I have two tables in SQL Server 2012 , that Many to Many (n to m) relationship established between them:
table1 and table2
I need to have a View or Query (or SP) from table2 that will show the following result:
Is it possible to write this query?
SELECT a.RowID, b.Table1_Id, a.Price
FROM table2 a
INNER JOIN table1 b
ON a.Table1_Id=b.Table1_ID
Related
So i'm trying to convert a SQL delete query to Hive one. Im using hive .12 version's which doesn't supports delete.
Below is the SQL query:
Delete from t1 c where exists(select 1 from t2 a where
a.emplid=c.employee_id and a.project_status='test')
Now i tried tried using NOT IN for the above query but due to some reasons we cannot use NOT IN in our queries.
below is Hive query i have written but i'm not sure as its not giving correct results. i'm pretty new to hive. can anyone help on this.
INSERT Overwrite table t1
select * from t1 c left outer join t2 a on (c.employee_id=a.employee_id)
where a.project_status= 'test'
and a.employee_id is null
Move project_status='test' condition to the subquery or into the on clause. Also you should select columns only from table c.
Example with filter in the subquery:
insert overwrite table t1
select c.*
from t1 c
left join (select employee_id
from t2
where project_status='test'
) a on (c.employee_id=a.employee_id)
where a.employee_id is null;
Example with additional condition in the ON:
insert overwrite table t1
select c.*
from t1 c
left join t2 a on (c.employee_id=a.employee_id and a.project_status='test')
where a.employee_id is null;
Is there any difference between these two statements:
-- Statement 1:
SELECT *
FROM Table1 t1
LEFT OUTER JOIN TABLE2 t2 on t1.id = t2.id
and
-- Statement 2:
SELECT *
FROM Table1 t1
LEFT OUTER JOIN (SELECT id, a, b, c FROM Table2) t2 on t1.id = t2.id
I'm not an expert but statement 2 just looks like poorly written sql, and like it would take much longer. I'm attempting to optimize a code block and it has many joins like the second one. Are they technically the same and I can just replace with the standard join statement 1?
Thanks!
Ps. This is Oracle, and working with 100's of millions of rows.
PSS. I'm doing my own detective work to figure out if they are the same, and time differences, was hoping an expert could explain if there is a technical difference what it is.
They are not same queries, with the lack of a criteria in the subquery that depends on whether the all columns and all column names of the TABLE2 is involved in the subquery. If the subquery involves all of the column names of the TABLE2 in the select list then they are the same query and the subquery is unnecessary. With subquery I refer to the part with a select statement after the join statement in the parens.
The first one uses the TABLE2 with its all columns, all those columns will be available in the result set where the criteria met.
However in the second one the table you make the JOIN is not the TABLE2 of yours but a table with just columns from TABLE2 specified in the subquery's SELECT list, namely id, a, b, and c. But it will have all the rows after this subquery since no criteria is enforced on it by a WHERE clause in the subquery.
You will have same number of rows with only selected columns participating from the TABLE2.
The second one is not necessarily the poorly written one. You could have a criteria to met before you JOIN to the TABLE2.
I want to do following:
INSERT INTO Table0(value1, value2)
SELECT
(SELECT t1.something1 FROM Table1 t1 WHERE t1.id = :t1id),
(SELECT max(t2.something2) FROM Table2 t2 WHERE t2.some = :t2Some)
FROM Table1, Table2
But hibernate complains that I want to insert entity (Table1) as string (value1). It looks like subqueries in HQL returns entities instead of column values. Can I force it not to do so?
I know, that I can do like:
INSERT INTO Table0(value1, value2)
SELECT t1.something1, max(t2.something2) FROM Table1 t1, Table2 t2 WHERE ...
but it generates bad SQL for Oracle, because there is HIBERNATE_SEQUENCE.NEXTVAL in SELECT and Oracle does not allow to do so.
It looks like first query works now, maybe it was about Hibernate version.
I have two tables
Table A has columns id|name|age.
Table B has columns id|name|age.
Sample Records from table A
1|xavi |23
2|christine|24
3|faisal |25
5|jude |27
Sample Records from table B
1|xavi |23
2|christine|22
3|faisal |23
4|ram |25
If id values from table A matches in table B than take records from table A only.
Also take records which are present in table A only
Also take records which are present in table B only
So my result should be
1|xavi |23
2|christine|24
3|faisal |25
4|ram |25
5|jude |27
You can simply use union operator to get unique values from both tables. Operator UNION will remove repeated values.
SELECT * FROM tableA AS t1
UNION
SELECT * FROM tableB AS t2
You have a precedence problem here. Take all the records from table A and then the extra records from table B:
select *
from A
union all
select *
from B
where B.id not in (select A.id from A);
You can also express this with a full outer join (assuming id is not duplicated in either table):
select coalesce(A.id, B.id) as id,
coalesce(A.name, B.name) as name,
coalesce(A.age, B.age) as age
from A full outer join
B
on A.id = B.id;
In this case, the coalesce() gives priority to the values in A.
select distinct * FROM
(
select ID, NAME, AGE from TableA
UNION ALL
select ID, NAME, AGE from TableB
) TableAB
Some things to consider --> Unless you're updating specific tables and the records are the same, it will not matter which table you're viewing the records from (because they're the same...).
If you want to see which table the records are deriving from, let me know and i'll show you how to do that as well... but the query is more complex and i don't really think it's required for the purpose described above. let me know if this helps... thanks, Brian
If the tables has relation you need:
Select DISTINCT *
from tableA a
Inner Join tableB b
On a.id = b.id
If not:
You have to use UNION and after using DISTINCT.
DISTINCT will not permit repeat rows.
Say you've got the following query on 9i:
SELECT /*+ USE_HASH(t2 t3) */
* FROM
table1 t1 -- this has lots of rows
LEFT JOIN table2 t2 ON t1.col1 = t2.col1
AND t1.col2 = t2.col2
LEFT JOIN table3 t3 ON t1.col1 = t3.col1
AND t1.col2 = t3.col2
Due to 9i not having RIGHT OUTER HASH JOIN, it needs to hash table1 for both joins. Does it re-hash table1 between joining t2 and t3 (even though it's using the same join columns), or does it keep the same hash information for both joins?
It would need to rehash since the second hash would be table3 against the join of table1/table2 rather than against table1. Or vice versa.
For example, say TABLE1 had 100 rows, table2 had 50 and table3 had 10.
Joining table1 to table2 may give 500 rows. It then joins that result set to table3 to give (perhaps) 700 rows.
It won't do a join of table1 to table2, then a join of table1 to table3, then a join of those two intermediate results.
Look at the plan, it'll tell you the answer.
An example might be something like (I've just made this up):
SELECT
HASH JOIN
HASH JOIN
TABLE FULL SCAN table1
TABLE FULL SCAN table2
TABLE FULL SCAN table3
This sample plan involves a scan through table1, hashing its contents as it goes; scans through table2, hashes the results of the join into a second hash, then finally scans table3.
There are other plans it could choose from.
If table1 is the biggest table, and the optimizer knows this (due to stats), it probably won't drive from it though.