Can I create a view based on a nextval sequence?
I create a view like this:
create view seq_agents_nextval
as
select seq_agents.nextval from dual;
From the Oracle documentation I read that it doesn't work like that. Are there any other tricks or tips to create a view with output like that?
your best bet will be a udf in the spirit of the following code:
CREATE OR REPLACE FUNCTION my_nv RETURN INTEGER AS
l_rv NUMBER;
BEGIN
SELECT seq_agents.nextval
INTO l_rv
FROM DUAL
;
RETURN l_rv;
END;
CREATE OR REPLACE VIEW seq_agents_nextval AS
SELECT my_nv
FROM DUAL
;
otherwise you may query system views to get at least an approximate answer
CREATE OR REPLACE VIEW seq_agents_nextval AS
SELECT last_number + increment_by nv
FROM ALL_SEQUENCES
WHERE sequence_owner = '<the_proper_schema_name>'
AND sequence_name = 'SEQ_AGENTS'
;
but this value will be of limited use as it may be larger than the actual value by as much as the number of cached values for the sequence times the sequence increment and doesn't take into account the max value and carry-over behavior (the latter two aspects could be fixed).
keep in mind that an arbitrary number of new sequence values may be issued between you querying your view and using the returned value.
hope this helps & regards
Related
I'm playing around with array support in Oracle and hit a roadblock regarding array access within a SQL query. I'm using the following schema:
create type smallintarray as varray(10) of number(3,0);
create table tbl (
id number(19,0) not null,
the_array smallintarray,
primary key (id)
);
What I would like to do is get the id and the first element i.e. at index 1 of the array. In PostgreSQL I could write select id, the_array[1] from tbl t but I don't see how I could do that with Oracle. I read that array access by index is only possible in PL/SQL, which would be fine if I could return a "decorated cursor" to achieve the same result through JDBC, but I don't know if that's possible.
DECLARE
c1 SYS_REFCURSOR;
varr smallintarray2;
BEGIN
OPEN c1 FOR SELECT t.id, t.THE_ARRAY from tbl t;
-- SELECT t.THE_ARRAY INTO varr FROM table_with_enum_arrays2 t;
-- return a "decorated cursor" with varr(1) at select item position 1
dbms_sql.return_result(c1);
END;
You can do this in plain SQL; it's not pretty, but it does work. You would prefer that Oracle had syntax to hide this from the programmer (and perhaps it does, at least in the most recent versions; I am still stuck at 12.2).
select t.id, q.array_element
from tbl t cross apply
( select column_value as array_element,
rownum as ord
from table(the_array)
) q
where ord = 1
;
EDIT If order of generating the elements through the table operator is a concern, you could do something like this (in Oracle 12.1 and higher; otherwise the function can't be part of the query itself, but it can be defined on its own):
with
function select_element(arr smallintarray, i integer)
return number
as
begin
return arr(i);
end;
select id, select_element(the_array, 1) as the_array_1
from tbl
/
First of all, please don't do that on production. Use tables instead of storing arrays within a table.
Answer to your question is to use column as a table source
SELECT t.id, ta.*
from tbl t,
table(t.THE_ARRAY) ta
order by column_value
-- offset 1 row -- in case if sometime you'll need to skip a row
fetch first 1 row only;
UPD: as for ordering the array I can only say playing with 2asc/desc" parameters provided me with results I've expected - it has been ordered ascending or descending.
UPD2: found a cool link to description of performance issues might happen
Is it possible to set a trigger to set the new row's value to be the result of a select statement? My current syntax is as follows and it's just not working:
CREATE TRIGGER "BRAND_NEW_TRIGGER"
BEFORE INSERT ON my_table
FOR EACH ROW
BEGIN
:NEW.column_one := (SELECT details_col FROM other_table WHERE property_id = :NEW.property_id);
END;
/
I've fudged the details of the code above to protect my company's security, I know the code above doesn't make too much sense but there is a valid reason I need to pull and organise the data this way.
You can do a select into
select ot.details_col
into :new.column_one
from other_table ot
where ot.property_id = :new.property_id;
Of course, I'd strongly question the data model if this makes sense. That strongly implies that you've got a data model in need of some normalization.
Thank you for reply guys. I kind of solved my problem.
I used to try to update data with ref cursor in dynamic SQL using "where current of" but I now know that won't work.
Then I tried to use %rowtype to store both 'id' and 'clob' in one variable for future updating but turns out weak ref cursor can't use that type binding either.
After that I tried to use record as return of an ref cursor and that doesn't work on weak cursor either.
On the end, I created another cursor to retrieve 'id' separately along with cursor to retrieve 'clob' on the same time then update table with that id.
I'm now working on a Oracle data cleaning task and have a requirement like below:
There are 38 tables(maybe more in the future) and every table has one or multiple column which type is Clob. I need to find different keyword in those columns and according to a logic return binary label of the column and store it in a new column.
For example, there is a table 'myTable1' which has 2 Clob columns 'clob1' and 'clob2'. I'd like to find keyword 'sky' from those columns and store '0'(if not found) or '1'(if found) in two new columns 'clob1Sky','clob2Sky'.
I know if I could write it on a static way which will provide higher efficiency but I have to modify it for those very similar tasks every time. I want save some time on this so I'm trying to write it in a reusable way and not binding to certain table.
But I met some problem when writing the program. My program is like below:
create or replace PACKAGE body LABELTARGETKEYWORD
as
/**
#param varcher tableName: the name of table I want to work on
#param varchar colName: the name of clob column
#param varchar targetWord: the word I want to find in the column
#param varchar newColName: the name of new column which store label of clob
*/
PROCEDURE mainProc(tableName varchar, colName varchar,targetWord varchar,newColName varchar2)
as
type c_RecordCur is ref cursor;
c_sRecordCur c_recordCur;
/*other variables*/
begin
/*(1) check whether column of newColName exist
(2) if not, alter add table of newColName
(3) open cursor for retrieving clob
(4) loop cursor
(5) update set the value in newColName accroding to func labelword return
(6) close cursor and commit*/
end mainProc;
function labelWord(sRecord VARCHAR2,targetWord varchar2) return boolean...
function ifColExist(tableName varchar2,newColName varchar2) return boolean...
END LABELTARGETKEYWORD;
Most DML and DDL are written in dynamic sql way.
The problem is when I write the (5) part, I notice 'Where current of' clause can not be used in a ref cursor or dynamic sql statement. So I have to change the plan.
I tried to use a record(rowid,label) to store result and alter the table later.(the table only be used by two people in my group, so there won't be problem of lock and data changes). But I find because I'm trying to use dynamic sql so actually I have to define ref cursor with return of certain %rowtype and basically all other variables, %type in dynamic sql statement. Which makes me feel my method has something wrong.
My question are:
If there a way to define %type in dynamic sql? Binding type to variable in dynamic SQL?
Could anybody give me a hint how to write that (5) part in dynamic SQL?
Should not I design my program like that?
Is it not the way how to use dynamic SQL or PLSQL?
I'm very new to PL/SQL. Thank you very much.
According to Tom Kyte's advice, to do it in one statement if it can be done in one statement, I'd try to use a single UPDATE statement first:
CREATE TABLE mytable1 (id NUMBER, clob1 CLOB,
clob2 CLOB, clob1sky NUMBER, clob2sky NUMBER )
LOB(clob1, clob2) STORE AS SECUREFILE (ENABLE STORAGE IN ROW);
INSERT INTO mytable1(id, clob1, clob2)
SELECT object_id, object_name, object_type FROM all_objects
WHERE rownum <= 10000;
CREATE OR REPLACE
PROCEDURE mainProc(tableName VARCHAR2, colName VARCHAR2, targetWord VARCHAR2, newColName VARCHAR2)
IS
stmt VARCHAR2(30000);
BEGIN
stmt := 'UPDATE '||tableName||' SET '||newColName||'=1 '||
'WHERE DBMS_LOB.INSTR('||colName||','''||targetWord||''')>1';
dbms_output.put_line(stmt);
EXECUTE IMMEDIATE stmt;
END mainProc;
/
So, calling it with mainProc('MYTABLE1', 'CLOB1', 'TAB', 'CLOB1SKY'); fires the statement
UPDATE MYTABLE1 SET CLOB1SKY=1 WHERE DBMS_LOB.INSTR(CLOB1,'TAB')>1
which seems to do the trick:
SELECT * FROM mytable1 WHERE clob1sky=1;
id clob1 clob2 clob1sky clob2skiy
33 I_TAB1 INDEX 1
88 NTAB$ TABLE 1
89 I_NTAB1 INDEX 1
90 I_NTAB2 INDEX 1
...
I am not sure with your question-
If this job is suppose to run on daily or hourly basis ,running query through it will be very costly. One thing you can do - put all your clob data in a file and save it in your server(i guess it must be linux). then you can create a shell script and schedule a job to run gerp command and fetch your required value and "if found then update your table".
I think you should approaches problem another way:
1. Find all columns that you need:
CURSOR k_clobs
select table_name, column_name from dba_tab_cols where data_type in ('CLOB','NCLOB');
Or 2 cursor(you can build you query if you have more than 1 CLOB per table:
CURSOR k_clobs_table
select DISTINCT table_name from dba_tab_cols where data_type in ('CLOB','NCLOB');
CURSOR k_clobs_columns(table_namee varchar(255)) is
select column_name from dba_tab_cols where data_type in ('CLOB','NCLOB') and table_name = table_namee;
Now you are 100% that column you are checking is clob, so you don't have to worry about data type ;)
I'm not sure what you want achieve, but i hope it may help you.
I am getting below error while trying to copy data from one collection to other.
Error(17,8): PL/SQL: ORA-00904: "COLUMN_VALUE": invalid identifier
Please help me providing a better way.
create or replace type type_record as object(employee_id NUMBER(6),
first_name VARCHAR2(20));
create or replace type type_tbl as table of type_record;
create or replace function scrub_final_2 return sys_refcursor IS
x type_tbl;
test1 type_tbl;
y sys_refcursor;
z sys_refcursor;
begin
x:=type_tbl();
z:=scrub_final_1; /*This is a function which returns a refcursor*/
loop
fetch z bulk collect into test1;
exit when z%NOTFOUND;
select column_value bulk collect into x from table(test1);
end loop;
open y for select employee_id,first_name from employees a where not exists
(select employee_id from table(x) where a.employee_id=employee_id);
return y;
end;
First, using x, y, z, and test1 as variable names makes it relatively hard to understand your code since it is not obvious at any point which variables represent a cursor and which represent a collection. Calling an object type_record is also confusing since it is not, in fact, a record which is a PL/SQL structure very similar to a SQL object. Additionally, your title is rather confusing since neither of your collections are actually associative arrays.
Second, your loop as currently constructed doesn't make any sense. If you're going to have a loop, you'd want to do a bulk collect with a limit. If you're not going to use a limit in your bulk collect, there is no point in looping since you'll only ever have one iteration of the loop.
Third, there appears to be no reason to copy the data from one collection to another. You can use the data in test1 to open y rather than using x in the query. Using a second collection just means that you're wasting valuable space in the PGA.
Fourth, if you really do want to copy the data from one collection to another, you can do a simple assignment
x := test1;
Fifth, if you're going to write a select against a collection defined on an object type, the columns in the result will be the names of the object type's attributes. column_value is only a column name for collections of built-in types. If you really, really wanted to so the assignment the hard way with a select statement, you'd do something like
SELECT type_record( employee_id, first_name )
BULK COLLECT INTO x
FROM TABLE( test1 );
I have a simple table with one column of numbers. I want to load about 3000 numbers in it. I want to do that in memory, without using SQL*Loader. I tried
INSERT ALL
INTO t_table (code) VALUES (n1)
INTO t_table (code) VALUES (n2)
...
...
INTO t_table (code) VALUES (n3000)
SELECT * FROM dual
But I fails at 1000 values. What should I do ? Is SQL*Loader the only way ? Can I do LOAD with SQL only ?
Presumably you have an initial value of n. If so, this code will populate code with values n to n+2999 :
insert into t_table (code)
select (&N + level ) - 1
from dual
connect by level <=3000
This query uses a SQL*Plus substitution variable to post the initial value of n. Other clients will need to pass the value in a different way.
"Assume that I am in c++ with a stl::vector, what query should I
write ?"
So when you wrote n3000 what you really meant was n(3000). It's easy enough to use an array in SQL. This example uses one of Oracle's pre-defined collections, a table of type NUMBER:
declare
ids system.number_tbl_type;
begin
insert into t_table (code)
select column_value
from table ( select ids from dual )
;
end;
As for mapping your C++ vector to Oracle types, that's a different question (and one which I can't answer).