Forgive me but I'm relatively new to SQL.
I am trying to update a column of a table I created with a function I created but when I run the Update Statement, nothing happens, I just see the underscore flashing (I'm assuming its trying to run it). The Update Statement is updating around 60,000 fields so I assume it should take a little while but it's been 10 minutes and no good.
I would just like to know if anyone knows just some general reasons that the underscore may be flashing. I know this is super general but I've just never seen this before.
Here's an image of what I'm talking about:
http://i.imgur.com/Xk3kM2U.png?1
EDIT: There are exactly 67,662 records in the table.
I've also just screenshotted the query and linked it.
Your old-style joins have no join condition between the ap1/r1 pair and the ap2/r2 pair, so you're calling your calc_distance() function for 67,662 * 67,622 combinations of coordinates. The use of distinct is potentially a warning that you know you're getting duplicates. And then there is no correlation between the subquery and the update itself, so you're repeating that for each row in temproute. That will take a while.
It looks like you maybe don't want to be looking at the source airport from two copies of the route table; but the source and destination airports from a single copy.
Something like (untested):
UPDATE temproute tr
SET distance = (
SELECT calc_distance(ap2.latitude, ap2.longitude, ap1.latitude, ap1.longitude)
FROM routes r
JOIN airports ap1 ON ap1.icaoairport = r.sourceid
JOIN airports ap2 ON ap2.icaoairport = r.destid
WHERE r.routeid = tr.routeid
);
If temproute is a copy of route too, which the line count implies, then you don't need to refer to route directly at all in the subquery, perhaps.
But I'm speculating about what you're doing.
Related
There exists in my database a page_history table; the idea is that whenever a record in the page table is changed, that record's old values are stored in the history table.
My job now is to find occasions in which a record was changed, and retrieve the pre- and post-conditions of that change. Specifically, I want to know when a page changed groups, and what groups were involved in the change. The query I have below can find these instances, but with the use of the min function, I can only get back the values that match between the two records:
select page_id,
original_group,
min(created2) change_date
from (select h.page_id,
h.group_id original_group,
i.group_id new_group,
h.created_dttm created1,
i.created_dttm created2
from page_history h,
page_history i
where h.page_id = i.page_id
and h.created_dttm < i.created_dttm
and h.group_id != i.group_id)
group by page_id, original_group, created1
order by page_id
When I try to get, say, any details of the second record, like new_group, I'm hit with a ORA-00979: not a GROUP BY expression error. I don't want to group by new_group, though, because that's going to destroy the logic (I think it would find records displaying times a page changed from a group to another group, regardless of any changes to other groups in between).
My question, then, is how can I modify this query, or go about writing a new one, that achieves a similar end, but with the added availability of columns that do not match between the two records? In essence, how can I find that min record without sacrificing all the other columns I'm not trying to compare? I don't exactly need a complete answer, any suggestions that point me in the right direction would be appreciated.
I use PL/SQL Developer, and it looks like version 11.2.0.2.0 of Oracle.
EDIT: I have found a solution. It's not pretty, and I'd still like to see some alternatives, but if helping me out would threaten to explode your brain, I would advise relocating to an easier question.
Without seeing your table structure it's hard to re-write the query but when you have a min function used like that it invariably seems better to put it into a separate sub select to get what you want and then compare the result of that.
I have joined a new job where I am required to use FileMaker (and gradually transition systems to other databases). I have been a DB Admin of a MS SQL Server database for ~2 years, and I am very well versed in PL/SQL and T-SQL. I am trying to pan my SQL knowledge to FMP using the ExecuteSQL functionaloty, and I'm kinda running into a lot of small pains :)
I have 2 tables: Movies and Genres. The relevant columns are:
Movies(MovieId, MovieName, GenreId, Rating)
Genres(GenreId, GenreName)
I'm trying to find the movie with the highest rating in each genre. The SQL query for this would be:
SELECT M.MovieName
FROM Movies M INNER JOIN Genres G ON M.GenreId=G.GenreId
WHERE M.Rating=
(
SELECT MAX(Rating) FROM Movies WHERE GenreId = M.GenreId
)
I translated this as best as I could to an ExecuteSQL query:
ExecuteSQL ("
SELECT M::MovieName FROM Movies M INNER JOIN Genres G ON M::GenreId=G::GenreId
WHERE M::Rating =
(SELECT MAX(M2::Rating) FROM Movies M2 WHERE M2::GenreId = M::GenreId)
"; "" ; "")
I set the field type to Text and also ensured values are not stored. But all I see are '?' marks.
What am I doing incorrectly here? I'm sorry if it's something really stupid, but I'm new to FMP and any suggestions would be appreciated.
Thank you!
--
Ram
UPDATE: Solution and the thought process it took to get there:
Thanks to everyone that helped me solve the problem. You guys made me realize that traditional SQL thought process does not exactly pan to FMP, and when I probed around, what I realized is that to best use SQL knowledge in FMP, I should be considering each column independently and not think of the entire result set when I write a query. This would mean that for my current functionality, the JOIN is no longer necessary. The JOIN was to bring in the GenreName, which is a different column that FMP automatically maps. I just needed to remove the JOIN, and it works perfectly.
TL;DR: The thought process context should be the current column, not the entire expected result set.
Once again, thank you #MissJack, #Chuck (how did you even get that username?), #pft221 and #michael.hor257k
I've found that FileMaker is very particular in its formatting of queries using the ExecuteSQL function. In many cases, standard SQL syntax will work fine, but in some cases you have to make some slight (but important) tweaks.
I can see two things here that might be causing the problem...
ExecuteSQL ("
SELECT M::MovieName FROM Movies M INNER JOIN Genres G ON
M::GenreId=G::GenreId
WHERE M::Rating =
(SELECT MAX(M2::Rating) FROM Movies M2 WHERE M2::GenreId = M::GenreId)
"; "" ; "")
You can't use the standard FMP table::field format inside the query.
Within the quotes inside the ExecuteSQL function, you should follow the SQL format of table.column. So M::MovieName should be M.MovieName.
I don't see an AS anywhere in your code.
In order to create an alias, you must state it explicitly. For example, in your FROM, it should be Movies AS M.
I think if you fix those two things, it should probably work. However, I've had some trouble with JOINs myself, as my primary experience is with FMP, and I'm only just now becoming more familiar with SQL syntax.
Because it's incredibly hard to debug SQL in FMP, the best advice I can give you here is to start small. Begin with a very basic query, and once you're sure that's working, gradually add more complicated elements one at a time until you encounter the dreaded ?.
There's a number of great posts on FileMaker Hacks all about ExecuteSQL:
Since you're already familiar with SQL, I'd start with this one: The Missing FM 12 ExecuteSQL Reference. There's a link to a PDF of the entire article if you scroll down to the bottom of the post.
I was going to recommend a few more specific articles (like the series on Robust Coding, or Dynamic Parameters), but since I'm new here and I can't include more than 2 links, just go to FileMaker Hacks and search for "ExecuteSQL". You'll find a number of useful posts.
NB If you're using FMP Advanced, the Data Viewer is a great tool for testing SQL. But beware: complex queries on large databases can sometimes send it into fits and freeze the program.
The first thing to keep in mind when working with FileMaker and ExecuteSQL() is the difference between tables and table occurrences. This is a concept that's somewhat unique to FileMaker. Succinctly, tables store the data, but table occurrences define the context of that data. Table occurrences are what you're seeing in FileMaker's relationship graph, and the ExecuteSQL() function needs to reference the table occurrences in its query.
I agree with MissJack regarding the need to start small in building the SQL statement and use the Data Viewer in FileMaker Pro Advanced, but there's one more recommendation I can offer, which is to use SeedCode's SQL Explorer. It does require the adding of table occurrences and fields to duplicate the naming in your existing solution, but this is pretty easy to do and the file they offer includes a wizard for building the SQL query.
the problem story goes like:
consider a program to manage bank accounts with balance limits for each customer
{table Customers, table Limits} where for each Customer.id there's one Limit record
then the client said to store a history for the limits' changes, it's not a problem since I've already had date column for Limit but the active/latest limits's view-query needs to be changed
before: Customer-Limit was 1 to 1 so a simple select did the job
now: it would show all the Limits' records which means multiple records for each Customers and I need the latest Limits only so I thought of something like this pseudo code
foreach( id in Customers)
{
select top 1 *
from Limits
where Limits.customer_id = id
order by Limits.date
}
but while looking through SO for similar issues, I came across stuff like
"95% of the time when you need a looping structure in tSQL you are probably doing it wrong"-JohnFx
and
"SQL is primarily a set-orientated language - it's generally a bad idea to use a loop in it."-Mark Bannister
can anyone confirm/explain why is it wrong to loop? and in the explained problem above, what am I getting wrong that I need to loop?
thanks in advance
update : my solution
in light of TomTom's answer & suggested link here and before Dean kindly answered with code I came up with this
SELECT *
FROM Customers c
LEFT JOIN Limits a ON a.customer_id = c.id
AND a.date =
(
SELECT MAX(date)
FROM Limits z
WHERE z.customer_id = a.customer_id
)
thought I'd share :>
thanks for your response,
happy coding
Will this do?
;with l as (
select *, row_number() over(partition by customer_id order by date desc) as rn
from limits
)
select *
from customers c
left join l on c.customer_id = l.customer_id and l.rn = 1
I am assuming that earlier (i.e. before implementing the history functionality) you must be updating the Limits table. Now, for implementing the history functionality you have started inserting new records. Doesnt this trigger a lot of changes in your databases and code?
Instead of inserting new records, how about keeping the original functionality as is and creating a new table say Limits_History which will store all the old values from Limits table before updating it? Then all you need to do is fetch records from this table if you want to show history. This will not cause any changes in your existing SPs and code hence will be less error prone.
To insert record in the Limits_History table, you can simply create an AFTER TRIGGER and use the deleted magic table. Hence you need not worry about calling an SP or something to maintain history. The trigger will do this for you. Good examples of trigger are here
Hope this helps
It is wrong. You can do the same by quyting customers and limits with a subquery limiting to the most recent record on limit.
This is similar in concept to the query presented in Most recent record in a left join
You may have to do so in 2 joins - get most recent date, then get limit for the date. While this may look complex - it is a beginner issue, talk complex when you have sql statements reaching 2 printed pages and more ;)
Now, for an operational system the table design is broken - limits should contain the mos trecent limit, and a LimitHistory table the historical (or: all) entries, allowing fast retrieval of the CURRENT limit (which will be the one to apply to all transaction) without the overhead of the history. The table design you have assumes all limits are identical - that may be the truth (is the truth) for a reporting data warehouse, but is wrong for a transactional system as the history is not transacted.
Confirmation for why loop is wrong is exactly in the quoted parts in your question - SQL is a set-orientated language.
This means when you work on sets there's no reason to loop through the single rows, because you already have the 'result' (set) of data you want to work on.
Then the work you are doing should be done on the set of rows, because otherwise your selection is wrong.
That being said there are of course situations where looping is done in SQL and it will generally be done via cursors if on data, or done via a while loop if calculating stuff. (generally, exceptions always change).
However, as also mentioned in the quotes, often when you feel like using a loop you either shouldn't (it's poor performance) or you're doing logic in the wrong part of your application.
Basically - it is similar to how object orientated languages works on objects and references to said objects. Set based language works on - well, sets of data.
SQL is basically made to function in that manner - query relational data into result sets - so when working with the language, you should let it do what it can do and work on that. Just as if it was Java or any other language.
I tried to create a new view in my MS Access database so I can select better from it but I wonder what's happening here.
CREATE VIEW new
AS
SELECT msthread.id,
msthread.threadname,
Count(msthread.threadname) AS TotalPost,
threadcategory
FROM msthread
LEFT OUTER JOIN msposts
ON msthread.threadname = msposts.threadname
GROUP BY msthread.id,
msthread.threadname,
msthread.threadcategory
Access gives me this error message when I try to execute that statement.
Syntax error in create table statement
Is there specific problems in creating view with JOINs? I'm trying to access 2 tables.
CREATE VIEW was introduced with Jet 4 in Access 2000. But you must execute the statement from ADO/OleDb. If executed from DAO, it triggers error 3290, "Syntax error in CREATE TABLE statement", which is more confusing than helpful.
Also CREATE VIEW can only create simple SELECT queries. Use CREATE PROCEDURE for any which CREATE VIEW can't handle.
But CREATE VIEW should handle yours. I used a string variable to hold the DDL statement below, and then executed it from CurrentProject.Connection in an Access session:
CurrentProject.Connection.Execute strSql
That worked because CurrentProject.Connection is an ADO object. If you will be doing this from outside Access, use an OleDb connection.
Notice I made a few changes to your query. Most were minor. But I think the query name change may be important. New is a reserved word so I chose qryNew instead. Reserved words as object names seem especially troublesome in queries run from ADO/OleDb.
CREATE VIEW qryNew
AS
SELECT
mst.id,
mst.threadname,
mst.threadcategory,
Count(mst.threadname) AS TotalPost
FROM
msthread AS mst
LEFT JOIN msposts AS msp
ON mst.threadname = msp.threadname
GROUP BY
mst.id,
mst.threadname,
mst.threadcategory;
Going out on a limb here without the error message but my assumption is that you need an alias in front of your non-aliased column.
You may also have a problem titling the view as new. This is a problem with using a generic name for a view or table. Try giving it a distinct name that matters. I'll use msThreadPosts as an example.
CREATE VIEW msThreadPosts
AS
SELECT msthread.id,
msthread.threadname,
Count(msthread.threadname) AS TotalPost,
msposts.threadcategory --Not sure if you want msposts or msthread just pick one
FROM msthread
LEFT OUTER JOIN msposts
ON msthread.threadname = msposts.threadname
GROUP BY msthread.id,
msthread.threadname,
msthread.threadcategory
As long as we are looking at this query lets fix some other things that are being done in a silly way.
Lets start off with aliasing. If you alias a column you can very easily make your query easy to understand and read to anyone who is inclined to read it.
CREATE VIEW msThreadPosts
AS
SELECT mt.id,
mt.threadname,
Count(mt.threadname) AS TotalPost,
mp.threadcategory
FROM mtas mt
LEFT OUTER JOIN msposts mp
ON mt.threadname = mp.threadname
GROUP BY mt.id,
mt.threadname,
mt.threadcategory
There now doesn't that look better.
The next thing to look as if your column names. msthread has an id column. That column name is incredibly generic. This can cause problems when a column isn't aliased and an id exists in mulitple places or there are muliple id columns. Now if we change that column name to msthreadID it makes things much clearer. The goal is to design your tables in a way that anyone working on your database can imidiatley tell what a column is doing.
The next thing to look at is your join. Why are you joining on thread name? threadname is likely a character string and therefore not terribly efficient for joins. if msthread as an id column and needs to be joined to msposts then shouldn't msposts also have that id column to match up on to make joins more efficient?
In the process of fixing a poorly imported database with issues caused by using the wrong database encoding, or something like that.
Anyways, coming back to my question, in order to fix this issues I'm using a query of this form:
UPDATE table_name SET field_name =
replace(field_name,’search_text’,'replace_text’);
And thus, if the table I'm working on has multiple columns I have to call this query for each of the columns. And also, as there is not only one pair of things to run the find and replace on I have to call the query for each of this pairs as well.
So as you can imagine, I end up running tens of queries just to fix one table.
What I was wondering is if there is a way of either combine multiple find and replaces in one query, like, lets say, look for this set of things, and if found, replace with the corresponding pair from this other set of things.
Or if there would be a way to make a query of the form I've shown above, to run somehow recursively, for each column of a table, regardless of their name or number.
Thank you in advance for your support,
titel
Let's try and tackle each of these separately:
If the set of replacements is the same for every column in every table that you need to do this on (or there are only a couple patterns), consider creating a user-defined function that takes a varchar and returns a varchar that just calls replace(replace(#input,'search1','replace1'),'search2','replace2') nested as appropriate.
To update multiple columns at the same time you should be able to do UPDATE table_name SET field_name1 = replace(field_name1,...), field_name2 = replace(field_name2,...) or something similar.
As for running something like that for every column in every table, I'd think it would be easiest to write some code which fetches a list of columns and generates the queries to execute from that.
I don't know of a way to automatically run a search-and-replace on each column, however the problem of multiple pairs of search and replace terms in a single UPDATE query is easily solved by nesting calls to replace():
UPDATE table_name SET field_name =
replace(
replace(
replace(
field_name,
'foo',
'bar'
),
'see',
'what',
),
'I',
'mean?'
)
If you have multiple replaces of different text in the same field, I recommend that you create a table with the current values and what you want them replaced with. (Could be a temp table of some kind if this is a one-time deal; if not, make it a permanent table.) Then join to that table and do the update.
Something like:
update t1
set field1 = t2.newvalue
from table1 t1
join mycrossreferncetable t2 on t1.field1 = t2.oldvalue
Sorry didn't notice this is MySQL, the code is what I would use in SQL Server, my SQL syntax may be different but the technique would be similar.
I wrote a stored procedure that does this. I use this on a per database level, although it would be easy to abstract it to operate globally across a server.
I would just paste this inline, but it would seem that I'm too dense to figure out how to use the markdown deal, so the code is here:
http://www.anovasolutions.com/content/mysql-search-and-replace-stored-procedure