We have a code to sort data and paginate the same and render the data to a Jqgrid. The code works fine when it is connected to an SQL server. That is on paginating each page returns distinct data as expected. But on connecting to an oracle server after some point of time the duplicate data are rendered. Both Oracle and SQL server has same data. Parameters in the Jqgrid page and the number of pages are working as expected on the server-side. That is on paging the start point and chunk size is correctly transferred to the server-side. The duplicate values are observed after sorting columns that are of type varchar in the database but hold numeric also. The database status column holds values of 3 and A, after sorting with the status column the duplicate data when the paginating issue is observed. Duplicate data in the sense, that data on page 2 will be the same as data on page 3. Any help will be appreciated. Thanks in advance...
Query One:-
select * from ( select row_.*, rownum rownum_ from ( Select x,y,z,status FROM tablename c WHERE status IN('in condition seperated with status') ORDER BY status asc ) row_ where rownum <= 30 ) where rownum_ > 20;
Query Two:-
select * from ( select row_.*, rownum rownum_ from ( Select x,y,z,status FROM tablename c WHERE status IN('in condition seperated with status') ORDER BY status asc ) row_ where rownum <= 20 ) where rownum_ > 10;
Here the query 1 and 2 always return the same results.
Where two or more values in the column of your ORDER BY clause are the same, you must always provide another secondary column to rank. Otherwise, data return has only a probability of fetching correct result as we expect. The possibility of getting a correct answer will be same as rolling a dice. The secondary column must be unique for accurate results. While you might be able to assume that they will sort themselves based on order entered
select * from( select row_.*, rownum rownum_ from( Select x,y,z,status FROM tablename c WHERE status IN('in condition seperated with status') ORDER BY status,x asc ) row_ where rownum <= 30 ) where rownum_ > 20;
Hoping x is a unique value. DBMS_RANDOM.VALUE can also be used in case if is an oracle specific query other than adding extra order by clause
I have JPA Native queries to an Oracle database. The only way I know to limit results is using 'rownum' in Oracle, but for some reason, query parser of a jar driver I have to use does not recognize it.
Caused by: java.sql.SQLException: An exception occurred when executing the following query: "/* dynamic native SQL query */ SELECT * from SFDC_ACCOUNT A where SBSC_TYP = ? and rownum <= ?". Cause: Invalid column name 'rownum'. On line 1, column 90. [parser-2900650]
com.compositesw.cdms.services.parser.ParserException: Invalid column name 'rownum'. On line 1, column 90. [parser-2900650]
How can I get rid of that?
ANSI Standard would be something like the following
SELECT *
FROM (
SELECT
T.*,
ROW_NUMBER() OVER (PARTITION BY T.COLUMN ORDER BY T.COLUMN) ROWNUM_REPLACE
FROM TABLE T
)
WHERE
1=1
AND ROWNUM_REPLACE < 100
or you could also use the following:
SELECT * FROM TABLE T
ORDER BY T.COLUMN
OFFSET 0 ROWS
FETCH NEXT 100 ROWS ONLY;
So I have a simple table with 5 or so columns, one of which is a clob containing some JSON data.
I am running
SELECT * FROM BIG_TABLE
SELECT * FROM BIG_TABLE WHERE ROWNUM < 2
SELECT * FROM BIG_TABLE WHERE ROWNUM = 1
SELECT * FROM BIG_TABLE WHERE ID=x
I expect that any fractionally intelligent relational database would return the data immediately. We are not imposing order by/group by clauses, so why not return the data as and when you find it?
Of all the forms of SELECT statements above, only 4. returned in a sub-second manner. This is unexpected for 1-3 which are returning between 1 and 10 minutes before the query shows any responses in SQL Developer. SQL Developer has the standard SQL Array Fetch Size of 50 (JDBC Fetch size of 50 rows) so at a minimum, it is taking 1-10 minutes to return 50 rows from a simple table with no joins on a super high-performance RAC cluster backed by fancy 4-tiered EMC disk subsystem.
Explain plans show a table scan. Fine, but why should I wait 1-10 minutes for the results with rownum in the WHERE clause?
What is going on here?
OK - I found the issue. ROWNUM does not operate like I thought it did and in the code above it never stops the full table scan.
This is because:
RowNum is assigned during the predicate operation (where clause evaluation) and incremented afterwards, i.e.: your row makes it into the result set and then gets rownum assigned.
In order to filter by rownum you need to already have it exist, something like ...
SELECT * FROM (SELECT * FROM BIG_TABLE) WHERE ROWNUM < 1
In effect what this means is that there is no way to filter out the top 5 rows from a table without having first selected the entire table if no other filter criteria are involved.
I solved my problem like this...
SELECT * FROM (SELECT * FROM BIG_TABLE WHERE
DATE_COL BETWEEN :Date1 AND :Date2) WHERE ROWNUM < :x;
A weird request maybe but. My boss wants me to create an admin version of a page we have that displays data from an oracle query in a table.
The admin page, instead of displaying the data (query returns 1 row), needs to return the table name and column name
Ex: Instead of:
Name Initial
==================
Bob A
I want:
Name Initial
============================
Users.FirstName Users.MiddleInitial
I realize I can do this in code but would rather just modify the query to return the data I want so I can leave the report generation code mostly alone.
I don't want to do it in a stored procedure.
So when I spit out the data in the report using something like:
blah blah = MyDataRow("FirstName")
I can leave that as is but instead of it displaying "BOB" it would display "Users.FirstName"
And I want to do the query using select * if possible instead of listing all the columns
So for each of the columns I am querying in the * , I want to get (instead of the column value) the tablename.ColumnName or tablename|columnName
hope you are following- I am confusing myself...
pseudo:
select tablename + '.' + Columnname as WhateverTheColumnNameIs
from Table1
left join Table2 on whatever...
Join Table_Names on blah blah
Whew- after writing all this I think I will just do it on the code side.
But if you are up for it maybe a fun challenge
Oracle does not provide an authentic way(there is no pseudocolumn) to get the column name of a table as a result of a query against that table. But you might consider these two approaches:
Extract column name from an xmltype, formed by passing cursor expression(your query) in the xmltable() function:
-- your table
with t1(first_name, middle_name) as(
select 1,2 from dual
), -- your query
t2 as(
select * -- col1 as "t1.col1"
--, col2 as "t1.col2"
--, col3 as "t1.col3"
from hr.t1
)
select *
from ( select q.object_value.getrootelement() as col_name
, rownum as rn
from xmltable('//*'
passing xmltype(cursor(select * from t2 where rownum = 1))
) q
where q.object_value.getrootelement() not in ('ROWSET', 'ROW')
)
pivot(
max(col_name) for rn in (1 as "name", 2 as "initial")
)
Result:
name initial
--------------- ---------------
FIRST_NAME MIDDLE_NAME
Note: In order for column names to be prefixed with table name, you need to list them
explicitly in the select list of a query and supply an alias, manually.
PL/SQL approach. Starting from Oracle 11g you could use dbms_sql() package and describe_columns() procedure specifically to get the name of columns in the cursor(your select).
This might be what you are looking for, try selecting from system views USER_TAB_COLS or ALL_TAB_COLS.
My application, which uses an Oracle database, is going slow or appears to have stopped completely.
How can find out which queries are most expensive, so I can investigate further?
This one shows SQL that is currently "ACTIVE":-
select S.USERNAME, s.sid, s.osuser, t.sql_id, sql_text
from v$sqltext_with_newlines t,V$SESSION s
where t.address =s.sql_address
and t.hash_value = s.sql_hash_value
and s.status = 'ACTIVE'
and s.username <> 'SYSTEM'
order by s.sid,t.piece
/
This shows locks. Sometimes things are going slow, but it's because it is blocked waiting for a lock:
select
object_name,
object_type,
session_id,
type, -- Type or system/user lock
lmode, -- lock mode in which session holds lock
request,
block,
ctime -- Time since current mode was granted
from
v$locked_object, all_objects, v$lock
where
v$locked_object.object_id = all_objects.object_id AND
v$lock.id1 = all_objects.object_id AND
v$lock.sid = v$locked_object.session_id
order by
session_id, ctime desc, object_name
/
This is a good one for finding long operations (e.g. full table scans). If it is because of lots of short operations, nothing will show up.
COLUMN percent FORMAT 999.99
SELECT sid, to_char(start_time,'hh24:mi:ss') stime,
message,( sofar/totalwork)* 100 percent
FROM v$session_longops
WHERE sofar/totalwork < 1
/
Try this, it will give you queries currently running for more than 60 seconds. Note that it prints multiple lines per running query if the SQL has multiple lines. Look at the sid,serial# to see what belongs together.
select s.username,s.sid,s.serial#,s.last_call_et/60 mins_running,q.sql_text from v$session s
join v$sqltext_with_newlines q
on s.sql_address = q.address
where status='ACTIVE'
and type <>'BACKGROUND'
and last_call_et> 60
order by sid,serial#,q.piece
v$session_longops
If you look for sofar != totalwork you'll see ones that haven't completed, but the entries aren't removed when the operation completes so you can see a lot of history there too.
Step 1:Execute the query
column username format 'a10'
column osuser format 'a10'
column module format 'a16'
column program_name format 'a20'
column program format 'a20'
column machine format 'a20'
column action format 'a20'
column sid format '9999'
column serial# format '99999'
column spid format '99999'
set linesize 200
set pagesize 30
select
a.sid,a.serial#,a.username,a.osuser,c.start_time,
b.spid,a.status,a.machine,
a.action,a.module,a.program
from
v$session a, v$process b, v$transaction c,
v$sqlarea s
Where
a.paddr = b.addr
and a.saddr = c.ses_addr
and a.sql_address = s.address (+)
and to_date(c.start_time,'mm/dd/yy hh24:mi:ss') <= sysdate - (15/1440) -- running for 15 minutes
order by c.start_time
/
Step 2: desc v$session
Step 3:select sid, serial#,SQL_ADDRESS, status,PREV_SQL_ADDR from v$session where sid='xxxx' //(enter the sid value)
Step 4: select sql_text from v$sqltext where address='XXXXXXXX';
Step 5: select piece, sql_text from v$sqltext where address='XXXXXX' order by piece;
You can use the v$sql_monitor view to find queries that are running longer than 5 seconds. This may only be available in Enterprise versions of Oracle. For example this query will identify slow running queries from my TEST_APP service:
select to_char(sql_exec_start, 'dd-Mon hh24:mi'), (elapsed_time / 1000000) run_time,
cpu_time, sql_id, sql_text
from v$sql_monitor
where service_name = 'TEST_APP'
order by 1 desc;
Note elapsed_time is in microseconds so / 1000000 to get something more readable
You can generate an AWR (automatic workload repository) report from the database.
Run from the SQL*Plus command line:
SQL> #$ORACLE_HOME/rdbms/admin/awrrpt.sql
Read the document related to how to generate & understand an AWR report. It will give a complete view of database performance and resource issues. Once we are familiar with the AWR report it will be helpful to find Top SQL which is consuming resources.
Also, in the 12C EM Express UI we can generate an AWR.
You can check the long-running queries details like % completed and remaining time using the below query:
SELECT SID, SERIAL#, OPNAME, CONTEXT, SOFAR,
TOTALWORK,ROUND(SOFAR/TOTALWORK*100,2) "%_COMPLETE"
FROM V$SESSION_LONGOPS
WHERE OPNAME NOT LIKE '%aggregate%'
AND TOTALWORK != 0
AND SOFAR <> TOTALWORK;
For the complete list of troubleshooting steps, you can check here:Troubleshooting long running sessions
select sq.PARSING_SCHEMA_NAME, sq.LAST_LOAD_TIME, sq.ELAPSED_TIME, sq.ROWS_PROCESSED, ltrim(sq.sql_text), sq.SQL_FULLTEXT
from v$sql sq, v$session se
order by sq.ELAPSED_TIME desc, sq.LAST_LOAD_TIME desc;