I have base table with 1000 values. and second temporary table with 100 values. I need to compare them by guids and return only those rows from second table that do not exist in first table. I need the fastest performance solution for that. Thanks!
The classic left join/isnull test
select A.*
from secondTbl A
left join firstTbl B on A.guid = B.guid
WHERE B.guid is null
SELECT * FROM Table2 WHERE
NOT EXISTS (SELECT 'x' FROM table1 where
table1.field= table2.field)
http://weblogs.sqlteam.com/mladenp/archive/2007/05/18/60210.aspx
Related
I face issue about duplicate data when join table, here my sample data table I have
-- Table A
I want to join with
-- Table B
this my query notation for join both table,
select a.trans_id, name
from tableA a
inner join tableB b
on a.ID_Trans = b.trans_id
and this the result, why I get the duplicating data which should show only two lines of data, please help me to solve this case.
Firstly, as you have been told multiple times in the comments, this is working exactly as you have written, and (more importantly) as intended. You have 2 rows in tableA and those 2 rows match 2 rows in your table tableB according to the ON clause. This means that each join operation, for the each of the rows in tableA, results in 2 rows as well; thus 4 rows (2 * 2 = 4).
Considering that your table, TableA only has one column then it seems that you should be cleaning up that data and deleting the duplicates. There are plenty of examples on how to do that already (example).
Perhaps the column you show us in TableA is one many, and thus instead you have a denormalisation issue, and instead there should be another table with the details of Id_trans and a PRIMARY KEY or UNIQUE CONSTRAINT/INDEX on it. Then you would join fron that table to TableB.
Finally, what you might be after is an EXISTS, which would look like this:
SELECT B.trans_id, B.[name]
FROM dbo.TableB B
WHERE EXISTS(SELECT 1
FROM dbo.TableA A
WHERE A.ID_Trans = B.trans_id); --Odd that it's called ID_Trans in one table, and Trans_ID in another
As the comments mentioned your query does exactly what you asked it to do but I think you wanted something like:
select a.trans_id, a.name, b.name
from tableA a
inner join tableB b on a.trans_id = b.trans_id
group by a.trans_id, a.name, b.name
Since there are two rows in both table with same ID join will make them four. You can use distinct to remove duplicates:
select distinct a.trans_id, name
from tableA a
inner join tableB b
on a.id_trans = b.trans_id
But I would suggest to use exists:
select trans_id, name
from tableB b
exists (select 1 from tableA a where a.trans_id=b.trans_id)
I am very new to vertica db and hence looking for different efficient ways for comparing two tables of average size 500ml-800ml rows in vertica. I have a process that gets the data from vertica view and dump in to SQL server for later merge to final table in sql server. for few large tables combine it is dumping about 3bl rows daily. Instead of dumping all data I want to take daily snapshot, and compare it with previous days snapshot on vertica side only and then push changed rows only in to SQL SEREVER.
lets say previous snapshot is stored in tableA, today's snapshot stored in tableB. PK on both table is column named OrderId.
Simplest way I can think of is
Select * from tableB
Where OrderId NOT IN (
SELECT * from tableA
INTERSECT
SELECT * from tbleB
)
So my questions are:
Is there any other/better option in vertica to get only changed rows between two tables? Or should I
even consider doing this compare on vertica side?
How much doing such comparison should take?
What should I consider to improve the performance of such query?
If your columns have no NULL values, then a massive LEFT JOIN would seem to do what you want:
select b.*
from tableB b left join
tableA a
on b.OrderId = a.OrderId and
b.col1 = a.col1 and
. . . -- for all the columns you care about
However, I think you want except:
select b.*
from tableB b
except
select a.*
from tableA a;
I imagine this would have reasonable performance.
Do you have a primary key in the two tables?
Then my technique, for a complete Change Data Capture, is:
SELECT
'I' AS to_do
, newrows.*
FROM tb_today newrows
LEFT
JOIN tb_yesterday oldrows USING(id)
WHERE oldrows.id IS NULL
UNION ALL
SELECT
'U' AS to_do
, newrows.*
FROM tb_today newrows
JOIN tb_yesterday oldrows
WHERE oldrows.fname <> newrows.fname
OR oldrows.lnamd <> newrows.lname
OR oldrows.bdate <> newrwos.bdate
OR oldrows.sal <> newrows.sal
[...]
OR oldrows.lastcol <> newrows.lastcol
UNION ALL
SELECT
'D' AS to_do
, oldrows.*
FROM tb_yesterday oldrows
LEFT
JOIN tb_today oldrows USING(id)
WHERE newrows.id IS NULL
;
Just leave out the last leg of the UNION SELECT if you don't want to cater for DELETEs ('D')
Good luck
you also do it nicely using joins:
SELECT b.*
FROM tableB AS b
LEFT JOIN tableA AS a ON a.id = b.id
WHERE a.id IS NULL
so above query return only diff from TableB to TableA i.e. data which is present in both table will be skipped...
I have a scenario like this, there are 2 tables table_1 and table_2. Both table have a common column called column_1(no foreign_Key constraints!!). Table_1 can have some extra rows which are not present in table_2(In other words, table_2 is a sub-set of table_1). I want to list all those items which are only present in table_1 but not in table_2.
Kindly help in writing the sql query for the same.
Thanks in advance.
SELECT a.*
FROM table1 a
LEFT JOIN table2 b
on a.column_1 = b.column_1
WHERE b.column_1 IS NULL
if those two tables are not related with each other, better add an index on table1.column_1 and table2.column_1 so that it won't require full table scan (which slows the performance)
select * from table1
inner join table2 on table1.column1=table2.column1
select a.* from table1 a left outer join table2 b on a.col1=b.col1;
I'm a newbie, just learning SQL and have this question: I have two tables with the same columns. Some registers are in the two tables but others only are in one of the tables. To illustrate, suppose table A = (1,2,3,4), table B=(3,4,5,6), numbers are registers. I need to select all registers in table B if they are not in table A, that is result=(5,6). What query should I use? Maybe a join. Thanks.
You can either use a NOT IN query like this:
SELECT col from A where col not in (select col from B)
or use an outer join:
select A.col
from A LEFT OUTER JOIN B on A.col=B.col
where B.col is NULL
The first is easier to understand, but the second is easier to use with more tables in the query.
Select register from TABLE_B b
Where not exists (Select register from TABLE_A a where a.register = b.register)
I assumed you have a column named register in TABLE_A and TABLE_B
I have two tables and I need to remove rows from the first table if an exact copy of a row exists in the second table.
Does anyone have an example of how I would go about doing this in MSSQL server?
Well, at some point you're going to have to check all the columns - might as well get joining...
DELETE a
FROM a -- first table
INNER JOIN b -- second table
ON b.ID = a.ID
AND b.Name = a.Name
AND b.Foo = a.Foo
AND b.Bar = a.Bar
That should do it... there is also CHECKSUM(*), but this only helps - you'd still need to check the actual values to preclude hash-conflicts.
If you're using SQL Server 2005, you can use intersect:
delete * from table1 intersect select * from table2
I think the psuedocode below would do it..
DELETE FirstTable, SecondTable
FROM FirstTable
FULL OUTER JOIN SecondTable
ON FirstTable.Field1 = SecondTable.Field1
... continue for all fields
WHERE FirstTable.Field1 IS NOT NULL
AND SecondTable.Field1 IS NOT NULL
Chris's INTERSECT post is far more elegant though and I'll use that in future instead of writing out all of the outer join criteria :)
I would try a DISTINCT query and do a union of the two tables.
You can use a scripting language like asp/php to format the output into a series of insert statements to rebuild the table the resulting unique data.
try this:
DELETE t1 FROM t1 INNER JOIN t2 ON t1.name = t2.name WHERE t1.id = t2.id