How to find inside Gemfire region, what column defined as key during data load ?
List and describe is not giving required info
Example i am.looking something smiler to oracke "ALL_CONSTRAINTS" where you can run following sql to find primary key
SELECT a.COLUMN_NAME
FROM all_cons_columns a INNER JOIN
all_constraints c
ON a.constraint_name = c.constraint_name
WHERE c.table_name = 'TBL'
AND c.constraint_type = 'P'
https://gemfire.docs.pivotal.io/98/geode/tools_modules/gfsh/command-pages/list.html
https://gemfire.docs.pivotal.io/98/geode/tools_modules/gfsh/command-pages/describe.html
I have found , please find correct solution here
query --query="select * from /region_name.keySet()"
I'm not entirely sure about what you mean by find inside Region, but my guess is that you're trying to find wether a particular entry exists within a given GemFire region.
If that's the case, then you can use the get method from the Region class. If you want to use GemFire SHell directly instead of a custom Java application, on the other hand, you can use the get command. Last, but not least, you could also execute a OQL query with the query command, as an example: query --query="SELECT e.value FROM /MyRegion.entries e WHERE e.key='myKey'"
Hope this helps. Cheers.
Related
I'm looking for a way to generate a script that would generate an SQL query that would select all child tables columns from a parent table.
Let's say you have a table Class (teacher, room, program) and a table Student (firstname, lastname, age, score, email).
Let's say you want to get a select of all students in Class.
Sure you could write the query manually.
But now imagine you have a complex table with dozens of child tables, how do you do this efficiently/programmatically ?
This is something that all programmers would like to have, no ?
I can't believe no one has ever done that.
I understand the answer may depend on the DBMS vendor, I'm personally looking for a solution for Oracle.
Questions that are a bit similar :
Oracle: Easy way to find names and/or number of child record tables
Postgres: select data from parent table and all child tables
And here is an idea to solve this partially : use a tool such as PowerBi or Visual Studio to generate Model from database in ASP.NET MVC. You won't get the SQL query but you will get the data.
You can start with this POC:
select
juc.table_name as parent_table,
/*
uc.table_name as child_table, uc.constraint_name, uc.r_constraint_name,
juc.constraint_type,
uccc.column_name as parent_col_name, uccc.position as parent_col_position,
uccp.column_name as child_col_name, uccp.position as child_col_position,
*/
'SELECT c.* FROM ' || juc.table_name || ' p JOIN ' || uc.table_name || ' c ON '
||
LISTAGG( 'c.' || uccp.column_name || ' = p.' || uccc.column_name, ' AND ' ) WITHIN GROUP(order by uccc.position)
as sql
from user_constraints uc
join user_constraints juc on juc.constraint_name = uc.r_constraint_name
join user_cons_columns uccc on uccc.constraint_name = uc.r_constraint_name
join user_cons_columns uccp on uccp.constraint_name = uc.constraint_name and uccc.position = uccp.position
where uc.constraint_type = 'R'
group by uc.table_name, juc.table_name, uc.constraint_name
;
You can create your own entity relationship model metadata and write PL/SQL that will traverse it and assemble SQL intelligently. I've done this myself to avoid having to hard-code SQL in my front-end apps. But it is highly complex and involves a lot of coding, far more than can be shared in a forum like this. But to give you the general gist, I have the following metadata tables that describe my model:
sql_statements - associates a logical entity with a primary table, and specifies the PK column.
sql_statement_parents - defines the parent entity and the child attribute used to join to the parent's PK.
sql_attribute_dictionary - lists every available attribute for every statement, the source column, its datatype, plus optional derived column expressions.
attribute_dependencies - used for derived column expressions, specifies which attributes are needed by the derived attribute.
Then you write code that takes a sql_statement name and a list of desired attributes and a set of optional filters, and it builds a list of needed source tables/columns using the data relationships in the metadata, and then using the parent-child relationships recursively builds SQL (using nested query blocks) from the child to whatever parent ancestor(s) it needs to obtain the required columns, intelligently aliasing everything and joining in the write way to be performant. It can then pass back the finished SQL as a REF CURSOR which you can then parse, open and fetch from to get results. It works great for me, but it did take weeks of work to perfect, and that's with decades of experience in SQL and PL/SQL. This is no simple task, but it is doable. And of course there are always complex needs that defy the capabilities of our metadata model, and so for those we end up either creating views or pipeline functions, and registering those in our metadata so that generated SQL can invoke them when needed.
But in the end, however you do it, you will not get away from having to describe your data model in detail so that code can walk it.
How does Oracle use COLUMN_ID as found in USER_TAB_COLUMNS view? I just need to confirm that it does not use this internal column ordering while creating implicit indexes - such as when a primary key is enforced or a unique key constraint is created (that is key/constraints columns provided are used in the same order - left to right and not these internal column ordering). (if possible please point me in the direction of Oracle documentation.). Thanks in advance.
It'll be hard to find something stating that it doesn't do something, but there isn't anything stating that it will use column_id to override the index creation.
You can see all the reference to column_id in the documentation here; the only one that seems matter is the all_tab_columns view.
You can verify the order of the columns as used in the index by querying the all_ind_columns view, where you will be able to see that there is no enforced relationship between its column_position - which comes from the order the columns are listed in the index creation command - and column_id.
If you are specifically interested in checking indexes that back up constraints, you can do something like:
select ac.owner, ac.table_name, ac.constraint_name, ac.index_owner,
ac.index_name, aic.column_position, aic.column_name
from all_constraints ac
join all_ind_columns aic on aic.index_owner = coalesce(ac.index_owner, ac.owner)
and aic.index_name = ac.index_name
order by 1, 2, 3, 6;
... adding filters for owner or table as needed.
I have a requirement to do a nested select within a where clause in a Hive query. A sample code snippet would be as follows;
select *
from TableA
where TA_timestamp > (select timestmp from TableB where id="hourDim")
Is this possible or am I doing something wrong here, because I am getting an error while running the above script ?!
To further elaborate on what I am trying to do, there is a cassandra keyspace that I publish statistics with a timestamp. Periodically (hourly for example) this stats will be summarized using hive, once summarized that data will be stored separately with the corresponding hour. So when the query runs for the second time (and consecutive runs) the query should only run on the new data (i.e. - timestamp > previous_execution_timestamp). I am trying to do that by storing the latest executed timestamp in a separate hive table, and then use that value to filter out the raw stats.
Can this be achieved this using hive ?!
Subqueries inside a WHERE clause are not supported in Hive:
https://cwiki.apache.org/confluence/display/Hive/LanguageManual+SubQueries
However, often you can use a JOIN statement instead to get to the same result:
https://karmasphere.com/hive-queries-on-table-data#join_syntax
For example, this query:
SELECT a.KEY, a.value
FROM a
WHERE a.KEY IN
(SELECT b.KEY FROM B);
can be rewritten to:
SELECT a.KEY, a.val
FROM a LEFT SEMI JOIN b ON (a.KEY = b.KEY)
Looking at the business requirements underlying your question, it occurs that you might get more efficient results by partitioning your Hive table using hour. If the data can be written to use this factor as the partition key, then your query to update the summary will be much faster and require fewer resources.
Partitions can get out of hand when they reach the scale of millions, but this seems like a case that will not tease that limitation.
It will work if you put in :
select *
from TableA
where TA_timestamp in (select timestmp from TableB where id="hourDim")
EXPLANATION : As > , < , = need one exact figure in the right side, while here we are getting multiple values which can be taken only with 'IN' clause.
Can I use Oracle sys tables to trace a path between two table, all the possibilities to go from X table to Y table.
The problem is:
I work on an enormous database, where it's really difficult to know rapidly, which tables are vital to make a join between two tables.
Can I do this?
First Need:
The problem with SQL Developer Data Modeler and the other tools, is the fact to have to select tables to rev_eng (So I should already know the tables to select) but for me, this is the major problem. In my case I have 800 tables and I can't select them all to trace the path. My desire is to submit as arguments two tables and then generate all the possible paths.
Second Need :
I have already try to query sys.all_constraints and the max I've done, is to detect the tables directly connected to a table X.
The query:
SELECT C1.TABLE_NAME,C2.TABLE_NAME
FROM ALL_CONSTRAINTS C1, ALL_CONSTRAINTS C2
WHERE C2.CONSTRAINT_NAME = C1.R_CONSTRAINT_NAME
AND UPPER(C1.OWNER) LIKE '**MY_SCHEMA**'
AND C1.CONSTRAINT_TYPE='R'
AND UPPER(C1.TABLE_NAME) LIKE '**X**'
ORDER BY C1.TABLE_NAME
So if somebody can help me to conceive at least the query to have this result:
Table1 | Table2 | JoinCollumnofTable1 | JoinCollumnofTable2
To have that, I surmise the other table to join to ALL_CONSTRAINTS is ALL_CON_COLUMNS
But the problem I've found is the composite primary_keys.
This is why Nature gave us data models: to assist in tasks like this.
If you don't have a data model then you can reverse engineer one from the data dictionary. See my answer to a question on reverse engineering.
Reverse engineering can only identify relationships which have been defined by foreign keys. This shouldn't need stating but let's say it anyway: if your database hasn't got constraints you have no chance of deriving a data model automatically.
"I have 800 tables and I can't select them all to trace the path. "
Hmmm, I suppose recommending you reverse engineer a data model is a bit like the punchline to the old joke about how to get to Cork: "Well I wouldn't start from here". The whole point about having a data model upfront is that we have it when when we really need it.
If primary and foreign key relationships are established in the database, you can use a tool like Oracle Developer with Data Modeler to reverse engineer the model and give a graphical representation of what the relationships are.
Tools like this read the Oracle dictionary to determine the relationships between tables. You can do this yourself by querying views such as sys.all_constraints.
I cobbled the following query together using Tim Hall's Generic Function Using a Ref Cursor, since I only have 10g here (you can use 11g's LISTAGG function if you've got 11g). It should get you close.
SELECT ac1.table_name "Table", ac2.table_name "Referencing Table"
, concatenate_list(CURSOR(SELECT acc.column_name
FROM all_cons_columns acc
WHERE acc.constraint_name = ac1.constraint_name
AND acc.owner = 'the_owner'
ORDER BY position)) "PK Columns"
, concatenate_list(CURSOR(SELECT acc.column_name
FROM all_cons_columns acc
WHERE acc.constraint_name = ac2.constraint_name
AND acc.owner = 'the_owner'
ORDER BY position)) "FK Columns"
FROM all_constraints ac1 JOIN all_constraints ac2
ON ac1.constraint_name = ac2.r_constraint_name
WHERE ac1.table_name = 'your_table'
AND ac1.owner = 'the_owner'
AND ac2.owner = 'the_owner'
AND ac1.constraint_type = 'P';
Also try schemaspy - an open source free alternative which uses the foreign keys to generate a relationship model!
I want to first get some result set (that includes two joins and selection), and then get the maximum value for one of the columns in the result set.
I need both the data in the original results set, and the max.
Is this possible with JDBC, and how?
I think it is. Should look like this:
SELECT MAX(derivedTable.myRow) FROM
(SELECT * FROM table1 JOIN table2 ON table1.id = table2.some_id) derivedTable
The key is to assign your inner select an alias ("derivedTable" above) and perform another selection on that.
--- Edit based on comment:
No, I don't think that's possible. Even without the JDBC layer - say, in a direct SQL console - I don't think there is a way to query data in a result set in any RDBMS I know.
Depending on the speed of your query and the size of the result, either performing a second query or just iterating through the results to find the maximum are your best options.
You can do it with standard SQL although it's a bit awkward:
SELECT a, b, c, (SELECT MAX(c) FROM table1 JOIN table2 ON table1.id = table2.table_id) max_c
FROM table1
JOIN table2 ON table1.id = table2.table_id