I have a table with primary key column getting values from an oracle sequence. If I insert a record into my table, the best way would be -
INSERT INTO TABLE VALUES(SCHEMA.SEQUENCE.NEXTVAL, value1, value2, value3)
However, when I use save method from JPARepository, a select query for fetching only SCHEMA.SEQUENCE.NEXTVAL is run at time of object creation and then an additional INSERT query is run at end of transaction.
SELECT SCHEMA.SEQUENCE.NEXTVAL FROM DUAL
INSERT INTO TABLE VALUES(val_from_select_query, value1, value2, value3)
This is resulting in almost double time. Is there a way to configure my entity in such a way that it fetches sequence value in the insert query resulting in overall just 1 round trip to the DB?
What is the increment of the sequence?
Because this happens only for the first row you're inserting within the increment boundaries.
Given the increment is 50, when you insert multiple values (even with delay) you would see:
SELECT SCHEMA.SEQUENCE.NEXTVAL FROM DUAL
INSERT INTO TABLE VALUES(val_from_select_query, value1, value2, value3)
INSERT INTO TABLE VALUES(val_from_select_query+1, value1, value2, value3)
INSERT INTO TABLE VALUES(val_from_select_query+2, value1, value2, value3)
...
INSERT INTO TABLE VALUES(val_from_select_query+48, value1, value2, value3)
INSERT INTO TABLE VALUES(val_from_select_query+49, value1, value2, value3)
SELECT SCHEMA.SEQUENCE.NEXTVAL FROM DUAL
INSERT INTO TABLE VALUES(val_from_select_query2, value1, value2, value3)
INSERT INTO TABLE VALUES(val_from_select_query2+1, value1, value2, value3)
...
I usually set increment to 50 by create sequence a_sequence_name start with 1 increment by 50.
However this leads to some gaps in ids (1, 2, 3, 4, 5, 6, 7, 51, 52, 101) e.g. when restarting the application.
With the ID generation strategy GenerationType.AUTO, JPA (or rather underlying ORM framework) needs to know the generated ID so it can set it on the created object. As the INSERT statement does not return the ID, an additional SELECT is necessary.
On Oracle 12 you can use GenerationType.IDENTITY which will result in a single statement:
INSERT INTO <TABLE> (...) values (?) RETURNING <PRIMARY_KEY> INTO ?
Related
I am trying to create a unique index for a subset of data in a particular table. The existing data is something like this -
But the actual data should look like this -
The subset of rows will be the rows with the condition status as A or B. For these set of rows, the unique_id and amount value combination should be unique.
The DB2 version been used here is 9.7 on a windows server. Is partial index or conditional index possible in DB2?
New table
create or replace function generate_unique_det()
returns varchar(13) for bit data
deterministic
no external action
contains sql
return generate_unique();
create table test_unique (
unique_id int not null
, status char(1) not null
, amount int not null
, status2 varchar(13) for bit data not null generated always as
(case when status in ('A', 'B') then '' else generate_unique_det() end)
) in userspace1;
create unique index test_unique1 on test_unique (unique_id, amount, status2);
insert into test_unique (unique_id, status, amount)
values
(1234, 'A', 400)
--, (1234, 'B', 400)
, (1234, 'Z', 400)
, (1234, 'Z', 400);
The standard generate_unique function is not deterministic.
Such functions are not allowed in the generated always clause.
This is why we create our own function based on the standard one.
The problem with such a "fake" function could be, if Db2 not actually called this function for each updated / inserted row during a multi-row change operation (why to call the deterministic function multiple times on the same set of parameters, if it's enough to do it once and reuse the result for other affected rows afterwards). But it works in reality - Db2 does call such a function for every affected row, which is desired in our case.
You are not able to insert the commented out row in the last statement.
Existing table
set integrity for test_unique off;
alter table test_unique add
status2 varchar(13) for bit data not null
generated always as (case when status in ('A', 'B') then '' else generate_unique_det() end);
set integrity for test_unique immediate checked force generated;
-- If you need to save the rows violated future unique index
create table test_unique_exc like test_unique in userspace1;
-- If you don't need to save the the rows violated future unique index,
-- then just run the inner DELETE statement only,
-- which just removes these rows.
-- The whole statement inserts the deleted rows into the "exception table".
with d as (
select unique_id, status, amount, status2
from old table (
delete from (select t.*, rownumber() over (partition by unique_id, amount, status2) rn_ from test_unique t) where rn_>1
)
)
select count(1)
from new table (
insert into test_unique_exc select * from d
);
create unique index test_unique1 on test_unique (unique_id, amount, status2);
I have a list of values:
(56957,85697,56325,45698,21367,56397,14758,39656)
and a 'template' row in a table.
I want to do this:
for value in valuelist:
{
insert into table1 (field1, field2, field3, field4)
select value1, value2, value3, (value)
from table1
where ID = (ID of template row)
}
I know how I would do this in code, like c# for instance, but I'm not sure how to 'loop' this while passing in a new value to the insert statement. (i know that code makes no sense, just trying to convey what I'm trying to accomplish.
There is no need to loop here, SQL is a set based language and you apply your operations to entire sets of data all at once as opposed to looping through row by row.
insert statements can come from either an explicit list of values or from the result of a regular select statement, for example:
insert into table1(col1, col2)
select col3
,col4
from table2;
There is nothing stopping you selecting your data from the same place you are inserting to, which will duplicate all your data:
insert into table1(col1, col2)
select col1
,col2
from table1;
If you want to edit one of these column values - say by incrementing the value currently held, you simply apply this logic to your select statement and make sure the resultant dataset matches your target table in number of columns and data types:
insert into table1(col1, col2)
select col1
,col2+1 as col2
from table1;
Optionally, if you only want to do this for a subset of those values, just add a standard where clause:
insert into table1(col1, col2)
select col1
,col2+1 as col2
from table1
where col1 = <your value>;
Now if this isn't enough for you to work it out by yourself, you can join your dataset to you values list to get a version of the data to be inserted for each value in that list. Because you want each row to join to each value, you can use a cross join:
declare #v table(value int);
insert into #v values(56957),(85697),(56325),(45698),(21367),(56397),(14758),(39656);
insert into table1(col1, col2, value)
select t.col1
,t.col2
,v.value
from table1 as t
cross join #v as v
I'm currently going through the growing pains of trying to learn about functions and triggers. I'm trying to do a problem from a book I'm reading , but i dont understand how to do certain parts.
using this table
create table movies (
id integer primary key,
title varchar(255) not null,
year integer
);
insert into movies values (1, 'The Croods', 2013);
insert into movies values (2, 'Now You See Me', 2013);
insert into movies values (3, 'Argo', 2012);
insert into movies values (4, 'Jurassic World', 2015);
create table discs (
id integer primary key,
movie_id integer not null references movies(id),
type_id integer references disc_types(id),
price decimal(10,2),
available boolean
);
insert into discs values (1, 1, 1, 1.59, 't');
insert into discs values (2, 1, 1, 1.59, 'f');
insert into discs values (3, 1, 2, 2.99, 'f');
insert into discs values (4, 2, 1, 1.29, 't');
insert into discs values (5, 2, 1, 1.29, 't');
insert into discs values (6, 2, 2, 2.99, 't');
insert into discs values (7, 3, 2, 2.59, 't');
insert into discs values (8, 3, 2, 2.59, 't');
create table customers (
id integer primary key,
name varchar(255),
email varchar(255)
);
insert into customers values (1, 'John', 'john#hotmail.com');
insert into customers values (2, 'Jane', 'jane#gmail.com');
create table rentals (
id integer primary key,
customer_id integer not null references customers(id),
disc_id integer not null references discs(id),
date_rented date,
date_returned date
);
insert into rentals values (1, 1, 7, '2013-10-01', '2013-10-03');
insert into rentals values (2, 2, 5, '2013-10-05', '2013-10-06');
insert into rentals values (3, 2, 2, '2013-11-02', null);
insert into rentals values (4, 2, 3, '2013-11-02', null);
create table ratings (
customer_id integer not null references customers(id),
movie_id integer not null references movies(id),
rating integer,
primary key (customer_id, movie_id)
);
insert into ratings values (1, 1, 1);
insert into ratings values (1, 2, 4);
insert into ratings values (1, 3, 5);
insert into ratings values (2, 1, 4);
my logic was that i would have the new values of the ratings table that were going to be inserted or updated and use those to compare to whats in the rentals table to see if that customer had rented that movie already, if they did then they could enter a rating. but i cant transfer that logic in this lol. unless there an easier way to do this.
The loop inside the function complicates matters a bit, let's see if we can get rid of it. Your ratings table has a reference to customer and movie so we need a join.
SELECT COUNT(*) INTO rented FROM rentals WHERE disc_id IN
(SELECT id from discs INNER JOIN
rentals ON disc_id = discs.id where movie_id = new.movie_id)
AND customer_id = new.customer_id
Right this should make the logic of your stored procedure a lot easier. I am now leaving you to finish it because this after all is a learning exercise.
You need this sort of a join because it's more efficient and simpler than the loop. The ratings table has a reference to the movie_id but the rentals table only has a disc_id thus to find out if the user has rented a particular movie, you need to join it through the disc table.
You will need to change the return values. ref: http://www.postgresql.org/docs/9.2/static/plpgsql-trigger.html
Row-level triggers fired BEFORE can return null to signal the trigger
manager to skip the rest of the operation for this row (i.e.,
subsequent triggers are not fired, and the INSERT/UPDATE/DELETE does
not occur for this row). If a nonnull value is returned then the
operation proceeds with that row value
And also note that you do not do an INSERT inside your trigger function. You just return a non null value for the insert to proceed.
This is the EXISTS() version. (BTW: the definition for movies is missing)
CREATE OR REPLACE FUNCTION rate_only_rented()
RETURNS TRIGGER AS $func$
BEGIN
IF ( NOT EXISTS (
SELECT *
FROM rentals r
JOIN discs d ON r.disc_id = d.id
WHERE d.movie_id = NEW.movie_id
AND r.customer_id = NEW.customer_id
) ) THEN
RAISE EXCEPTION 'you(%) have not rented this movie(%) before'
, NEW.customer_id ,NEW.movie_id;
RETURN NULL;
ELSE
RETURN NEW;
END IF;
END;
$func$ language plpgsql;
And the trigger:
CREATE TRIGGER rate_only_rented
AFTER INSERT OR UPDATE
ON ratings
FOR EACH ROW
EXECUTE PROCEDURE rate_only_rented()
;
I have a table like this:
create table1 (field1 int,
field2 int default 5557,
field3 int default 1337,
field4 int default 1337)
I want to insert a row which has the default values for field2 and field4.
I've tried insert into table1 values (5,null,10,null) but it doesn't work and ISNULL(field2,default) doesn't work either.
How can I tell the database to use the default value for the column when I insert a row?
Best practice it to list your columns so you're independent of table changes (new column or column order etc)
insert into table1 (field1, field3) values (5,10)
However, if you don't want to do this, use the DEFAULT keyword
insert into table1 values (5, DEFAULT, 10, DEFAULT)
Just don't include the columns that you want to use the default value for in your insert statement. For instance:
INSERT INTO table1 (field1, field3) VALUES (5, 10);
...will take the default values for field2 and field4, and assign 5 to field1 and 10 to field3.
This works if all the columns have associated defaults and one does not want to specify the column names:
insert into your_table
default values
Try it like this
INSERT INTO table1 (field1, field3) VALUES (5,10)
Then field2 and field4 should have default values.
I had a case where I had a very simple table, and I basically just wanted an extra row with just the default values. Not sure if there is a prettier way of doing it, but here's one way:
This sets every column in the new row to its default value:
INSERT INTO your_table VALUES ()
Note: This is extra useful for MySQL where INSERT INTO your_table DEFAULT VALUES does not work.
If your columns should not contain NULL values, you need to define the columns as NOT NULL as well, otherwise the passed in NULL will be used instead of the default and not produce an error.
If you don't pass in any value to these fields (which requires you to specify the fields that you do want to use), the defaults will be used:
INSERT INTO
table1 (field1, field3)
VALUES (5,10)
You can write in this way
GO
ALTER TABLE Table_name ADD
column_name decimal(18, 2) NOT NULL CONSTRAINT Constant_name DEFAULT 0
GO
ALTER TABLE Table_name SET (LOCK_ESCALATION = TABLE)
GO
COMMIT
To insert the default values you should omit them something like this :
Insert into Table (Field2) values(5)
All other fields will have null or their default values if it has defined.
CREATE TABLE #dum (id int identity(1,1) primary key, def int NOT NULL default(5), name varchar(25))
-- this works
INSERT #dum (def, name) VALUES (DEFAULT, 'jeff')
SELECT * FROM #dum;
DECLARE #some int
-- this *doesn't* work and I think it should
INSERT #dum (def, name)
VALUES (ISNULL(#some, DEFAULT), 'george')
SELECT * FROM #dum;
CREATE PROC SP_EMPLOYEE --By Using TYPE parameter and CASE in Stored procedure
(#TYPE INT)
AS
BEGIN
IF #TYPE=1
BEGIN
SELECT DESIGID,DESIGNAME FROM GP_DESIGNATION
END
IF #TYPE=2
BEGIN
SELECT ID,NAME,DESIGNAME,
case D.ISACTIVE when 'Y' then 'ISACTIVE' when 'N' then 'INACTIVE' else 'not' end as ACTIVE
FROM GP_EMPLOYEEDETAILS ED
JOIN GP_DESIGNATION D ON ED.DESIGNATION=D.DESIGID
END
END
I have a database with companies and their products, I want for each
company to have a separate product id sequence.
I know that postgresql can't do this, the only way is to have a separate sequence for each company but this is cumbersome.
I thought about a solution to have a separate table to hold the sequences
CREATE TABLE "sequence"
(
"table" character varying(25),
company_id integer DEFAULT 0,
"value" integer
)
"table" will be holt the table name for the sequence, such as products, categories etc.
and value will hold the actual sequence data that will be used for product_id on inserts
I will use UPDATE ... RETURNING value; to get a product id
I was wondering is this solution efficient?
With row level locking, only users of same company adding rows in the same table will have to wait to get a lock and I think that reduces race condition problems.
Is there a better way to solve this problem?
I don't want to use a sequence for products table for all companies because the difference between product id's will be to big, I want to keep it simple for the users.
You could just embed a counter in your companies table:
CREATE TABLE companies (
id SERIAL PRIMARY KEY,
name TEXT,
product_id INT DEFAULT 0
);
CREATE TABLE products (
company INT REFERENCES companies(id),
product_id INT,
PRIMARY KEY (company, product_id),
name TEXT
);
INSERT INTO companies (id, name) VALUES (1, 'Acme Corporation');
INSERT INTO companies (id, name) VALUES (2, 'Umbrella Corporation');
Then, use UPDATE ... RETURNING to get the next product ID for a given company:
> INSERT INTO products VALUES (1, (UPDATE companies SET product_id = product_id+1 WHERE id=$1 RETURNING product_id), 'Anvil');
ERROR: syntax error at or near "companies"
LINE 1: INSERT INTO products VALUES (1, (UPDATE companies SET produc...
^
Oh noes! It seems you can't (as of PostgreSQL 9.1devel) use UPDATE ... RETURNING as a subquery.
The good news is, it's not a problem! Just create a stored procedure that does the increment/return part:
CREATE FUNCTION next_product_id(company INT) RETURNS INT
AS $$
UPDATE companies SET product_id = product_id+1 WHERE id=$1 RETURNING product_id
$$ LANGUAGE 'sql';
Now insertion is a piece of cake:
INSERT INTO products VALUES (1, next_product_id(1), 'Anvil');
INSERT INTO products VALUES (1, next_product_id(1), 'Dynamite');
INSERT INTO products VALUES (2, next_product_id(2), 'Umbrella');
INSERT INTO products VALUES (1, next_product_id(1), 'Explosive tennis balls');
Be sure to use the same company ID in both the product value and the argument to next_product_id(company INT).
Depending on how many companies you have, you could create a sequence for each company. Query it by a function which is set as a default on your product_id column.
Alternatively this function could simply do a SELECT FOR UPDATE and update the values of your table. Should be pretty performant I think.