I'm using SAP HANA and would like to join the output results of a procedure call inside a loop, is there anyway to do this?
Something similar to this: But the problem is the duplicate attribute name
FOR i IN 1..:nYEARS DO
CALL FUTUREREVENUES (:i,resulttemp);
result = SELECT * FROM :result t1
INNER JOIN :resulttemp t2
ON t1.ID = t2.ID
END FOR;
Nope, the main problem is not the duplicate attribute name; SAP HANA actually allows that in a projection, as long as the attribute is uniquely identifiable.
What you are trying to do here is not a good idea in any statically typed language, such as SQL. Basically, the structure of your return type result depends on the input, i.e. how often the loop gets executed.
What you would need here is some way of dynamic SQL that adjusts the projected column names with each iteration. While this appears to be a straightforward approach, it's actually the opposite.
Every consumer of the result data is forced to accept whatever the table comes out of this loop, without even knowing how the projected columns would be named.
That's hard to handle and makes the solution very little reusable.
An alternative approach could be to have a fixed output table structure, say 5 years forecast (if you can even predict anything that far with any certainty), and no dynamic column names.
Instead, you could e.g. name the columns FC+Year1, FC+Year2, ...
That way, the output structure stays the same and all the client application has to do, is to match the output labels according to the baseline year (the input into your prediction).
Related
I'm completely new to Visual FoxPro (9.0) and I was having trouble with creating a table which uses previous values to generate new values. What I mean by this is I have a given table that is two columns, age and probability of death. Using this I need to create a survival table which has the columns Age, l(x), d(x), q(x), m(x), L(x), T(x), and q(x) Where:
l(x): Survivorship Function; Defined as l(x+1) = l(x) * EXP(-m(x))
d(x): Number of Deaths; Defined as l(x) - l(x+1)
q(x): Probability of Death; This is given to me already
m(x): Mortality Rate; Defined as -LN(1-q(x))
L(x): Total Person-Years of Cohorts in the Interval (x, x+1); Defined as l(x+1) + (0.5 * d(x))
T(X): Total Person-Years of all Cohorts in the Interval (x, N); Defined as SUM(L(x)) [From x, N]
e(x): Remaining Life Expectancy; Defined as T(x) / l(x)
Now I'm not asking how to get all of these values, I just need help getting started and maybe pointed in the right direction. As far as I can tell, in VFP there is no way to point to a specific row in a data-table, so I can't do what I normally do in R and just make a loop. I.E. I can't do something like:
for (i in 1:length(given_table$Age))
{
new_table$mort_rate[i] <- -LN(1-given_table$death_prop[i])
}
It's been a little while so I'm not sure that's 100% correct anyway, but my point is I'm used to being able to create a table, and alter the values individually by pointing to a specific row and/or column using a loop with a simple counter variable. However, from what I've read there doesn't seem to be a way to do this in VFP, and I'm completely lost.
I've tried to make a Cursor, populating it with dummy values and trying to update each value sequentially using a SCATTER NAME and SCAN/REPLACE thing, but I don't really understand what's happening or how to fine tune this each calculation/entry that I need. (This is the post I was referencing when I tried this: Multiply and subtract values in previous row for new row in FoxPro.
So, how do I go about making a table that relies on iterative process to calculate subsequent values in Visual FoxPro? Are there any good resources that explain Cursors and the Scatter/Scan thing that I was trying (I couldn't find any resources that explained it in terms I could understand)?
Sorry if I've worded things poorly, I'm fairly new to programming in general. Thank you.
You absolutely can write a loop through an existing table in VFP. Use the SCAN command. However, if you're planning to add records to the same table as you go, you're going to run into some issues. Is that what you meant here? If so, my suggestion is to put the new records into a cursor as you create them and then APPEND them to the original table after you've processed all the records that were there when you started.
If you're putting records into a different table as you loop through the original, this is straightforward:
* Assumes you've already created the table or cursor to hold the result
SELECT YourOriginalTable && substitute in the alias/name for the original table
SCAN
* Do your calculations
* Substitute appropriately for YourNewTable and the two lists
INSERT INTO YourNewTable (<list of fields>) VALUES (<list of values>)
ENDSCAN
In the INSERT command, if you refer to any fields of the original table, you need to alias them, like this: YourOriginalTable.YourField, again substituting appropriately.
A bit too late but maybe still helps.
The steps to achieve what you want are:
0. close the tables - just in case (see CLOSE DATABASE)
open the Age table (see USE in VFP help)
create the Survival table structure (see CREATE TABLE)
for this you need to know the field type for each of your l(x), d(x), etc functions
Lets say that you named the fields like your functions (i.e. Lx,Dx, etc)
select the Age table (see SELECT)
loop through Age table (see SCAN)
pass each record into variables (see SCATTER)
made your calculations starting from the Age table data (variables) using L(x),D(x),etc formulas and store it into variables named as M.Your Survival Table Field
i.e. M.mx = -LOG(1-m.Age) && see LOG
Note: in these calculations you can use any mix of Age table variables and the new created variables.
after you calculated all the fields from Survival write it into table (see APPEND && GATHER commands)
close the tables (see CLOSE DATABASE)
Thank you for checking my question out!
I'm trying to write a query for a very specific problem we're having at my workplace and I can't seem to get my head around it.
Short version: I need to be able to target columns by their name, and more specifically by a part of their name that will be consistent throughout all the columns I need to combine or compare.
More details:
We have (for example), 5 different surveys. They have many questions each, but SOME of the questions are part of the same metric, and we need to create a generic field that keeps it. There's more background to the "why" of that, but it's pretty important for us at this point.
We were able to kind of solve this with either COALESCE() or CASE statements but the challenge is that, as more surveys/survey versions continue to grow, our vendor inevitably generates new columns for each survey and its questions.
Take this example, which is what we do currently and works well enough:
CASE
WHEN SURVEY_NAME = 'Service1' THEN SERV1_REC
WHEN SURVEY_NAME = 'Notice1' THEN FNOL1_REC
WHEN SURVEY_NAME = 'Status1' THEN STAT1_REC
WHEN SURVEY_NAME = 'Sales1' THEN SALE1_REC
WHEN SURVEY_NAME = 'Transfer1' THEN Null
ELSE Null
END REC
And also this alternative which works well:
COALESCE(SERV1_REC, FNOL1_REC, STAT1_REC, SALE1_REC) as REC
But as I mentioned, eventually we will have a "SALE2_REC" for example, and we'll need them BOTH on this same statement. I want to create something where having to come into the SQL and make changes isn't needed. Given that the columns will ALWAYS be named "something#_REC" for this specific metric, is there any way to achieve something like:
COALESCE(all columns named LIKE '%_REC') as REC
Bonus! Related, might be another way around this same problem:
Would there also be a way to achieve this?
SELECT (columns named LIKE '%_REC') FROM ...
Thank you very much in advance for all your time and attention.
-Kendall
Table and column information in Db2 are managed in the system catalog. The relevant views are SYSCAT.TABLES and SYSCAT.COLUMNS. You could write:
select colname, tabname from syscat.tables
where colname like some_expression
and syscat.tabname='MYTABLE
Note that the LIKE predicate supports expressions based on a variable or the result of a scalar function. So you could match it against some dynamic input.
Have you considered storing the more complicated properties in JSON or XML values? Db2 supports both and you can query those values with regular SQL statements.
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.
If I have a POCO class with ResultColumn attribute set and then when I do a Single<Entity>() call, my result column isn't mapped. I've set my column to be a result column because its value should always be generated by SQL column's default constraint. I don't want this column to be injected or updated from business layer. What I'm trying to say is that my column's type is a simple SQL data type and not a related entity type (as I've seen ResultColumn being used mostly on those).
Looking at code I can see this line in PetaPoco:
// Build column list for automatic select
QueryColumns = ( from c in Columns
where !c.Value.ResultColumn
select c.Key
).ToArray();
Why are result columns excluded from automatic select statement because as I understand it their nature is to be read only. So used in selects only. I can see this scenario when a column is actually a related entity type (complex). Ok. but then we should have a separate attribute like ComputedColumnAttribute that would always be returned in selects but never used in inserts or updates...
Why did PetaPoco team decide to omit result columns from selects then?
How am I supposed to read result columns then?
I can't answer why the creator did not add them to auto-selects, though I would assume it's because your particular use-case is not the main one that they were considering. If you look at the examples and explanation for that feature on their site, it's more geared towards extra columns you bring back in a join or calculation (like maybe a description from a lookup table for a code value). In these situations, you could not have them automatically added to the select because they are not part of the underlying table.
So if you want to use that attribute, and get a value for the property, you'll have to use your own manual select statement rather than relying on the auto-select.
Of course, the beauty of using PetaPoco is that you can easily modify it to suit your needs, by either creating a new attribute, like you suggest above, or modifying the code you showed to not exclude those fields from the select (assuming you are not using ResultColumn in other join-type situations).
I got a table with 75 columns,. what is the sql statement to display only the columns with values in in ?
thanks
It's true that a similar statement doesn't exist (in a SELECT you can use condition filters only for the rows, not for the columns). But you could try to write a (bit tricky) procedure. It must check which are the columns that contains at least one not NULL/empty value, using queries. When you get this list of columns just join them in a string with a comma between each one and compose a query that you can run, returning what you wanted.
EDIT: I thought about it and I think you can do it with a procedure but under one of these conditions:
find a way to retrieve column names dynamically in the procedure, that is the metadata (I never heard about it, but I'm new with procedures)
or hardcode all column names (loosing generality)
You could collect column names inside an array, if stored procedures of your DBMS support arrays (or write the procedure in a programming language like C), and loop on them, making a SELECT each time, checking if it's an empty* column or not. If it contains at least one value concatenate it in a string where column names are comma-separated. Finally you can make your query with only not-empty columns!
Alternatively to stored procedure you could write a short program (eg in Java) where you can deal with a better flexibility.
*if you check for NULL values it will be simple, but if you check for empty values you will need to manage with each column data type... another array with data types?
I would suggest that you write a SELECT statement and define which COLUMNS you wish to display and then save that QUERY as a VIEW.
This will save you the trouble of typing in the column names every time you wish to run that query.
As marc_s pointed out in the comments, there is no select statement to hide columns of data.
You could do a pre-parse and dynamically create a statement to do this, but this would be a very inefficient thing to do from a SQL performance perspective. Would strongly advice against what you are trying to do.
A simplified version of this is to just select the relevant columns, which was what I needed personally. A quick search of what we're dealing with in a table
SELECT * FROM table1 LIMIT 10;
-> shows 20 columns where im interested in 3 of them. Limit is just to not overflow the console.
SELECT column1,column3,colum19 FROM table1 WHERE column3='valueX';
It is a bit of a manual filter but it works for what I need.