I want update all values in my tables, but this can kill my database
UPDATE Table_1
SET Value = 'Some string with but changed'
where value = 'Some string without changes';
Can I do this by procedures, and it guarantee that it will not perform in infinty please i need some tips?
Edit
I read about cursors, but how can i use it
Your SQL seems fine and that is the preferred solution. A cursor will normally be far, far slower.
If you cannot create an index and the update above is really that slow, try the following. Considering I don't have the rest of the table definition to work with, I assume your primary key is a single field named ID:
First, create a temporary table with only the matching records:
CREATE TEMPORARY TABLE temp as
SELECT *
FROM Table_1
WHERE value = 'Some string without changes';
Then, update using this temporary table:
UPDATE Table_1 SET
Table_1.Value = 'Some string with but changed'
WHERE EXISTS (
SELECT *
FROM Temp
WHERE Temp.ID = Table_1.ID
);
Another approach if your DB is higher than 11g R1 version. Oracle has provided a beautiful package called DBMS_PARALLEL_EXECUTE which is used for large DMLS or any process which can be split into chunks and can be parallely done.
Related
I am new to Oracle. I have a table in Oracle which has 4 columns Period, Open_Flag,Creation_Dt,Updated_By.
The Period column is the Primary key of the table. I have created a proc which will check the value of period from input parameter in the table, if its existing, the value of Open_flag has to be updated else a new record shall be inserted.
create or replace
PROCEDURE PROC_REF_SAP_PERIOD(
V_PERIOD IN NUMBER,V_OPEN_FLAG IN VARCHAR2,V_CREATION_DT IN DATE,V_UPDATED_BY IN VARCHAR2)
AS
BEGIN
MERGE INTO REF_SAP_PERIOD T
USING (SELECT * FROM REF_SAP_PERIOD WHERE PERIOD=V_PERIOD )S
ON (T.PERIOD=S.PERIOD )
WHEN MATCHED THEN UPDATE SET OPEN_FLAG = V_OPEN_FLAG --WHERE PERIOD=V_PERIOD AND CREATION_DT=V_CREATION_DT AND UPDATED_BY=V_UPDATED_BY
WHEN NOT MATCHED THEN INSERT (PERIOD,OPEN_FLAG,CREATION_DT,UPDATED_BY) VALUES (V_PERIOD,V_OPEN_FLAG,V_CREATION_DT,V_UPDATED_BY);
END;
The issue is that the Update is working well in this case, however, the insert is not working. Please help.
You are merging table with itself, filtered by period. Obviously, it will never see your non-existent values in itself.
Try this line instead of your USING line:
using (select V_PERIOD "period" from dual)S
Am developing an application which helps people plan there schedule.
Lets say i have a table called 'Plan_Table' in which there are columns like
id,user_name, timestamp,place,event,plan_number.
For each day, a person can insert many records depending on his activities. I want 'plan_number' column to be populated by a trigger.
Suppose an user inserts five records at a time(in a batch). I want the plan_number field to be inserted as
plan_1
plan_1
plan_1
plan_1
plan_1
if he comes up with another plan.. and does few inserts, lets say 3 this time... I want the plan_number field to be inserted as
plan_2
plan_2
plan_2
How to achieve this using trigger and sequence?
Thanks in advance.
I think you can use the combination of the before statement level trigger for that table along with the global package variables and then use them in the Row Level trigger for that table.
Hope it gives you a heads up with the above logic
var_plan_number number := 0;
begin
if :new.plan_number is null then
select max(plan_number) into var_plan_number from plan_table where timestamp < CURRENT_TIMESTAMP - 5 --*some_treshold - ie 5 seconds*
and timestamp > CURRENT_TIMESTAMP and timestamp > trunc(sysdate) and user_name = :new.user_name;
--idea is to select max plan_number for current day and increment it by 1
--treshold should be set to time, your script is able to process batch records
var_plan_number := var_plan_number + 1;
:new.plan_number := var_plan_number;
end if;
that should do the trick...
Please consider this as a pseudo code, how your trigger should look like. There is no need for sequences.
The problem lies in the definition of "at a time (in a batch)". It will be difficult to tell the trigger when one batch ends and when a new one begins. It is possible with package variables, but the most competent place is your application.
I'd create a sequence to generate the ids, but pick up the ids in your application and feed them directly to the INSERT statement:
CREATE SEQUENCE myids;
CREATE TABLE plan_table(id int, user_name varchar2(30), mytimestamp, ...);
And in your code:
SELECT myids.nextval INTO myplanid FROM DUAL;
INSERT INTO plan_table(myplanid, myuser_name, SYSTIMESTAMP, place1 ...);
INSERT INTO plan_table(myplanid, myuser_name, SYSTIMESTAMP, place2 ...);
INSERT INTO plan_table(myplanid, myuser_name, SYSTIMESTAMP, place3 ...);
COMMIT;
Thanks for the answers you provided me. You really let me think in a purely db perspective.
As a web application developer, I thought, its a much better approach to use sequence/trigger to help me out with this problem. However, I found the solution from business logic of Application itself.
I am using Hibernate ORM for managing db tables. Hence i pulled out the max value of plan number using the following pieces of code.
Session session = getSessionFactory().openSession();
session.beginTransaction();
Criteria criteria = session.createCriteria(Mwwp_Plan.class).setProjection(Projections.max("plan_number"));
Integer maxPlanNumber = (Integer) criteria.uniqueResult();
session.getTransaction().commit();
System.out.println(maxPlanNumber);
if(maxPlanNumber==null)
{
System.out.println("maxPlanNumber is null");
maxPlanNumber = 0;
}
else
{
}
System.out.println("maxPlanNumber:"+maxPlanNumber);
return maxPlanNumber;
This is inside a function which my app uses to get the max(plan_number). If there is no plan_number in the table. It will give a default of 1.
Note: Mwwp_Plan is the name of table i used in my application.
Hence I achieved what i wanted.
Thanks for your help.
I am familiar with Sybase which allows queries with format: IF EXISTS () THEN ... ELSE ... END IF (or very close). This a powerful statement that allows: "if exists, then update, else insert".
I am writing queries for DB2 on IBM iSeries box. I have seen the CASE keyword, but I cannot make it work. I always receive the error: "Keyword CASE not expected."
Sample:
IF EXISTS ( SELECT * FROM MYTABLE WHERE KEY = xxx )
THEN UPDATE MYTABLE SET VALUE = zzz WHERE KEY = xxx
ELSE INSERT INTO MYTABLE (KEY, VALUE) VALUES (xxx, zzz)
END IF
Is there a way to do this against DB2 on IBM iSeries? Currently, I run two queries. First a select, then my Java code decides to update/insert. I would rather write a single query as my server is located far away (across the Pacific).
+UPDATE+
DB2 for i, as of version 7.1, now has a MERGE statement which does what you are looking for.
>>-MERGE INTO--+-table-name-+--+--------------------+----------->
'-view-name--' '-correlation-clause-'
>--USING--table-reference--ON--search-condition----------------->
.------------------------------------------------------------------------.
V |
>----WHEN--+-----+--MATCHED--+----------------+--THEN--+-update-operation-+-+----->
'-NOT-' '-AND--condition-' +-delete-operation-+
+-insert-operation-+
'-signal-statement-'
See IBM i 7.1 InfoCenter DB2 MERGE statement reference page
DB/2 on the AS/400 does not have a conditional INSERT / UPDATE statement.
You could drop the SELECT statement by executing an INSERT directly and if it fails execute the UPDATE statement. Flip the order of the statements if your data is more likely to UPDATE than INSERT.
A faster option would be to create a temporary table in QTEMP, INSERT all of the records into the temporary table and then execute a bulk UPDATE ... WHERE EXISTS and INSERT ... WHERE NOT EXISTS at the end to merge all of the records into the final table. The advantage of this method is that you can wrap all of the statements in a batch to minimize round trip communication.
You can perform control-flow logic (IF...THEN...ELSE) in an SQL stored procedure. Here's sample SQL source code:
-- Warning! Untested code ahead.
CREATE PROCEDURE libname.UPSERT_MYTABLE (
IN THEKEY DECIMAL(9,0),
IN NEWVALUE CHAR(10) )
LANGUAGE SQL
MODIFIES SQL DATA
BEGIN
DECLARE FOUND CHAR(1);
-- Set FOUND to 'Y' if the key is found, 'N' if not.
-- (Perhaps there's a more direct way to do it.)
SET FOUND = 'N';
SELECT 'Y' INTO FOUND
FROM SYSIBM.SYSDUMMY1
WHERE EXISTS
(SELECT * FROM MYTABLE WHERE KEY = THEKEY);
IF FOUND = 'Y' THEN
UPDATE MYTABLE
SET VALUE = NEWVALUE
WHERE KEY = THEKEY;
ELSE
INSERT INTO MYTABLE
(KEY, VALUE)
VALUES
(THEKEY, NEWVALUE);
END IF;
END;
Once you create the stored procedure, you call it like you would any other stored procedure on this platform:
CALL UPSERT_MYTABLE( xxx, zzz );
This slightly over complex piece of SQL procedure will solve your problem:
IBM Technote
If you want to do a mass update from another table then have a look at the MERGE statement which is an incredibly powerful statement which lets you insert, update or delete depending on the values from another table.
IBM DB2 Syntax
What are the other ways of achieving auto-increment in oracle other than use of triggers?
You can create and use oracle sequences. The syntax and details are at
http://www.techonthenet.com/oracle/sequences.php
Also read the article
http://rnyb2.blogspot.com/2006/02/potential-pitfall-with-oracle-sequence.html
to understand the limitations with respect to AUTONUMBER in other RDBMS
If you don't need sequential numbers but only a unique ID, you can use a DEFAULT of SYS_GUID(). Ie:
CREATE TABLE xxx ( ID RAW(16) DEFAULT SYS_GUID() )
A trigger to obtain the next value from a sequence is the most common way to achieve an equivalent to AUTOINCREMENT:
create trigger mytable_trg
before insert on mytable
for each row
when (new.id is null)
begin
select myseq.nextval into :new.id from dual;
end;
You don't need the trigger if you control the inserts - just use the sequence in the insert statement:
insert into mytable (id, data) values (myseq.nextval, 'x');
This could be hidden inside an API package, so that the caller doesn't need to reference the sequence:
mytable_pkg.insert_row (p_data => 'x');
But using the trigger is more "transparent".
As far as I can recall from my Oracle days, you can't achieve Auto Increment columns without using TRIGGER. Any solutions out there to make auto increment column involves TRIGGER and SEQUENCE (I'm assuming you already know this, hence the no trigger remarks).
Create a sequence:
create sequence seq;
Then to add a value
insert into table (id, other1, other2)
values (seq.nextval, 'hello', 'world');
Note: Look for oracle docs for more options about sequences (start value, increment, ...)
From 12c you can use an identity column, which makes explicit the link between table and auto-increment; there's no need for a trigger or a sequence. The syntax would be:
create table <table_name> ( <column_name> generated as identity );
In addition to e.g. FerranB's answer:
It is probably worth to mention that, as opposed to how auto_incement works in MySQL:
sequences work database wide, so they can be used for multiple tables and the values are unique for the whole database
therefore: truncating a table does not reset the 'autoincrement' functionaltiy
If you don't really want to use a "trigger-based" solution, you can achieve the auto-increment functionality with a programmatical approach, obtaining the value of the auto increment key with the getGeneratedKeys() method.
Here is a code snippet for your consideration:
Statement stmt = null;
ResultSet rs = null;
stmt = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_UPDATABLE);
stmt.executeUpdate("DROP TABLE IF EXISTS autoIncTable");
stmt.executeUpdate("CREATE TABLE autoIncTable ("
+ "priKey INT NOT NULL AUTO_INCREMENT, "
+ "dataField VARCHAR(64), PRIMARY KEY (priKey))");
stmt.executeUpdate("INSERT INTO autoIncTable (dataField) "
+ "values ('data field value')",
Statement.RETURN_GENERATED_KEYS);
int autoIncKeyFromApi = -1;
rs = stmt.getGeneratedKeys();
if (rs.next()) {
autoIncKeyFromApi = rs.getInt(1);
}
else {
// do stuff here
}
rs.close();
source: http://forums.oracle.com/forums/thread.jspa?messageID=3368856
SELECT max (id) + 1
FROM table
In Oracle, given a simple data table:
create table data (
id VARCHAR2(255),
key VARCHAR2(255),
value VARCHAR2(511));
suppose I want to "insert or update" a value. I have something like:
merge into data using dual on
(id='someid' and key='testKey')
when matched then
update set value = 'someValue'
when not matched then
insert (id, key, value) values ('someid', 'testKey', 'someValue');
Is there a better way than this? This command seems to have the following drawbacks:
Every literal needs to be typed twice (or added twice via parameter setting)
The "using dual" syntax seems hacky
If this is the best way, is there any way around having to set each parameter twice in JDBC?
I don't consider using dual to be a hack. To get rid of binding/typing twice, I would do something like:
merge into data
using (
select
'someid' id,
'testKey' key,
'someValue' value
from
dual
) val on (
data.id=val.id
and data.key=val.key
)
when matched then
update set data.value = val.value
when not matched then
insert (id, key, value) values (val.id, val.key, val.value);
I would hide the MERGE inside a PL/SQL API and then call that via JDBC:
data_pkg.merge_data ('someid', 'testKey', 'someValue');
As an alternative to MERGE, the API could do:
begin
insert into data (...) values (...);
exception
when dup_val_on_index then
update data
set ...
where ...;
end;
I prefer to try the update before the insert to save having to check for an exception.
update data set ...=... where ...=...;
if sql%notfound then
insert into data (...) values (...);
end if;
Even now we have the merge statement, I still tend to do single-row updates this way - just seems more a more natural syntax. Of course, merge really comes into its own when dealing with larger data sets.