In my queries, I have used the unix_date function to group and count the data from backlogs to specific date. All works very well.
..
SELECT
*,
FROM
table1
FULL OUTER JOIN table2 USING (ID)
I'm not sure what should I add for the joining part to get a right query. I skipped the details of query as the query is quite long to be put on this post. Please let me know if you need the full query.
Problem: I think the join table append the row instead of just adding the column from joined query results because there are many same IDs in all tables (many-many relationship problem).However, not sure how to solve it.
Solved using composite key.
..
SELECT
*,
FROM
table1
FULL OUTER JOIN table2 USING (ID, Date)
Related
I have the following SQL query. In this query, I am left joining a table tblTestImport with access query named "unique". I am trying to integrate the query "unique" into the code below. I am not having any luck, please help.
DELETE tblTestImport.ID
FROM tblTestImport
WHERE tblTestImport.[ID]
in (SELECT tblTestImport.ID
FROM tblTestImport
LEFT JOIN **[unique]**
ON tblTestImport.ID = **unique.**LastOfID
WHERE (((**unique.**LastOfID) Is Null)));
Code for "unique" query
SELECT Last(tblTestImport.ID) AS LastOfID
FROM tblTestImport
GROUP BY tblTestImport.Url, tblTestImport.Kms, tblTestImport.Price, tblTestImport.Time;
Further info: I am trying to delete duplicates from the Access Table, and leave unique ones only.
tblTestImport has duplicate records. "Unique" query displays unique records. Then, I join tblTestImport table with "unique" query, to determine which unique records do not exist in tblTestImport. This gives me a list duplicates, which I want to delete.
Within the big chunk of code, i have [unique], which I would like replace with small piece of code below.
Your query will return no results, assuming that id is never NULL.
Why? Well unique.lastOfId is always a valid id in tblTestImport. As such, the LEFT JOIN will always match, and lastOfId will never be NULL.
So, no rows are in the subquery.
My suggestion is that you ask another question. Explain what you want to do and provide sample data and desired results.
It's hard to tell exactly what you're after based on the current setup of your question. However, this may be what you're looking for:
DELETE tblTestImport.ID
FROM tblTestImport
WHERE tblTestImport.[ID] IN
(SELECT tblTestImport.ID
FROM tblTestImport
LEFT JOIN [unique] ON tblTestImport.ID = unique.LastOfID
WHERE unique.LastOfID Is Null
AND tblTestImport.ID IN (
SELECT Last(tblTestImport.ID) AS LastOfID
FROM tblTestImport
GROUP BY tblTestImport.Url, tblTestImport.Kms, tblTestImport.Price, tblTestImport.Time)
)
(This is a simple nested query in the previous query, but it would all depend on the relationship of the data itself. This query assumes that they are linked on the same tblTestImport.ID field)
Try the following, untested:
DELETE FROM tblTestImport
WHERE ID <> (SELECT Min(ID) AS MinOfID FROM tblTestImport AS Dupe
WHERE (Dupe.Url= tblTestImport.Url)
AND (Dupe.Kms= tblTestImport.Kms)
AND (Dupe.Price= tblTestImport.Price)
AND (Dupe.Time= tblTestImport.Time));
Solution based on the following http://allenbrowne.com/subquery-01.html
The parameter is an ID that is the primary key for the table1. The other 3 tables contain details for reference against table1. Obviously if I cut out all the joins, I get only data from Table1, with any ID. I would really like to understand what is going on. Thanks.
SELECT
Detail14, Detail15, Detail16, //etc, etc
FROM
Table1
INNER JOIN
dbo.Table2 ON dbo.Table1.FK_AnID = dbo.Table2.PK_AnotherID
INNER JOIN
dbo.tblTable3 ON dbo.Table2.FK_Group = dbo.tblTable3.PK_RowID
LEFT JOIN
dbo.tblTable4 ON dbo.tblTable4.Name = dbo.Table1.Named
WHERE
PK_RefNumber = #AnID
Break this down by doing in steps. Use select * until you have the joins right, then go to the specific fields you want.
So get records for the first table with the where clause (if it is from the first table). Add the second table. If you get records,then that is not the source of the problem and add the third, etc.
Likely you are either joining on the wrong fields or you have an inner join where you need a left join.
I have five results to retrieve from a table and I want to write a store procedure that will return all desired rows.
I can write the query like that temporarily:
Select * from Table where Id = 1 OR Id = 2 or Id = 3
I supposed I need to receive a list of Ids to split, but how do I write the WHERE clause?
So, if you're just trying to learn SQL, this is a short and good example to get to know the IN operator. The following query has the same result as your attempt.
SELECT *
FROM TABLE
WHERE ID IN (SELECT ID FROM TALBE2)
This translates into what is your attempt. And judging by your attempt, this might be the simplest version for you to understand. Although, in the future I would recommend using a JOIN.
A JOIN has the same functionality as the previous code, but will be a better alternative. If you are curious to read more about JOINs, here are a few links from the most important sources
Joins - wikipedia
and also a visual representation of how different types of JOIN work
Another way to do it. The inner join will only include rows from T1 that match up with a row from T2 via the Id field.
select T1.* from T1 inner join T2 on T1.Id = T2.Id
In practice, inner joins are usually preferable to subqueries for performance reasons.
I am putting inner join in my query.I have got the result but didn't know that how the data is coming in output.Can anyone tell me that how the Inner join matching the data.Below I am showing a image.There are two table(One or Two Table).
According to me that first row it should be Mohit but output is different. Please tell me.
In SQL, the order of the output is not defined unless you specify it in the ORDER BY clause.
Try this:
SELECT *
FROM one
JOIN two
ON one.one_name = two.one_name
ORDER BY
one.id
You have to sort it if you want the data to come back a certain way. When you say you are expecting "Mohit" to be the first row, I am assuming you say that because "Mohit" is the first row in the [One] table. However, when SQL Server joins tables, it doesn't necessarily join in the order you think.
If you want the first row from [One] to be returned, then try sorting by [One].[ID]. Alternatively, you can order by any other column.
Avoid SELECT * in your main query.
Avoid duplicate columns: the JOIN condition ensures One.One_Name and two.One_Name will be equal therefore you don't need to return both in the SELECT clause.
Avoid duplicate column names: rename One.ID and Two.ID using 'aliases'.
Add an ORDER BY clause using the column names ('alises' where applicable) from the SELECT clause.
Suggested re-write:
SELECT T1.ID AS One_ID, T1.One_Name,
T2.ID AS Two_ID, T2.Two_name
FROM One AS T1
INNER JOIN two AS T2
ON T1.One_Name = T2.One_Name
ORDER
BY One_ID;
Add an ORDER BY ONE.ID ASC at the end of your first query.
By default there is no ordering.
SQL doesn't return any ordering by default because it's faster this way. It doesn't have to go through your data first and then decide what to do.
You need to add an order by clause, and probably order by which ever ID you expect. (There's a duplicate of names, thus I'd assume you want One.ID)
select * From one
inner join two
ON one.one_name = two.one_name
ORDER BY one.ID
I found this to be an issue when joining but you might find this blog useful in understanding how Joins work in the back.
How Joins Work..
[Edited]
#Shree Thank you for pointing that out.
On the paragraph of Merge Join. It mentions on how joins work...
Like
hash join, merge join consists of two steps. First, both tables of the
join are sorted on the join attribute. This can be done with just two
passes through each table via an external merge sort. Finally, the
result tuples are generated as the next ordered element is pulled from
each table and the join attributes are compared
.
I'm using MySQL and I'm trying to construct a query to do the following:
I have:
Table1 [ID,...]
Table2 [ID, tID, start_date, end_date,...]
What I want from my query is:
Select all entires from Table2 Where Table1.ID=Table2.tID
**where at least one** end_date<today.
The way I have it working right now is that if Table 2 contains (for example) 5 entries but only 1 of them is end_date< today then that's the only entry that will be returned, whereas I would like to have the other (expired) ones returned as well. I have the actual query and all the joins working well, I just can't figure out the ** part of it.
Any help would be great!
Thank you!
SELECT * FROM Table2
WHERE tID IN
(SELECT Table2.tID FROM Table1
INNER JOIN Table2 ON Table1.ID = Table2.tID
WHERE Table2.end_date < NOW
)
The subquery will select all tId's that match your where clause. The main query will use this subquery to filter the entries in table 2.
Note: the use of inner join will filter all rows from table 1 with no matching entry in table 2. This is no problem; these entries wouldn't have matched the where clause anyway.
Maybe, just maybe, you could create a sub-query to join with your actual tables and in this subquery you use a count() which can be used later on you where clause.