Can database return partial results like a stream before the end of query execution? i know for some queries with like group by or order by we may need all the information before building the result. But for simple select, is it possible for a database to return data whenever it finds any? If it is, will it still be possible with JDBC.
I'm using Vertica, but it's a general question.
Thank you in advance.
Related
I would like to be able to tag an SQL query somehow, so I can relate the query execution to the web request that triggered the query. I already have a unique request id, that I tag my logs and other monitoring with, so I can easily do a complete trace across the weblogs and new relic for example.
But when I look at a report of long running SQL queries for example, I cannot trace that back to the request that triggered the SQL Query. I would really like to be able to tag the query with my request id somehow.
I can't find anything online. When I search I just find blogs about storing tags and tag clouds in SQL. Not really what I need.
Hope the question makes sense.
This is a very interesting post...
I hope, adding an extra nullable parameter to your stored procedure(s) will ensure that the profiler will catch the unique id passed during a call (in the trace) whether you use that parameter inside the procedure or not (i.e. to do something meaningful...like inserting into an audit table with unique id, procedure name, timestamp etc).
But I think that will make life difficult as you now have to update all your procedures.
If you already have logging turned on (web server) and it captures the same unique id in its request (log file) along with a timestamp then you probably can code a small utility app that reads the log file and find matching entries in the traced table by the timestamp alone.
The only thing that might go wrong is if your web server and database server have differeing times (you need to offset your calculation accordingly).
I don't know if this will help but it is certainly a very interesting project and I am hoping somebody have experienced this thing and came up with a nice solution.
Will be closely watching this post if such a solution exists....
All the best...
If I understand correctly, you want to follow up the query execution in Activity Monitor. But have you considered using a DMV or SQL PROFILER ?
In my opinion, your best bet would be to wrap it in a stored proc. This way you will be able to FILTER your trace only for this object. Here's an example of a simple select and the same select wrapped in stored proc named sproc1 :
As you can see in this image, you can start a SQL PROFILER trace and filter it on the ObjectName. You can then add other column like CPU, StartTime, ...
If you can't use a stored proc, then I would suggest to insert a comment before the exec like this:
/* ID1234 */
select * from table1
Then use SQL PROFILER the same way but you now filter on the TextData using your ID
Here the result :
I'm trying to create an Update Query in MS Access (2013) to a QuickBooks Database using QODBC.
I need to update the table PriceLevelPerItem. I am trying to update the field in said table called PriceLevelPerItemCustomprice with a value from another table, QueryThreeTable, and a column titled UpdatedPrice.
I need to update the table PriceLevelPerItem where the PriceLevelPerItemItemRefListID matches the value of ItemID from QueryThreeTable and ListID matches the QueryThreeTable.ItemListID (yes I know these are the wrong way around...)
So far this process has been a very annoying trial of many queries and any help would be greatly appreciated
This is what I've been working with:
UPDATE
PriceLevelPerItem
SET
(PriceLevelPerItemCustomPrice = QueryThreeTable.UpdatedPrice)
FROM
QueryThreeTable, PriceLevelPerItem
WHERE
QueryThreeTable.ItemID = PriceLevelPerItem.PriceLevelPerItemItemRefListID
AND
QueryThreeTable.ItemListID = PriceLevelPerItem.ListID;
I think the problem is that you're trying to use a DAO query inside a QODBC query. I think the two use different Data Access engines.
You're going to need to lookup your UpdatedPrice in your QueryThreeTable using DLookup. Or maybe you need to create a DAO loop using QueryThreeTable that then updates values in your QODBC table from there.
Make your QODBC query work without the use of QueryThreeTable and without any joins. Then come up with a way to dynamically create your query. You're resulting SQL should look something like this:
UPDATE
PriceLevelPerItem
SET
PriceLevelPerItemCustomPrice = 150.16
WHERE
PriceLevelPerItem.ListID = '310000-1146238368';
My project is in Visual Foxpro and I use MS SQL server 2008. When I fire sql queries in batch, some of the queries don't execute. However, no error is thrown. I haven't used BEGIN TRAN and ROLLBACK yet. What should be done ??
that all depends... You don't have any sample of your queries posted to give us an indication of possible failure. However, one thing I've had good response with from VFP to SQL is to build into a string (I prefer using TEXT/ENDTEXT for readabilty), then send that entire value to SQL. If there are any "parameter" based values that are from VFP locally, you can use "?" to indicate it will come from a variable to SQL. Then you can batch all in a single vs multiple individual queries...
vfpField = 28
vfpString = 'Smith'
text to lcSqlCmd noshow
select
YT.blah,
YT.blah2
into
#tempSqlResult
from
yourTable YT
where
YT.SomeKey = ?vfpField
select
ost.Xblah,
t.blah,
t.blah2
from
OtherSQLTable ost
join #tempSqlResult t
on ost.Xblah = t.blahKey;
drop table #tempSqlResult;
endtext
nHandle = sqlconnect( "your connection string" )
nAns = sqlexec( nHandle, lcSqlCmd, "LocalVFPCursorName" )
No I don't have error trapping in here, just to show principle and readability. I know the sample query could have easily been done via a join, but if you are working with some pre-aggregations and want to put them into temp work areas like Localized VFP cursors from a query to be used as your next step, this would work via #tempSqlResult as "#" indicates temporary table on SQL for whatever the current connection handle is.
If you want to return MULTIPLE RESULT SETs from a single SQL call, you can do that too, just add another query that doesn't have an "into #tmpSQLblah" context. Then, all instances of those result cursors will be brought back down to VFP based on the "LocalVFPCursorName" prefix. If you are returning 3 result sets, then VFP will have 3 cursors open called
LocalVFPCursorName
LocalVFPCursorName1
LocalVFPCursorName2
and will be based on the sequence of the queries in the SqlExec() call. But if you can provide more on what you ARE trying to do and their samples, we can offer more specific help too.
I have a question regarding SQL. I have the following SQL statement:
SELECT id, First, Last, E_Mail, Notes
FROM mytable
WHERE SOMETHING_SHOULD_BE_HERE IS NOT NULL;
I know that the SOMETHING_SHOULD_BE_HERE should be a column(attribute) in my table. Is their a way I can put a variable that can refer to the column I'm trying to access? In my case their are 30 columns. Can I have a string for SOMETHING_SHOULD_BE_HERE that can be assigned in my program to the column in which I want to search?
Thanks
No. Variables in SQL can refer to data, but not to object names (columns, functions or other database objects).
If you are building the SQL query, you'll need to use string operations to build your query.
The column can't be variable, but the value of the column can. The parser needs to know what to bind to.
If you elaborate on what you're trying to solve and which platform you're using it would allow for more complete answers.
You can have different SQLs queries in your code and use each one according to the case.
Another way is generate dynamically the query according the fields you want.
Without dynamic SQL, this is probably your best bet:
SELECT
id, first, last, email, notes
FROM
My_Table
WHERE
CASE #column_name_variable
WHEN 'column_1' THEN column_1
WHEN 'column_2' THEN column_2
...
ELSE 'not null'
END IS NOT NULL
There might be some issues with data type conversions, so you might need to explicitly cast all of the columns to one data type (VARCHAR is probably the best bet). Also, there's a good chance that performance will be horrendous on this query. I'd test it thoroughly before even thinking about implementing something like this.
I mentioned this in my comment, but for completeness I'll put it here too... you can probably also accomplish this with dynamic SQL, but how you do that will depend on your database server (MS SQL Server, Oracle, mySQL, etc.) and there are usually some caveats to using dynamic SQL.
In JDBC program, yes,the select statement can be composed like string operation.
for(String colName: colList)
{
String sql="Select id, First, Last, E_Mail, Notes From mytable where "+colName+" IS NOT NULL";
//execute the sql statement
}
It depends on how you are going to find out the value of SOMETHING_SHOULD_BE_HERE.
If you are in an Oracle PLS/SQL environment you could build up the WHERE clause using dynamic SQL and then use EXECUTE IMMEDIATE to execute it.
If you have a small set number of possibilities you could use CASE to workaround your problem possibly.
Your question is unclear.
However I am quite sure that what you have in mind is the so-called dynamic SQL (and related). "Dynamic SQL" allows you to dynamically build and submit queries at runtime. However such functionalities may not exist for your RDBMS.
There are several ways to do this.
When your query would return one and only one row
then you have to consider the EXECUTE IMMEDIATE statements (along with sp_executesql in tSQL : http://msdn.microsoft.com/en-us/library/ms188001.aspx ; or the USING clause in PL/SQL : http://docs.oracle.com/cd/B14117_01/appdev.101/b10807/13_elems017.htm to specify a list of input/output bind arguments) and/or PREPARED statements (http://rpbouman.blogspot.fr/2005/11/mysql-5-prepared-statement-syntax-and.html).
When your query can return more than one row
then you have to consider techniques such as the EXECUTE IMMEDIATE statement with the BULK COLLECT INTO clause or the OPEN-FOR, FETCH, and CLOSE statements (explicit cursors in PL/SQL :
http://docs.oracle.com/cd/B28359_01/appdev.111/b28370/dynamic.htm)
Please note that except in some particular cases, most conventional techniques like IF-THEN-ELSE and CASE statements should be preferred (along with a good algorithm). Furthermore they work with almost all RDBMS.
I'm using a DB2 database and I'm hoping for a query which will iterate over all stored procedures in a single database and print out the source code of each. No fancy formatting or performance requirements.
The reason for this (in case there's a better way of doing it) is I'm trying to track down usages of a particular table in our stored procs, so I want to be able to do a simple text search through all of them.
Also, I've got access to SQuirreL SQL client if anyone knows of a way via that.
Ah, figured it out. For other's reference:
select ROUTINENAME, TEXT from syscat.routines
where definer not in ('SYSIBM') AND ROUTINESCHEMA='databaseName'
I know this is old, but your answer started me on the right track. We are also using DB2, but don't have syscat.routines visible to us. However we do have SYSIBM.SYSROUTINES and that allows similar by doing
SELECT SCHEMA,
NAME,
TEXT
FROM SYSIBM.SYSROUTINES
WHERE SCHEMA = '<SCHEMA>'
and NAME = '<NAME>'
FOR FETCH ONLY WITH UR;