How does one do this? The SYSCOLUMNS system table only has columns for tables. SYSCHECKS has a REFERENCEDCOLUMNS object. Is there any way to get this.
I'm aware of the JDBC getPrimaryKeys call, but that doesn't get unique constraint columns.
Derby - constraints
It took some digging to find the above question; my question is a partially answered follow-up question to the one above.
Taking the CONSTRAINTID against SYSKEYS gives a CONGLOMERATEID, which when taken against SYSCONGLOMERATES yields a DESCRIPTOR. The DESCRIPTOR is a POJO that contains an int-array in the baseColumnPositions method. This int-array contains the COLUMNNUMBERS in SYSCOLUMNS of the columns in the constraint.
If querying in straight SQL, getting the DESCRIPTOR field yields a string with a CSV list of ints that have to be parsed. Fortunately for me, I happen to be working in Clojure, so calling the baseColumnPositions method and using the resulting int-array are trivial.
Related
Not much of a hbase guy so bear with me. Just a data analyst trying to do his job.
Let's say for the same of simplicity there's a hbase table called Student with the following info:
Key - Student ID
Value - SSN
So I'm trying to run the following command:
get 'Student_id','88812'
I'm trying to produce the following:
COLUMN CELL
H:00_ETAG timestamp=1525760141144, value=1234567891
However, nothing yields. After scanning the table I've come to discover that the key has some sort of hexidecimal value in front of it. So the key is actually like
\x80\x00\x02F188812
I understand that in order to execute the get command I'd just need to use double quotes like this
get 'Student',"\x80\x00\x02F188812"
Now where the real issue arises for me is the fact that I have NO clue what the hexadecimal prefix for each of these keys should be. It seems like the table that I'm working out of has a different hexadecimal prefix for each key. Is there a way that I can somehow execute the get command without the hexadecimal or at least find out what the hexadecimal should be? How about doing a reverse search where instead I try and find the key by searching by value?
And no, I can't scan the entire table since there are millions of records that exist.
I want to read from a table, change a couple column values for a few lines in a query, then update those lines on the same table.
I'm using SAP BODS, and that's what I tried:
I was about to insert images but just found out I can't insert images until 10 rep.
Anyway, I created a DataFlow where I have the same table as source and target.
A query to filter (using where) and change values (using mapping). And then a Table Comparison (where I expected those lines to be set to update, in this particular case), set table name on first entry, then PK in 'input primary key' and then the two columns I want to change in 'Compare columns'. No other changes from default that I can recall.
Got no warnings on 'validate all', and on execution I receive an ORA-00001 for the PK.
So ... I thought the Table Comparison would try to update, but seems like it's trying to insert instead. I want to know what I'm doing wrong and how could I get the job to do those updates. Thanks in advance.
Ps. I did search SO before asking and didn't find anything relevant.
Ok
So, turns out I just found what's going on a few minutes after posting the question.
Wasn't sure if I should answer my own question and took a look at this Etiquette for answering your own question
and decided to come back here and answer my own question.
For some reason I got stuck thinking that it was something to do with the Table Comparison trying to insert a line with a PK that's already there, instead of doing the update I wanted.
But after going back to the job to take another look at the issue, it occurred to me that maybe the problem could be a duplicate in the incoming data set. Made a few adjustment to filter those, and voilà.
I have a use case where i am mapping two tables to the same object.
In this object i have a string called source and I want to be able to set the table name or the database name to this variable.
Any ideas on how to achieve this?
I have thought about iterating over my list and manually setting it but this has the potential to waste a fair chunk of time.
I appreciate this is somewhat of an odd request so this may be the only way but am hoping for a solution that maps the source variable when hibernate is mapping everything else.
if i had understood correctly your issue , then your solution might be the MappedSuperClass , in which you must have an abstract class , which will have the common fields of the two tables and then you will extend that to the two entities you want , which will point to two different tables.
Check this link
You could try to achieve this with Load listener or Interceptors. In the listener/interceptor you can check what the data source is and populate the source field accordingly.
In the end i ended up using a formula to map my variable to a select statement which was sufficient for what i needed.
Say i have something like this:
somerecord SOMETABLE%ROWTYPE;
Is it possible to access the fields of somerecord with out knowing the fields names?
Something like somerecord[i] such that the order of fields would be the same as the column order in the table?
I have seen a few examples using dynamic sql but i was wondering if there is a cleaner way of doing this.
What i am trying to do is generate/get the DML (insert query) for a specific row in my table but i havent been able to find anything on this.
If there is another way of doing this i'd be happy to use but would also be very curious in knowing how to do the former part of this question - it's more versatile.
Thanks
This doesn't exactly answer the question you asked, but might get you the result you want...
You can query the USER_TAB_COLUMNS view (or the other similar *_TAB_COLUMN views) to get information like the column name (COLUMN_NAME), position (COLUMN_ID), and data type (DATA_TYPE) on the columns in a table (or a view) that you might use to generate DML.
You would still need to use dynamic SQL to execute the generated DML (or at least generate static SQL separately).
However, this approach won't work for identifying the columns in an arbitrary query (unless you create a view of it). If you need that, you might need to resort to DBMS_SQL (or other tools).
Hope this helps.
As far as I know there is no clean way of referencing record fields by their index.
However, if you have a lot of different kinds of updates of the same table each with its own column set to update, you might want to avoid dynamic sql and look in the direction of statically populating your record with values, and then issuing update someTable set row = someTableRecord where someTable.id = someTableRecord.id;.
This approach has it's own drawbacks, like, issuing an update to every, even unchanged column, and thus creating additional redo log data, but I believe it should be considered.
Background
I'm writing an adapter for ESE to .NET and LINQ in a Google Code project called eselinq. One important function I can't seem to figure out is how to get a list of indexes defined for a table. I need to be able to list available indexes so the LINQ part can automatically determine when indexes can be used. This will allow much more efficient plans for user queries if appropriate indexes can be found.
There are two related functions for querying index information:
JetGetTableIndexInfo - get index information by tableID
JetGetIndexInfo - get index information by tableName
These only differ in how the related table is specified (name or tableid). It sounds like these would support the function I want but all the info levels seem to require that I already have a certain index to query information for. The only exception is JET_IdxInfoCount, but that only counts how many indexes are present.
JET_IdxInfo with its JET_INDEXLIST sounds plausible but it only lists the columns on a specific index.
Alternatives
I am aware that I could get the index information another way, like annotations on .NET types corresponding to database tables, or by requiring a index mapping be provided ahead of time. I think there's enough introspection implemented to make everything else work out of the box without the user supplying extra information, except for this one function.
Another option may be to examine the system tables to find related index objects, but this is would mean depending on an undocumented interface.
To satisfy this question, I want a supported method of enumerating the indexes (just the name would be sufficient) on a table.
You are correct about JetGetTableIndexInfo and JetGetIndexInfo and JET_IdxInfo. The twist is that the data is returned in a somewhat complex: a temporary table is returned containing a row for the index and then a row for each column in the table. To just get the index names you will need to skip the column rows (the column count is given by the value of the columnidcColumn column in the first row).
For a .NET example of how to decipher this, look at the ManagedEsent project. In the MetaDataHelpers.cs file there is a method called GetIndexInfoFromIndexlist that extracts all the data from the temporary table.