = table1.id)
This is something people do but it is deprecated and it does not currently work correctly (it sometimes will return a cross join instead of a left join) so it should NOT be used. I'm telling this only so you avoid using this solution.
SELECT Field1
FROM table1, table2 where table1.id *= table2.id
;WITH t1(c,d) AS
(
SELECT 1,'A' UNION ALL
SELECT 2,'B'
),t2(c,e) AS
(
SELECT 1,'C' UNION ALL
SELECT 1,'D' UNION ALL
SELECT 3,'E'
)
SELECT t1.c, t1.d, t2.c, t2.e
FROM t1, t2
WHERE t1.c = t2.c
UNION ALL
SELECT t1.c, t1.d, NULL, NULL
FROM t1
WHERE c NOT IN (SELECT c
FROM t2
WHERE c IS NOT NULL)
Returns
c d c e
----------- ---- ----------- ----
1 A 1 C
1 A 1 D
2 B NULL NULL
(Equivalent to)
SELECT t1.c, t1.d, t2.c, t2.e
FROM t1
LEFT JOIN t2
ON t1.c = t2.c
For SQL Server, you can just use LEFT JOIN - the OUTER is optional, just like INTO in an INSERT statement.
This is the same for all OUTER JOINs.
For an INNER JOIN you can just specify JOIN with no qualifiers and it is interpreted as an INNER JOIN.
This will give you all the rows in table A that don't have a matching row in table B:
SELECT *
FROM A
WHERE NOT EXISTS (
SELECT 1
FROM B
WHERE A.id = B.id
);
Returns all the matching rows from both tables:
SELECT a.*,b.* FROM table_a a, table_b b
WHERE a.key_field = b.key_field
Potential drawback is non-matches will be skipped.
I want to do a full outer join in MySQL. Is this possible? Is a full outer join supported by MySQL?
You don't have full joins in MySQL, but you can sure emulate them.
For a code sample transcribed from this Stack Overflow question you have:
With two tables t1, t2:
SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
The query above works for special cases where a full outer join operation would not produce any duplicate rows. The query above depends on the UNION set operator to remove duplicate rows introduced by the query pattern. We can avoid introducing duplicate rows by using an anti-join pattern for the second query, and then use a UNION ALL set operator to combine the two sets. In the more general case, where a full outer join would return duplicate rows, we can do this:
SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION ALL
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
WHERE t1.id IS NULL
The answer that Pablo Santa Cruz gave is correct; however, in case anybody stumbled on this page and wants more clarification, here is a detailed breakdown.
Example Tables
Suppose we have the following tables:
-- t1
id name
1 Tim
2 Marta
-- t2
id name
1 Tim
3 Katarina
Inner Joins
An inner join, like this:
SELECT *
FROM `t1`
INNER JOIN `t2` ON `t1`.`id` = `t2`.`id`;
Would get us only records that appear in both tables, like this:
1 Tim 1 Tim
Inner joins don't have a direction (like left or right) because they are explicitly bidirectional - we require a match on both sides.
Outer Joins
Outer joins, on the other hand, are for finding records that may not have a match in the other table. As such, you have to specify which side of the join is allowed to have a missing record.
LEFT JOIN and RIGHT JOIN are shorthand for LEFT OUTER JOIN and RIGHT OUTER JOIN; I will use their full names below to reinforce the concept of outer joins vs inner joins.
Left Outer Join
A left outer join, like this:
SELECT *
FROM `t1`
LEFT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`;
...would get us all the records from the left table regardless of whether or not they have a match in the right table, like this:
1 Tim 1 Tim
2 Marta NULL NULL
Right Outer Join
A right outer join, like this:
SELECT *
FROM `t1`
RIGHT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`;
...would get us all the records from the right table regardless of whether or not they have a match in the left table, like this:
1 Tim 1 Tim
NULL NULL 3 Katarina
Full Outer Join
A full outer join would give us all records from both tables, whether or not they have a match in the other table, with NULLs on both sides where there is no match. The result would look like this:
1 Tim 1 Tim
2 Marta NULL NULL
NULL NULL 3 Katarina
However, as Pablo Santa Cruz pointed out, MySQL doesn't support this. We can emulate it by doing a UNION of a left join and a right join, like this:
SELECT *
FROM `t1`
LEFT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`
UNION
SELECT *
FROM `t1`
RIGHT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`;
You can think of a UNION as meaning "run both of these queries, then stack the results on top of each other"; some of the rows will come from the first query and some from the second.
It should be noted that a UNION in MySQL will eliminate exact duplicates: Tim would appear in both of the queries here, but the result of the UNION only lists him once. My database guru colleague feels that this behavior should not be relied upon. So to be more explicit about it, we could add a WHERE clause to the second query:
SELECT *
FROM `t1`
LEFT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`
UNION
SELECT *
FROM `t1`
RIGHT OUTER JOIN `t2` ON `t1`.`id` = `t2`.`id`
WHERE `t1`.`id` IS NULL;
On the other hand, if you wanted to see duplicates for some reason, you could use UNION ALL.
Using a union query will remove duplicates, and this is different than the behavior of full outer join that never removes any duplicates:
[Table: t1] [Table: t2]
value value
----------- -------
1 1
2 2
4 2
4 5
This is the expected result of a full outer join:
value | value
------+-------
1 | 1
2 | 2
2 | 2
Null | 5
4 | Null
4 | Null
This is the result of using left and right join with union:
value | value
------+-------
Null | 5
1 | 1
2 | 2
4 | Null
SQL Fiddle
My suggested query is:
select
t1.value, t2.value
from t1
left outer join t2
on t1.value = t2.value
union all -- Using `union all` instead of `union`
select
t1.value, t2.value
from t2
left outer join t1
on t1.value = t2.value
where
t1.value IS NULL
The result of the above query that is as the same as the expected result:
value | value
------+-------
1 | 1
2 | 2
2 | 2
4 | NULL
4 | NULL
NULL | 5
SQL Fiddle
#Steve Chambers: [From comments, with many thanks!]
Note: This may be the best solution, both for efficiency and for generating the same results as a FULL OUTER JOIN. This blog post also explains it well - to quote from Method 2: "This handles duplicate rows correctly and doesn’t include anything it shouldn’t. It’s necessary to use UNION ALL instead of plain UNION, which would eliminate the duplicates I want to keep. This may be significantly more efficient on large result sets, since there’s no need to sort and remove duplicates."
I decided to add another solution that comes from full outer join visualization and math. It is not better than the above, but it is more readable:
Full outer join means (t1 ∪ t2): all in t1 or in t2
(t1 ∪ t2) = (t1 ∩ t2) + t1_only + t2_only: all in both t1 and t2 plus all in t1 that aren't in t2 and plus all in t2 that aren't in t1:
-- (t1 ∩ t2): all in both t1 and t2
select t1.value, t2.value
from t1 join t2 on t1.value = t2.value
union all -- And plus
-- all in t1 that not exists in t2
select t1.value, null
from t1
where not exists( select 1 from t2 where t2.value = t1.value)
union all -- and plus
-- all in t2 that not exists in t1
select null, t2.value
from t2
where not exists( select 1 from t1 where t2.value = t1.value)
SQL Fiddle
None of the previous answers are actually correct, because they do not follow the semantics when there are duplicated values.
For a query such as (from this duplicate):
SELECT * FROM t1 FULL OUTER JOIN t2 ON t1.Name = t2.Name;
The correct equivalent is:
SELECT t1.*, t2.*
FROM (SELECT name FROM t1 UNION -- This is intentionally UNION to remove duplicates
SELECT name FROM t2
) n LEFT JOIN
t1
ON t1.name = n.name LEFT JOIN
t2
ON t2.name = n.name;
If you need this to work with NULL values (which may also be necessary), then use the NULL-safe comparison operator, <=> rather than =.
MySQL does not have FULL-OUTER-JOIN syntax. You have to emulate it by doing both LEFT JOIN and RIGHT JOIN as follows:
SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
But MySQL also does not have a RIGHT JOIN syntax. According to MySQL's outer join simplification, the right join is converted to the equivalent left join by switching the t1 and t2 in the FROM and ON clause in the query. Thus, the MySQL query optimizer translates the original query into the following -
SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT * FROM t2
LEFT JOIN t1 ON t2.id = t1.id
Now, there is no harm in writing the original query as is, but say if you have predicates like the WHERE clause, which is a before-join predicate or an AND predicate on the ON clause, which is a during-join predicate, then you might want to take a look at the devil; which is in details.
The MySQL query optimizer routinely checks the predicates if they are null-rejected.
Now, if you have done the RIGHT JOIN, but with WHERE predicate on the column from t1, then you might be at a risk of running into a null-rejected scenario.
For example, the query
SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
WHERE t1.col1 = 'someValue'
UNION
SELECT * FROM t1
RIGHT JOIN t2 ON t1.id = t2.id
WHERE t1.col1 = 'someValue'
gets translated to the following by the query optimizer:
SELECT * FROM t1
LEFT JOIN t2 ON t1.id = t2.id
WHERE t1.col1 = 'someValue'
UNION
SELECT * FROM t2
LEFT JOIN t1 ON t2.id = t1.id
WHERE t1.col1 = 'someValue'
So the order of tables has changed, but the predicate is still applied to t1, but t1 is now in the 'ON' clause. If t1.col1 is defined as NOT NULL
column, then this query will be null-rejected.
Any outer-join (left, right, full) that is null-rejected is converted to an inner-join by MySQL.
Thus the results you might be expecting might be completely different from what the MySQL is returning. You might think its a bug with MySQL's RIGHT JOIN, but that’s not right. Its just how the MySQL query optimizer works. So the developer in charge has to pay attention to these nuances when he/she is constructing the query.
I modified shA.t's query for more clarity:
-- t1 left join t2
SELECT t1.value, t2.value
FROM t1 LEFT JOIN t2 ON t1.value = t2.value
UNION ALL -- include duplicates
-- t1 right exclude join t2 (records found only in t2)
SELECT t1.value, t2.value
FROM t1 RIGHT JOIN t2 ON t1.value = t2.value
WHERE t1.value IS NULL
In SQLite you should do this:
SELECT *
FROM leftTable lt
LEFT JOIN rightTable rt ON lt.id = rt.lrid
UNION
SELECT lt.*, rl.* -- To match column set
FROM rightTable rt
LEFT JOIN leftTable lt ON lt.id = rt.lrid
You can do the following:
(SELECT
*
FROM
table1 t1
LEFT JOIN
table2 t2 ON t1.id = t2.id
WHERE
t2.id IS NULL)
UNION ALL
(SELECT
*
FROM
table1 t1
RIGHT JOIN
table2 t2 ON t1.id = t2.id
WHERE
t1.id IS NULL);
You can just convert a full outer join, e.g.
SELECT fields
FROM firsttable
FULL OUTER JOIN secondtable ON joincondition
into:
SELECT fields
FROM firsttable
LEFT JOIN secondtable ON joincondition
UNION ALL
SELECT fields (replacing any fields from firsttable with NULL)
FROM secondtable
WHERE NOT EXISTS (SELECT 1 FROM firsttable WHERE joincondition)
Or if you have at least one column, say foo, in firsttable that is NOT NULL, you can do:
SELECT fields
FROM firsttable
LEFT JOIN secondtable ON joincondition
UNION ALL
SELECT fields
FROM firsttable
RIGHT JOIN secondtable ON joincondition
WHERE firsttable.foo IS NULL
SELECT
a.name,
b.title
FROM
author AS a
LEFT JOIN
book AS b
ON a.id = b.author_id
UNION
SELECT
a.name,
b.title
FROM
author AS a
RIGHT JOIN
book AS b
ON a.id = b.author_id
I fix the response, and works include all rows (based on the response of Pavle Lekic):
(
SELECT a.* FROM tablea a
LEFT JOIN tableb b ON a.`key` = b.key
WHERE b.`key` is null
)
UNION ALL
(
SELECT a.* FROM tablea a
LEFT JOIN tableb b ON a.`key` = b.key
where a.`key` = b.`key`
)
UNION ALL
(
SELECT b.* FROM tablea a
right JOIN tableb b ON b.`key` = a.key
WHERE a.`key` is null
);
Use:
SELECT * FROM t1 FULL OUTER JOIN t2 ON t1.id = t2.id;
It can be recreated as follows:
SELECT t1.*, t2.*
FROM (SELECT * FROM t1 UNION SELECT name FROM t2) tmp
LEFT JOIN t1 ON t1.id = tmp.id
LEFT JOIN t2 ON t2.id = tmp.id;
Using a UNION or UNION ALL answer does not cover the edge case where the base tables have duplicated entries.
Explanation:
There is an edge case that a UNION or UNION ALL cannot cover. We cannot test this on MySQL as it doesn't support full outer joins, but we can illustrate this on a database that does support it:
WITH cte_t1 AS
(
SELECT 1 AS id1
UNION ALL SELECT 2
UNION ALL SELECT 5
UNION ALL SELECT 6
UNION ALL SELECT 6
),
cte_t2 AS
(
SELECT 3 AS id2
UNION ALL SELECT 4
UNION ALL SELECT 5
UNION ALL SELECT 6
UNION ALL SELECT 6
)
SELECT * FROM cte_t1 t1 FULL OUTER JOIN cte_t2 t2 ON t1.id1 = t2.id2;
This gives us this answer:
id1 id2
1 NULL
2 NULL
NULL 3
NULL 4
5 5
6 6
6 6
6 6
6 6
The UNION solution:
SELECT * FROM cte_t1 t1 LEFT OUTER JOIN cte_t2 t2 ON t1.id1 = t2.id2
UNION
SELECT * FROM cte_t1 t1 RIGHT OUTER JOIN cte_t2 t2 ON t1.id1 = t2.id2
Gives an incorrect answer:
id1 id2
NULL 3
NULL 4
1 NULL
2 NULL
5 5
6 6
The UNION ALL solution:
SELECT * FROM cte_t1 t1 LEFT OUTER join cte_t2 t2 ON t1.id1 = t2.id2
UNION ALL
SELECT * FROM cte_t1 t1 RIGHT OUTER JOIN cte_t2 t2 ON t1.id1 = t2.id2
Is also incorrect.
id1 id2
1 NULL
2 NULL
5 5
6 6
6 6
6 6
6 6
NULL 3
NULL 4
5 5
6 6
6 6
6 6
6 6
Whereas this query:
SELECT t1.*, t2.*
FROM (SELECT * FROM t1 UNION SELECT name FROM t2) tmp
LEFT JOIN t1 ON t1.id = tmp.id
LEFT JOIN t2 ON t2.id = tmp.id;
Gives the following:
id1 id2
1 NULL
2 NULL
NULL 3
NULL 4
5 5
6 6
6 6
6 6
6 6
The order is different, but otherwise matches the correct answer.
Use a cross join solution:
SELECT t1.*, t2.*
FROM table1 t1
INNER JOIN table2 t2
ON 1=1;
It is also possible, but you have to mention the same field names in select.
SELECT t1.name, t2.name FROM t1
LEFT JOIN t2 ON t1.id = t2.id
UNION
SELECT t1.name, t2.name FROM t2
LEFT JOIN t1 ON t1.id = t2.id
The SQL standard says full join on is inner join on rows union all unmatched left table rows extended by nulls union all right table rows extended by nulls. Ie inner join on rows union all rows in left join on but not inner join on union all rows in right join on but not inner join on.
Ie left join on rows union all right join on rows not in inner join on. Or if you know your inner join on result can't have null in a particular right table column then "right join on rows not in inner join on" are rows in right join on with the on condition extended by and that column is null.
Ie similarly right join on union all appropriate left join on rows.
From What is the difference between “INNER JOIN” and “OUTER JOIN”?:
(SQL Standard 2006 SQL/Foundation 7.7 Syntax Rules 1, General Rules 1 b, 3 c & d, 5 b.)