I need to create a background job that processes a table looking for rows matching on a particular id with different statuses. It will store the row data in a string to compare the data against a row with a matching id.
I know the syntax to get the row data, but I have never tried comparing 2 rows from the same table before. How is it done? Would I need to use variables to store the data from each? Or some other way?
(Using SQL Server 2008)
You can join a table to itself as many times as you require, it is called a self join.
An alias is assigned to each instance of the table (as in the example below) to differentiate one from another.
SELECT a.SelfJoinTableID
FROM dbo.SelfJoinTable a
INNER JOIN dbo.SelfJoinTable b
ON a.SelfJoinTableID = b.SelfJoinTableID
INNER JOIN dbo.SelfJoinTable c
ON a.SelfJoinTableID = c.SelfJoinTableID
WHERE a.Status = 'Status to filter a'
AND b.Status = 'Status to filter b'
AND c.Status = 'Status to filter c'
OK, after 2 years it's finally time to correct the syntax:
SELECT t1.value, t2.value
FROM MyTable t1
JOIN MyTable t2
ON t1.id = t2.id
WHERE t1.id = #id
AND t1.status = #status1
AND t2.status = #status2
Some people find the following alternative syntax easier to see what is going on:
select t1.value,t2.value
from MyTable t1
inner join MyTable t2 on
t1.id = t2.id
where t1.id = #id
SELECT COUNT(*) FROM (SELECT * FROM tbl WHERE id=1 UNION SELECT * FROM tbl WHERE id=2) a
If you got two rows, they different, if one - the same.
SELECT * FROM A AS b INNER JOIN A AS c ON b.a = c.a
WHERE b.a = 'some column value'
I had a situation where I needed to compare each row of a table with the next row to it, (next here is relative to my problem specification) in the example next row is specified using the order by clause inside the row_number() function.
so I wrote this:
DECLARE #T TABLE (col1 nvarchar(50));
insert into #T VALUES ('A'),('B'),('C'),('D'),('E')
select I1.col1 Instance_One_Col, I2.col1 Instance_Two_Col from (
select col1,row_number() over (order by col1) as row_num
FROM #T
) AS I1
left join (
select col1,row_number() over (order by col1) as row_num
FROM #T
) AS I2 on I1.row_num = I2.row_num - 1
after that I can compare each row to the next one as I need
Related
I have a table with 3 values.
ID AuditDateTime UpdateType
12 12-15-2015 18:09 1
45 12-04-2015 17:41 0
75 12-21-2015 04:26 0
12 12-17-2015 07:43 0
35 12-01-2015 05:36 1
45 12-15-2015 04:35 0
I'm trying to return only records where the UpdateType has changed from AuditDateTime based on the IDs. So in this example, ID 12 changes from the 12-15 entry to the 12-17 entry. I would want that record returned. There will be multiple instances of ID 12, and I need all records returned where an ID's UpdateType has changed from its previous entry. I tried adding a row_number but it didn't insert sequentially because the records are not in the table in order. I've done a ton of searching with no luck. Any help would be greatly appreciated.
By using a CTE it is possible to find the previous record based upon the order of the AuditDateTime
WITH CTEData AS
(SELECT ROW_NUMBER() OVER (PARTITION BY ID ORDER BY AuditDateTime) [ROWNUM], *
FROM #tmpTable)
SELECT A.ID, A.AuditDateTime, A.UpdateType
FROM CTEData A INNER JOIN CTEData B
ON (A.ROWNUM - 1) = B.ROWNUM AND
A.ID = B.ID
WHERE A.UpdateType <> B.UpdateType
The Inner Join back onto the CTE will give in one query both the current record (Table Alias A) and previous row (Table Alias B).
This should do what you're trying to do I believe
SELECT
T1.ID,
T1.AuditDateTime,
T1.UpdateType
FROM
dbo.My_Table T1
INNER JOIN dbo.My_Table T2 ON
T2.ID = T1.ID AND
T2.UpdateType <> T1.UpdateType AND
T2.AuditDateTime < T1.AuditDateTime
LEFT OUTER JOIN dbo.My_Table T3 ON
T3.ID = T1.ID AND
T3.AuditDateTime < T1.AuditDateTime AND
T3.AuditDateTime > T2.AuditDateTime
WHERE
T3.ID IS NULL
Alternatively:
SELECT
T1.ID,
T1.AuditDateTime,
T1.UpdateType
FROM
dbo.My_Table T1
INNER JOIN dbo.My_Table T2 ON
T2.ID = T1.ID AND
T2.UpdateType <> T1.UpdateType AND
T2.AuditDateTime < T1.AuditDateTime
WHERE
NOT EXISTS
(
SELECT *
FROM
dbo.My_Table T3
WHERE
T3.ID = T1.ID AND
T3.AuditDateTime < T1.AuditDateTime AND
T3.AuditDateTime > T2.AuditDateTime
)
The basic gist of both queries is that you're looking for rows where an earlier row had a different type and no other rows exist between the two rows (hence, they're sequential). Both queries are logically identical, but might have differing performance.
Also, these queries assume that no two rows will have identical audit times. If that's not the case then you'll need to define what you expect to get when that happens.
You can use the lag() window function to find the previous value for the same ID. Now you can pick only those rows that introduce a change:
select *
from (
select lag(UpdateType) over (
partition by ID
order by AuditDateTime) as prev_updatetype
, *
from YourTable
) sub
where prev_updatetype <> updatetype
Example at SQL Fiddle.
this is a simplified version of a problem I'm having,
I have two tables:
Table1 has two columns (Stuff, YesNo) and
Table2 has one column (Stuff)
The records in the YesNo Column will either be 1 or 0
How could I select records in Table2 where the records in Table1.YesNo = 1
Many Thanks
SELECT Table2.*
FROM Table2
INNER JOIN Table1 ON Table1.Stuff = Table2.Stuff
WHERE Table1.YesNo = 1
If I understand you correctly, this would be your solution:
Select Stuff From Table2
Where Exists (
Select 'Y'
From Table1
Where Table1.Stuff = Table2.Stuff
And YesNo = 1
)
As I believe you'll need data from both tables and you may want to render fields unique to each table This seems like a likely response. However, as I don't believe STUFF accurately represents the relationship... you'll need to quantify/adjust the on a.stuff = b.stuff so that the join includes all necessary fields.
SELECT A.Stuff, B.Stuff, B.YesNo
FROM table1 B
INNER JOIN table2 A
on A.Stuff = B.Stuff
WHERE B.YesNo = 1
SELECT T2.*
FROM TABLE1 T1
JOIN TABLE2 T2
ON T1.Stuff = T2.Stuff
WHERE T1.YesNo = 1
my_table has 4 columns: id integer, value integer, value2 integer, name character varying
I want all the records that:
have the same value2 as a record which name is 'a_name'
have a field value inferior to the one of a record which name is 'a_name'
And I have satisfying results with the following query:
select t.id
from my_table as t
where t.value < ( select value from my_table where name = 'a_name')
and s.value2 = (select value2 from my_table where name = 'a_name');
But is it possible to simplify this query with sql joins ?
Joining on the same table is still too much intricate in my mind. And I try to understand with this example.
What I happened so far trying, is a result full of dupplicates:
select t2.id
from my_table as t
inner join my_table as t2 on t2.value2 = t.value2
where t2.value < ( select value from my_table where name = 'a_name');
I think this will solve your problem.
select t1.id
from my_table as t1
join my_table as t2
on t1.value2 = t2.value2
and t2.name = 'a_name'
and t1.value < t2.value
You should use self join instead of inner join see this
http://msdn.microsoft.com/en-us/library/ms177490%28v=sql.105%29.aspx
You can always get distinct results by calling "SELECT distinct t2.id ..."
However, that will not enhance your understanding of inner joins. If you are willing, keep reading on. Let's start by getting all records with name = 'a_name'.
SELECT a.*
FROM my_table as a
WHERE a.name = 'a.name';
A simpler way to perform your inner joins is to understand that the result for the above query is yet another table, formally known as a relation. You can think of it as joining on the same table, but an easier way to think of it is as "joining on the result of this query". Lets put this to the test.
SELECT other.id
FROM my_table as a,
INNER JOIN my_table as other ON other.value2 = a.value2
WHERE a.name = 'a_name'
AND other.value < a.value;
If the first query (all rows with name = 'a_name') has many results, you stand a good chance of the second query having duplicates, because the inner join between aliases 'a' and 'other' is a subset of their cross product.
Edits: Grammar, Clarity
please try this
select t.id
from my_table as t
inner join
(select value from my_table where name = 'a_name')t1 on t.value<t1.value
inner join
(select value2 from my_table where name = 'a_name')t2 on t.value2=t2.value2
Hope the title makes some kind of sense - I'd basically like to do a nested select, based on a value in the original select, like so:
SELECT MAX(iteration) AS maxiteration,
(SELECT column
FROM table
WHERE id = 223652
AND iteration = maxiteration)
FROM table
WHERE id = 223652;
I get an ORA-00904 invalid identifier error.
Would really appreciate any advice on how to return this value, thanks!
It looks like this should be rewritten with a where clause:
select iteration,
col
from tbl
where id = 223652
and iteration = (select max(iteration) from tbl where id = 223652);
You can circumvent the problem alltogether by placing the subselect in an INNER JOIN of its own.
SELECT t.iteration
, t.column
FROM table t
INNER JOIN (
SELECT id, MAX(iteration) AS iteration
FROM table
WHERE id = 223652
) tm ON tm.id = t.id AND tm.iteration = t.iteration
Since you're using Oracle, I'd suggest using analytic functions for this:
SELECT * FROM (
SELECT col,
iteration,
row_number() over (partition by id order by iteration desc) rn
FROM tab
WHERE id = 223652
) WHERE rn = 1
do it like this:
with maxiteration as
(
SELECT MAX(iteration) AS maxiteration
FROM table
WHERE id = 223652
)
select
column,
iteration
from
table
where
id = 223652
AND iteration = maxiteration
;
Not 100% sure on Oracle syntax, but isn't it something like:
select iteration, column from table where id = 223652 order by iteration desc limit 1
I would approach this problem in a slightly different way. You're basically looking for the row that has no other iterations greater than it. There are at least 3 ways I can think of to do this:
SELECT
T1.iteration AS maxiteration,
T1.column
FROM
Table T1
WHERE
T1.id = 223652 AND
NOT EXISTS
(
SELECT *
FROM Table T2
WHERE
T2.id = 223652 AND
T2.iteration > T1.iteration
)
Or...
SELECT
T1.iteration AS maxiteration,
T1.column
FROM
Table T1
LEFT OUTER JOIN Table T2 ON
T2.id = T1.id AND
T2.iteration > T1.iteration
WHERE
T1.id = 223652 AND
T2.id IS NULL
Or...
SELECT
T1.iteration AS maxiteration,
T1.column
FROM
Table T1
INNER JOIN (SELECT id, MAX(iteration) AS maxiteration FROM Table T2 GROUP BY id) SQ ON
SQ.id = T1.id AND
SQ.maxiteration = T1.iteration
WHERE
T1.id = 223652
EDIT: I didn't see the ORA error the first time reading the question and it wasn't tagged as Oracle specific. I think that there may be some differences in the syntax and use of aliases in Oracle, so you may need to tweak some of the above queries.
The Oracle error is telling you that it doesn't know what maxiteration is, because the column alias isn't available yet inside the subquery. You need to refer to it by the table alias and column name instead of the column alias I believe.
You do something like
select maxiteration,column from table a join (select max(iteration) as maxiteration from table where id=1) b using (id) where b.maxiteration=a.iteration;
This could of course return multiple rows for one maxiteration unless your table has a constraint against it.
Here is my situation:
Table one contains a set of data that uses an id for an unique identifier. This table has a one to many relationship with about 6 other tables such that.
Given Table 1 with Id of 001:
Table 2 might have 3 rows with foreign key: 001
Table 3 might have 12 rows with foreign key: 001
Table 4 might have 0 rows with foreign key: 001
Table 5 might have 28 rows with foreign key: 001
I need to write a report that lists all of the rows from Table 1 for a specified time frame followed by all of the data contained in the handful of tables that reference it.
My current approach in pseudo code would look like this:
select * from table 1
foreach(result) {
print result;
select * from table 2 where id = result.id;
foreach(result2) {
print result2;
}
select * from table 3 where id = result.id
foreach(result3) {
print result3;
}
//continued for each table
}
This means that the single report can run in the neighbor hood of 1000 queries. I know this is excessive however my sql-fu is a little weak and I could use some help.
LEFT OUTER JOIN Tables2-N on Table1
SELECT Table1.*, Table2.*, Table3.*, Table4.*, Table5.*
FROM Table1
LEFT OUTER JOIN Table2 ON Table1.ID = Table2.ID
LEFT OUTER JOIN Table3 ON Table1.ID = Table3.ID
LEFT OUTER JOIN Table4 ON Table1.ID = Table4.ID
LEFT OUTER JOIN Table5 ON Table1.ID = Table5.ID
WHERE (CRITERIA)
Join doesn't do it for me. I hate having to de-tangle the data on the client side. All those nulls from left-joining.
Here's a set-based solution that doesn't use Joins.
INSERT INTO #LocalCollection (theKey)
SELECT id
FROM Table1
WHERE ...
SELECT * FROM Table1 WHERE id in (SELECT theKey FROM #LocalCollection)
SELECT * FROM Table2 WHERE id in (SELECT theKey FROM #LocalCollection)
SELECT * FROM Table3 WHERE id in (SELECT theKey FROM #LocalCollection)
SELECT * FROM Table4 WHERE id in (SELECT theKey FROM #LocalCollection)
SELECT * FROM Table5 WHERE id in (SELECT theKey FROM #LocalCollection)
Ah! Procedural! My SQL would look like this, if you needed to order the results from the other tables after the results from the first table.
Insert Into #rows Select id from Table1 where date between '12/30' and '12/31'
Select * from Table1 t join #rows r on t.id = r.id
Select * from Table2 t join #rows r on t.id = r.id
--etc
If you wanted to group the results by the initial ID, use a Left Outer Join, as mentioned previously.
You may be best off to use a reporting tool like Crystal or Jasper, or even XSL-FO if you are feeling bold. They have things built in to handle specifically this. This is not something the would work well in raw SQL.
If the format of all of the rows (the headers as well as all of the details) is the same, it would also be pretty easy to do it as a stored procedure.
What I would do: Do it as a join, so you will have the header data on every row, then use a reporting tool to do the grouping.
SELECT * FROM table1 t1
INNER JOIN table2 t2 ON t1.id = t2.resultid -- this could be a left join if the table is not guaranteed to have entries for t1.id
INNER JOIN table2 t3 ON t1.id = t3.resultid -- etc
OR if the data is all in the same format you could do.
SELECT cola,colb FROM table1 WHERE id = #id
UNION ALL
SELECT cola,colb FROM table2 WHERE resultid = #id
UNION ALL
SELECT cola,colb FROM table3 WHERE resultid = #id
It really depends on the format you require the data in for output to the report.
If you can give a sample of how you would like the output I could probably help more.
Join all of the tables together.
select * from table_1 left join table_2 using(id) left join table_3 using(id);
Then, you'll want to roll up the columns in code to format your report as you see fit.
What I would do is open up cursors on the following queries:
SELECT * from table1 order by id
SELECT * from table1 r, table2 t where t.table1_id = r.id order by r.id
SELECT * from table1 r, table3 t where t.table1_id = r.id order by r.id
And then I would walk those cursors in parallel, printing your results. You can do this because all appear in the same order. (Note that I would suggest that while the primary ID for table1 might be named id, it won't have that name in the other tables.)
Do all the tables have the same format? If not, then if you have to have a report that can display the n different types of rows. If you are only interested in the same columns then it is easier.
Most databases have some form of dynamic SQL. In that case you can do the following:
create temporary table from
select * from table1 where rows within time frame
x integer
sql varchar(something)
x = 1
while x <= numresults {
sql = 'SELECT * from table' + CAST(X as varchar) + ' where id in (select id from temporary table'
execute sql
x = x + 1
}
But I mean basically here you are running one query on your main table to get the rows that you need, then running one query for each sub table to get rows that match your main table.
If the report requires the same 2 or 3 columns for each table you could change the select * from tablex to be an insert into and get a single result set at the end...