I'm having trouble to achieve the result I want trying join a column from a table twice.
My first table is "dbo.Sessions", which contains basic session info like the user ID, the project ID, login/logout date and times, etc.
I need to join to that the user names and project names. However, these are found in another table, but in the same column (dbo.tblObjects.Name).
Example:
+------+---------------+
| k_Id | Name |
+------+---------------+
| 1 | AgentName1 |
| 2 | ProjectNameX |
| 3 | ProjectNameY |
| 4 | AgentName2 |
| 5 | ProjectNameZ |
| 6 | AgentName3 |
+------+---------------+
To try and achieve my goal, I used two "LEFT JOIN". However, I get duplicate results in both. I'll either get both columns to display either the project names or the user names (depending on which "LEFT JOIN" is first).
This is what I have at this point:
SELECT SysDB.dbo.Sessions.*, SysDB.dbo.tblObjects.Name AS AgentName, SysDB.dbo.tblObjects.Name AS ProjectName
FROM SysDB.dbo.Sessions
LEFT JOIN SysDB.dbo.tblObjects ON SysDB.dbo.Sessions.userId = SysDB.dbo.Objects.k_Id
LEFT JOIN SysDB.dbo.tblObjects ON SysDB.dbo.Sessions.projectId = SysDB.dbo.Objects.k_Id
WHERE (SysDB.dbo.Sessions.loginDate BETWEEN 'm/d/yyyy' AND 'm/d/yyyy')
Note: SysDB is the name of the database that I identify every time because this query is to be run externally. I also don't use "USE SysDB" before my selection because it doesn't work from the VBA macro this will run from.
Note 2: I have found a thread on this site that addresses this exact issue, but I can't understand what is being done, and it dates back in 2012. Something about aliases. The solution offers to add "ls." and "lt." before the table names, but that doesn't work for me. Says the table doesn't exist.
SQL Query Join Same Column Twice
Note 3: I have tried many different things, such as:
LEFT JOIN SysDB.dbo.tblObjects AS AgentName ON SysDB.dbo.Sessions.userId = SysDB.dbo.tblObjects.k_Id
LEFT JOIN SysDB.dbo.tblObjects AS ProjectName ON SysDB.dbo.Sessions.projectId = SysDB.dbo.tblObjects.k_Id
Any insights would be greatly appreciated. Thanks!
You may find it much easier to see what you are doing by giving each table an alias (session, agent, project below)
SELECT session.*, agent.Name AS AgentName, project.Name AS ProjectName
FROM SysDB.dbo.Sessions session
LEFT JOIN SysDB.dbo.tblObjects agent
ON session.userId = agent.k_Id
LEFT JOIN SysDB.dbo.tblObjects project
ON project.projectId = session.k_Id
WHERE (session.loginDate BETWEEN 'm/d/yyyy' AND 'm/d/yyyy')
Related
I am working on a school assignment that has downright stumped me for days. The task is to, using a view (VAvailableGolfers), populate a list box with Golfers who are not tied to a given event/year selected from a combo box. Here is the data in the tables:
The expected output on the form, then, would be:
2015 shows Goldstein available
2016 shows no one available
2017 shows both Goldstein and Everett available
so, in other words, where there isn't a record in TGolferEventYears for a golfer for a particular year
I have tried left joins, full outer joins, exists, not in, not exists, etc and I cannot seem to nail down the SQL to make it happen.
Here is the VB Form and the SQL backing it. I cannot figure out what to code in the view:
"SELECT intGolferID, strLastName FROM vAvailableGolfers WHERE intEventYearID = " & cboEvents.SelectedValue.ToString
Here is the view, which I know isn't giving correct output:
select tg.intGolferID, strLastName, intEventYearID
from TGolferEventYears TGEY, TGolfers TG
Where tgey.intGolferID = tg.intGolferID
and intEventYearID not IN
(select intEventYearID
from TEventYears
where intEventYearID not in
(select intEventYearID
from TGolferEventYears))
Appreciate any help
I usually approach this type of question by using a cross join to generate all possibly combination and then a left join/where to filter out the ones that already exist:
select g.intGolferID, g.strLastName, ey.intEventYearID
from TEventYears ey cross join
TGolfers g left join
TGolferEventYears gey
on gey.intGolferID = g.intGolferID and
gey.intEventYearID = ey.intEventYearID
where gey.intGolferID is null;
Try this query:
SELECT tg.intGolferID, strLastName, tey.intEventYearID, tey.intEventYear
FROM TGolfers tg, TEventYears tey
WHERE tg.intGolferID NOT IN (
SELECT DISTINCT tgey.intGolferID
FROM TGolferEventYears tgey
WHERE tgey.intEventYearID = tey.intEventYearID
)
Explanation
Since you are trying to get combinations of data that is not in TGolferEventYears, you cannot use it in your outer-most SELECT as any of its columns would be NULL. Therefore, you need to SELECT FROM the tables that are the sources of that data, and going through each joined record, filter out the combinations that are in TGolferEventYears.
Main query
Select the data you need:
SELECT tg.intGolferID, strLastName, tey.intEventYearID, tey.intEventYear
...from TGolfers, cross join with TEventYears:
FROM TGolfers tg, TEventYears tey
...where the golfer ID does not exist in the following collection:
WHERE tg.intGolferID NOT IN ( ... )
Subquery
Select unique golfer IDs:
SELECT DISTINCT tgey.intGolferID
...from TGolferEventYears:
FROM TGolferEventYears tgey
...where the year is the current year of the outer query:
WHERE tgey.intEventYearID = tey.intEventYearID
Result
+-------------+-------------+----------------+--------------+
| intGolferID | strLastName | intEventYearID | intEventYear |
+-------------+-------------+----------------+--------------+
| 1 | Goldstein | 1 | 2015 |
| 1 | Goldstein | 3 | 2017 |
| 2 | Everett | 3 | 2017 |
+-------------+-------------+----------------+--------------+
I have a table that shows relationships between items and another table with the items themselves:
articles_to_articles
-------------------------
|articleID_1|articleID_2|
-------------------------
|12345 |67890 |
|23442 |343243 |
-------------------------
articles
-----------------------------------------------------
|article_id | article_name|lots | of | other | stuff|
-----------------------------------------------------
I am attempting to generate a file with that consists of the relationships from articles_to_articles but with the names in addition to the ids.
What I have so far is:
SELECT
a2a.articleID_1,
key_articles.article_name,
a2a.articleID_2,
val_articles.article_name
FROM
articles_to_articles a2a
INNER JOIN
articles key_articles
ON key_articles.articleID = articles_to_articles.articleID_1
INNER JOIN
articles val_articles
ON val_articles.articleID = articles_to_articles.articleID_2;
Access gives me a "missing operator" error but I can't seem to find the missing operator. What basic thing am I missing?
When joining more than two tables in MS Access, you must enclose each join within separate groups of parentheses, for example:
SELECT
a2a.articleID_1,
key_articles.article_name,
a2a.articleID_2,
val_articles.article_name
FROM
(
articles_to_articles a2a
INNER JOIN
articles key_articles
ON
key_articles.articleID = a2a.articleID_1
)
INNER JOIN
articles val_articles
ON
val_articles.articleID = a2a.articleID_2
I have two tables in an Access database, tblProducts and tblProductGroups.
I am trying to run a query that joins both of these tables, and brings back a single record for each product. The problem is that the current design allows for a product to be listed in the tblProductGroups table more than 1 - i.e. a product can be a member of more than one group (i didnt design this!)
The query is this:
select tblProducts.intID, tblProducts.strTitle, tblProductGroups.intGroup
from tblProducts
inner join tblProductGroups on tblProducts.intID = tblProductGroups.intProduct
where tblProductGroups.intGroup = 56
and tblProducts.blnActive
order by tblProducts.intSort asc, tblProducts.curPrice asc
At the moment this returns results such as:
intID | strTitle | intGroup
1 | Product 1 | 1
1 | Product 1 | 2
2 | Product 2 | 1
2 | Product 2 | 2
Whereas I only want the join to be based on the first matching record, so that would return:
intID | strTitle | intGroup
1 | Product 1 | 1
2 | Product 2 | 1
Is this possible in Access?
Thanks in advance
Al
This option runs a subquery to find the minimum intGoup for each tblProducts.intID.
SELECT tblProducts.intID
, tblProducts.strTitle
, (SELECT TOP 1 intGroup
FROM tblProductGroups
WHERE intProduct=tblProducts.intID
ORDER BY intGroup ASC) AS intGroup
FROM tblProducts
WHERE tblProducts.blnActive
ORDER BY tblProducts.intSort ASC, tblProducts.curPrice ASC
This works for me. Maybe this helps someone:
SELECT
a.Lagerort_ID,
FIRST(a.Regal) AS frstRegal,
FIRST(a.Fachboden) AS frstFachboden,
FIRST(a.xOffset) AS frstxOffset,
FIRST(a.yOffset) AS frstyOffset,
FIRST(a.xSize) AS frstxSize,
FIRST(a.ySize) AS frstySize,
FIRST(a.Platzgr) AS frstyPlatzgr,
FIRST(b.Artikel_ID) AS frstArtikel_ID,
FIRST(b.Menge) AS frstMenge,
FIRST(c.Breite) AS frstBreite,
FIRST(c.Tiefe) AS frstTiefe,
FIRST(a.Fachboden_ID) AS frstFachboden_ID,
FIRST(b.BewegungsDatum) AS frstBewegungsDatum,
FIRST(b.ErzeugungsDatum) AS frstErzeugungsDatum
FROM ((Lagerort AS a)
LEFT JOIN LO_zu_ART AS b ON a.Lagerort_ID = b.Lagerort_ID)
LEFT JOIN Regal AS c ON a.Regal = c.Regal
GROUP BY a.Lagerort_ID
ORDER BY FIRST(a.Regal), FIRST(a.Fachboden), FIRST(a.xOffset), FIRST(a.yOffset);
I have non unique entries for Lagerort_ID on the table LO_zu_ART. My goal was to only use the first found entry from LO_zu_ART to match into Lagerort.
The trick is to use FIRST() an any column but the grouped one. This may also work with MIN() or MAX(), but I have not tested it.
Also make sure to call the Fields with the "AS" statement different than the original field. I used frstFIELDNAME. This is important, otherwise I got errors.
Create a new query, qryFirstGroupPerProduct:
SELECT intProduct, Min(intGroup) AS lowest_group
FROM tblProductGroups
GROUP BY intProduct;
Then JOIN qryFirstGroupPerProduct (instead of tblProductsGroups) to tblProducts.
Or you could do it as a subquery instead of a separate saved query, if you prefer.
It's not very optimal, but if you're bringing in a few thousand records this will work:
Create a query that gets the max of tblProducts.intID from one table and call it qry_Temp.
Create another query and join qry_temp to the table you are trying to join against, and you should get your results.
I have a query I need to perform to show search results for a project. What needs to happen, I need to sort the results by the "horsesActiveDate" and this applies to all of them except for any ad with the adtypesID=7. Those results are sorted by date but they must always result after all other ads.
So I will have all my ads in the result set be ordered by the Active Date AND adtypesID != 7. After that, I need all adtypesID=7 to be sorted by Active Date and appended at the bottom of all the results.
I'm hoping to put this in one query instead of two and appending them together in PHP. The way the code is written, I have to find a way to get it all in one query.
So here is my original query which has worked great until I had to ad the adtypesID=7 which has different sorting requirements.
This is the query that exists now that doesn't take into account the adtypesID for sorting.
SELECT
horses.horsesID,
horsesDescription,
horsesActiveDate,
adtypesID,
states.statesName,
horses_images.himagesPath
FROM horses
LEFT JOIN states ON horses.statesID = states.statesID
LEFT JOIN horses_images ON horses_images.himagesDefault = 1 AND horses_images.horsesID = horses.horsesID AND horses_images.himagesPath != ''
WHERE
horses.horsesStud = 0
AND horses.horsesSold = 0
AND horses.horsesID IN
(
SELECT DISTINCT horses.horsesID
FROM horses
LEFT JOIN horses_featured ON horses_featured.horsesID = horses.horsesID
WHERE horses.horsesActive = 1
)
ORDER BY adtypesID, horses.horsesActiveDate DESC
My first thought was to do two queries where one looked for all the ads that did not contain adtypesID=7 and sort those as the query does, then run a second query to find only those ads with adtypesID=7 and sort those by date. Then take those two results and append them to each other. Since I need to get this all into one query, I can't use a php function to do that.
Is there a way to merge the two query results one after the other in mysql? Is there a better way to run this query that will accomplish this sorting?
The Ideal Results would be as below (I modified the column names so they would be shorter):
ID | Description | ActiveDate | adtypesID | statesName | himagesPath
___________________________________________________________________________
3 | Ad Text | 06-01-2010 | 3 | OK | image.jpg
2 | Ad Text | 05-31-2010 | 2 | LA | image1.jpg
9 | Ad Text | 03-01-2010 | 4 | OK | image3.jpg
6 | Ad Text | 06-01-2010 | 7 | OK | image5.jpg
6 | Ad Text | 05-01-2010 | 7 | OK | image5.jpg
6 | Ad Text | 04-01-2010 | 7 | OK | image5.jpg
Any help that can be provided will be greatly appreciated!
I am not sure about the exact syntax in MySQL, but something like
ORDER BY case when adtypesID = 7 then 2 else 1 end ASC, horses.horsesActiveDate DESC
would work in many other SQL dielects.
Note that most SQL dialects allow the order by to not only be a column, but an expression.
This should work:
ORDER BY (adtypesID = 7) ASC, horses.horsesActiveDate DESC
Use a Union to append two queries together, like this:
SELECT whatever FROM wherever ORDER BY something AND adtypesID!=7
UNION
SELECT another FROM somewhere ORDER BY whocares AND adtypesID=7
http://dev.mysql.com/doc/refman/5.0/en/union.html
I re-wrote your query as:
SELECT h.horsesID,
h.horsesDescription,
h.horsesActiveDate,
adtypesID,
s.statesName,
hi.himagesPath
FROM HORSES h
LEFT JOIN STATES s ON s.stateid = h.statesID
LEFT JOIN HORSES_IMAGES hi ON hi.horsesID = h.horsesID
AND hi.himagesDefault = 1
AND hi.himagesPath != ''
LEFT JOIN HORSES_FEATURED hf ON hf.horsesID = h.horsesID
WHERE h.horsesStud = 0
AND h.horsesSold = 0
AND h.horsesActive = 1
ORDER BY (adtypesID = 7) ASC, h.horsesActiveDate DESC
The IN subquery, using a LEFT JOIN and such, will mean that any horse record whose horsesActive value is 1 will be returned - regardless if they have an associated HORSES_FEATURED record. I leave it to you for checking your data to decide if it should really be an INNER JOIN. Likewise for the STATES table relationship...
I have two tables, one for routes and one for airports.
Routes contains just over 9000 rows and I have indexed every column.
Airports only 2000 rows and I have also indexed every column.
When I run this query it can take up to 35 seconds to return 300 rows:
SELECT routes.* , a1.name as origin_name, a2.name as destination_name FROM routes
LEFT JOIN airports a1 ON a1.IATA = routes.origin
LEFT JOIN airports a2 ON a2.IATA = routes.destination
WHERE routes_build.carrier = "Carrier Name"
Running it with "DESCRIBE" I get the followinf info, but I'm not 100% sure on what it's telling me.
id | Select Type | Table | Type | possible_keys | Key | Key_len | ref | rows | Extra
--------------------------------------------------------------------------------------------------------------------------------------
1 | SIMPLE | routes_build | ref | carrier,carrier_2 | carrier | 678 | const | 26 | Using where
--------------------------------------------------------------------------------------------------------------------------------------
1 | SIMPLE | a1 | ALL | NULL | NULL | NULL | NULL | 5389 |
--------------------------------------------------------------------------------------------------------------------------------------
1 | SIMPLE | a2 | ALL | NULL | NULL | NULL | NULL | 5389 |
--------------------------------------------------------------------------------------------------------------------------------------
The only alternative I can think of is to run two separate queries and join them up with PHP although, I can't believe something like this being something that could kill a mysql server. So as usual, I suspect I'm doing something stupid. SQL is my number 1 weakness.
Personally, I would start by removing the left joins and replacing them with inner joins as each route must have a start and end point.
It's telling you that it's not using an index for joining on the airports table. See how the "rows" column is so huge, 5000 odd? that's how many rows it's having to read to answer your query.
I don't know why, as you have claimed you have indexed every column. What is IATA? Is it Unique? I believe if mysql decides the index is inefficient it may ignore it.
EDIT: if IATA is a unique string, maybe try indexing half of it only? (You can select how many characters to index) That may give mysql an index it can use.
SELECT routes.*, a1.name as origin_name, a2.name as destination_name
FROM routes_build
LEFT JOIN
airports a1
ON a1.IATA = routes_build.origin
LEFT JOIN
airports a2
ON a2.IATA = routes_build.destination
WHERE routes_build.carrier = "Carrier Name"
From your EXPLAIN PLAN I can see that you don't have an index on airports.IATA.
You should create it for the query to work fast.
Name also suggests that it should be a UNIQUE index, since IATA codes are unique.
Update:
Please post your table definition. Issue this query to show it:
SHOW CREATE TABLE airports
Also I should note that your FULLTEXT index on IATA is useless unless you have set ft_max_word_len is MySQL configuration to 3 or less.
By default, it's 4.
IATA codes are 3 characters long, and MySQL doesn't search for such short words using FULLTEXT with default settings.
After you implement Martin Robins's excellent advice (i.e. remove every instance of the word LEFT from your query), try giving routes_build a compound index on carrier, origin, and destination.
It really depends on what information you're trying to get to. You probably don't need to join airports twice and you probably don't need to use left joins. Also, if you can search on a numeric field rather than a text field, that would speed things up as well.
So what are you trying to fetch?