I have a list of column names and loop over them to see if a name exists as a key in struct using 'StructKeyExists' - works as expected.
But when I try the same on a single row cfquery result it also works - I expected it to crash.
Why does it work on a cfquery results?
I'd expect to have issues if the cfquery result had more than 1 row, but in this case biz rules don't allow it.
It is checking the structure key not the individual rows in the query. So if you query has a column named "id" or "columnName" and you use structkeyexists to check for the key, e.g. "id" or "columnName" you are asking CFML if that query has a column named that. How many rows the query has returned is in no way related.
Related
I just want to check whether my query is correct. I have written a simple query on one table and against a field in that table where we are looking for all rows where the value in that field is starting with a certain characters and ending in certain characters, but must not contain certain characters in that field's value. Thus -
WHERE field_1 LIKE 'ABC%' AND field_1 LIKE '%XWY' AND field_1 NOT LIKE '%GHI12XY%'
The result is no rows, which is what we wanted, but I am not 100% sure whether the query is spot on and would like other whether this is correct
It looks correct to me. A good idea in all database software development is to create and load one or more test tables with rows that can be used to verify your logic. Then run your query against the test table(s) and see if you get the results you expect. Ideally, the rows in your test table will cover all the possibilities, for example, where you're supposed to get output, and where you're not supposed to get any.
I'm using SQL Server 2014 Express, and have a full-text index setup on a table.
The full-text index only indexes a single column, in this example named foo.
The table has 3 rows in it. The values in the 3 rows, for that full-text indexed column are like so ...
test 1
test 2
test 3 test 1
Each new line above is a new row in the table, and that text is literally what is in the full-text indexed column. So, using SQL Server's CONTAINS function, if I perform the following query, I get all rows back as matches, as expected.
SELECT * FROM example WHERE CONTAINS(foo, 'test')
But, if I run the following query, I also get all of the rows back as matches, which I am not expecting. In the following query, I only expected one row as a match.
SELECT * FROM example WHERE CONTAINS(foo, '"test 3"')
Lastly, simply searching for "3" returns no matching rows, which I also did not expect. I'd expect one matching row from the following query, but get none.
SELECT * FROM example WHERE CONTAINS(foo, '3')
I've read the MSDN pages on CONTAINS and full-text indexing, but I can't figure out this behavior. I must be doing something wrong.
Would anybody be able to explain to me what's happening and how to perform the searches I've described?
While this may not be the answer, it solved my original question. My full-text index was using the system stop list. For whatever reason, certain individual numbers, such as "1" in "test 1", were being skipped or whatever the stop list does.
The following question and answer, here on SO, suggested disabling the stop list alltogether. I did this and now my full text searches match as I expected them to, at the expense of a larger full text index, it looks like.
Full text search does not work if stop word is included even though stop word list is empty
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.
I have the probably unenviable task of writing a data migration query to populate existing records with a value for a new column being added to a table on a production database. The table has somewhere in the order of 200,000 rows.
The source of the value is in some XML that is stored in the database. I have some XPath that will pull out the value I want, and using extractValue to get the value out seems all good, until the number of records being updated by the query starts getting larger than the few I had in my test DB.
Once the record set grows to some random amount of size, somewhere around 500 rows, then I start getting the error "ORA-19025: EXTRACTVALUE returns value of only one node". Figuring that there was some odd row in the database for which there wasn't a unique result for the XPath, I tried to limit down the records in the query to isolate the bad record. But as soon as I shrunk the record set, the error disappeared. There is actually no row that will return more than one value for this XPath query. It looks like there's something fishy happening with extractValue.
Does anyone know anything about this? I'm not an SQL expert, and even then have spent more time on SQL Server than Oracle. So if I can't get this to work I guess I'm left to do some messing with cursors or something.
Any advice/help? If it helps, we're running 10g on the server. Thanks!
It's almost certain that at least one row from the table with the source XML has an invalid value. Rewrite the query to try and find it.
For example, use the XMLPath predicate that would give you the node in the second position (I don't currently have access to a db with XML objects, so I can't guarantee the following is syntactically perfect):
SELECT SourceKey
, EXTRACTVALUE(SourceXML, '/foo/bar/baz[1]')
, EXTRACTVALUE(SourceXML, '/foo/bar/baz[2]')
FROM SourceTable
WHERE EXTRACTVALUE(SourceXML, '/foo/bar/baz[2]') IS NOT NULL;
I use PostgreSQL database and C to connect to it. With a help from dyntest.pgc I can access to number of columns and their (SQL3) types from a result table of a query.
Problem is that when result table is empty, I can't fetch a row to get this data. Does anyone have a solution for this?
Query can be SELECT 1,2,3 - so, I think I can't use INFORMATION SCHEMA for this because there is no base table.
I'm not familiar with ecpg, but with libpq you should be able to call PQnfields to get the number of fields and then call various PQf* routines (like PQftype, PQfname) to get detailed info. Those functions take a PGResult, which you have even if there are no rows.
Problem is that when result table is empty, I can't fetch a row to get this data. Does anyone have a solution for this?
I am not sure to really get what you want, but it seems the answer is in the question. If the table is empty, there are no rows...
The only solution here seems you must wait a non empty result table, and then get the needed informations.