Let's say I have two tables A and B.
Table B has a foreign key that references Table A's primary key.
And the foreign key has 'on delete cascade' constraint.
And I am also using Java and JDBC to access this database.
How do I know the number of rows of Table B affected by delete cascade constraint?
I have to get the number in Java Application.
Does connection object or something has any parameter or method that returns it?
To follow after DELETE FROM statement you can use an audit table and BEFORE DELETE trigger.
// change type of deleted_id to your primary key's type.
create table deleted_audit ( deleted_id BIGINT, dt TIMESTAMP, count INT );
DELIMITER $$
CREATE TRIGGER count_deleted BEFORE delete ON a
FOR EACH ROW
BEGIN
DECLARE count_items INT;
SELECT count(*) FROM b WHERE a_id=OLD.id INTO count_items;
INSERT INTO deleted_audit VALUES( OLD.id, NOW(), count_items);
END; $$
DELIMITER ;
Related
I am creating a program which is a Car Management app in Java using Swing in Netbeans, and as the database I am using Mysql, which will do all the CRUD operation. I have created a database with 3 different tables.
DATABASE SCHEMA
CREATE TABLE car_make(
make_id INT NOT NULL AUTO_INCREMENT
make VARCHAR(50)
PRIMARY KEY(make_id)
)
CREATE TABLE car_model(
model_id INT NOT NULL AUTO_INCREMENT
model VARCHAR(50)
fk_make_id INT
PRIMARY KEY(model_id)
FOREIGN KEY(fk_make_id) REFERENCES car_make(make_id)
)
CREATE TABLE car_attributes(
car_attr_id INT NOT NULL AUTO_INCREMENT
fk_make_id INT
fk_model_id INT
year INT
body_type VARCHAR(50)
mileage INT
price DECIMAL(6,2)
PRIMARY KEY(car_attr_id )
FOREIGN KEY(fk_make_id) REFERENCES car_make(make_id)
FOREIGN KEY(fk_model_id) REFERENCES car_model(model_id )
);
The car_make table is already populated with all the car makes which I inserted manually and their ID's were auto generated. And the car_model table is also populated with different models for each make.
I have also created the user interface in netbeans using Java Swing, where the user selects the make of the car which will automatically generate the corresponding model, the year, mileage and so on and insert all that data into the car_attribute tables. My question is, what is the query to insert the car make and model into the car_attribute table as foreign keys. For example if the user chooses as Make-BMW and Model-5 Series, I want to insert both of those IDS into the third table.
this scenario came up when you want to add new car, so the GUI show you the CAR_MAKEs
when you choose, it will show you CAR_MODELs, then you need to STORE the ID of fetched data (car_makes OR car_models) in arrayList and use it in the query when the USER submit
Just pseudo code
int carMakesSelectedIndex = comboCarMakes.getSelectedIndex();
int carModelsSelectedIndex = comboCarModels.getSelectedIndex();
PreparedStatement stmt=con.prepareStatement("insert into car_attributes values(?,?,?,?,?,?,?,?,?,?)");
stmt.setInt(1,carAttribute);
stmt.setInt(2,carMakesIdList.get( carMakesSelectedIndex ) );
stmt.setInt(3,carMakesIdList.get( carModelsSelectedIndex ) );
stmt.setString(4,carYear );
// the same with other attribute
I am very new to sql, and I am trying to delete a row of person data from a BANK_PERSON table along with its FK constraints. I am using JDBC to declare a callable statement, which takes in a username, then calls a stored procedure in sql and deletes a person from the database.I know the basic process for creating a stored procedure, but I'm not sure how to do it in my case . Here is my BANK_PERSON table and MY BANK_ACCOUNT table with an FK constraint.
CREATE TABLE BANK_PERSON (
ID_NUMBER INTEGER PRIMARY KEY,
FIRSTNAME VARCHAR2(30),
LASTNAME VARCHAR2(30),
USERNAME VARCHAR2(30),
PASS VARCHAR2(30),
RANK INTEGER
);
CREATE TABLE BANK_ACCOUNT (
ACCOUNT_NUMBER INTEGER PRIMARY KEY,
ACCOUNT_BALANCE NUMBER(10,2),
FOREIGN KEY(ACCOUNT_NUMBER) REFERENCES BANK_PERSON(ID_NUMBER));
First of all I suggest to use ON DELETE CASCADE option for your FK which allows you delete all child entries automatically. In other words use following script for creation of BANK_ACCOUNT table:
CREATE TABLE BANK_ACCOUNT (
ACCOUNT_NUMBER INTEGER PRIMARY KEY,
ACCOUNT_BALANCE NUMBER(10,2),
FOREIGN KEY(ACCOUNT_NUMBER) REFERENCES A1(ID_NUMBER) ON DELETE CASCADE);
Then use following script for procedure creation:
CREATE OR REPLACE
PROCEDURE DELETE_PERSON
(USERNAME IN VARCHAR2) AS
BEGIN
delete from BANK_PERSON where BANK_PERSON.USERNAME like DELETE_PERSON.USERNAME;
END DELETE_PERSON;
And finally call of newly created procedure:
EXECUTE DELETE_PERSON('Marcus');
Hope this is what you would like to get.
Using MySQL, I have the following SQL Table definition:
CREATE TABLE books (
author INT,
book INT,
name VARCHAR(128),
PRIMARY KEY(author, book)
);
What I want is that I have an Id for author that I set manually and an Id for book that is incremented for each author id. Therefore I created a trigger like so:
CREATE TRIGGER trBooks
BEFORE INSERT ON books
FOR EACH ROW SET NEW.book = (
SELECT COALESCE(MAX(book), -1) + 1 FROM books
WHERE author = NEW.author
);
This works fine for me. But now I need to know the book id that was set for my inserted entry that I inserted in Java. Something like the Insert with Output as in MSSQL or a Statement.executeQuery("INSERT ..."). The solution has to be thread safe, so a separate INSERT and SELECT is no good solution, since there might have been another INSERT in the meantime.
Thanks for your help!
Your data model just doesn't make sense. You have two entities, "books" and "authors". These should each be represented as a table. Because a book can have multiple authors and an author can write multiple books, you want a junction table.
This looks like this:
CREATE TABLE Books (
BookId INT auto_increment primary key,
Title VARCHAR(255)
);
CREATE TABLE Authors (
AuthorId INT auto_increment primary key,
Name VARCHAR(255)
);
CREATE TABLE BookAuthors (
BookAuthorId INT auto_increment primary key,
AuthorId INT,
BookId INT,
CONSTRAINT fk_BookAuthor_BookId FOREIGN KEY (BookId) REFERENCES Books(BookId),
CONSTRAINT fk_BookAuthor_AuthorId FOREIGN KEY (BookId) REFERENCES Authors(AuthorId),
UNIQUE (AuthorId, BookId)
);
As for your question about inserts. You don't need a trigger to set auto-incremented ids. You can use LAST_INSERT_ID() to fetch the most recent inserted value.
If you have an insert with an ON DUPLICATE KEY clause, and there is a duplicate key, is there any way to get back the primary key that was duplicated? or do I have to do my own manual query? As far as I can tell getGeneratedKeys() from the CallableStatement class will not return as a new insert wasn't actually done.
EDIT
Sorry if it wasn't clear but I want to get the PRIMARY KEY of the record back.
So if I were have the following table (excuse syntax, just typing it freehand):
CREATE TABLE some_table(
id int(11) unsigned NOT NULL AUTO_INCREMENT,
value varchar(500)NOT NULL,
count int(10) unsigned NOT NULL DEFAULT '0',
PRIMARY KEY (id),
UNIQUE KEY (value)
);
INSERT INTO some_table(value) ON DUPLICATE KEY UPDATE count = count + 1;
If I were to add 'test' as the value, a new record would be added and the id would be returned by getGeneratedKeys();
If I were to attempt to add 'test' again, the key already exists and therefore the count would be updated. What I want is the primary key/id of that row which was updated. Do I have to see that I get no results back from getGeneratedKeys() - as none where generated - and do another select after the fact?
ON DUPLICATE KEY UPDATE count = count + 1, id = LAST_INSERT_ID(id)
Note: This shouldn't be necessary as of MySQL 5.5.
i have two tables where in the first one i have 14 millions and in the second one i have 1.5 million of data.
So i wonder how could i transfer this data to another table to be normalized ?
And how do i convert some type to another, for example: i have a field called 'year' but its type is varchar, but i want it an integer instead, how do i do that ?
I thought about do this using JDBC in a loop while from java, but i think this is not effeciently.
// 1.5 million of data
CREATE TABLE dbo.directorsmovies
(
movieid INT NULL,
directorid INT NULL,
dname VARCHAR (500) NULL,
addition VARCHAR (1000) NULL
)
//14 million of data
CREATE TABLE dbo.movies
(
movieid VARCHAR (20) NULL,
title VARCHAR (400) NULL,
mvyear VARCHAR (100) NULL,
actorid VARCHAR (20) NULL,
actorname VARCHAR (250) NULL,
sex CHAR (1) NULL,
as_character VARCHAR (1500) NULL,
languages VARCHAR (1500) NULL,
genres VARCHAR (100) NULL
)
And this is my new tables:
DROP TABLE actor
CREATE TABLE actor (
id INT PRIMARY KEY IDENTITY,
name VARCHAR(200) NOT NULL,
sex VARCHAR(1) NOT NULL
)
DROP TABLE actor_character
CREATE TABLE actor_character(
id INT PRIMARY KEY IDENTITY,
character VARCHAR(100)
)
DROP TABLE director
CREATE TABLE director(
id INT PRIMARY KEY IDENTITY,
name VARCHAR(200) NOT NULL,
addition VARCHAR(150)
)
DROP TABLE movie
CREATE TABLE movie(
id INT PRIMARY KEY IDENTITY,
title VARCHAR(200) NOT NULL,
year INT
)
DROP TABLE language
CREATE TABLE language(
id INT PRIMARY KEY IDENTITY,
language VARCHAR (100) NOT NULL
)
DROP TABLE genre
CREATE TABLE genre(
id INT PRIMARY KEY IDENTITY,
genre VARCHAR(100) NOT NULL
)
DROP TABLE director_movie
CREATE TABLE director_movie(
idDirector INT,
idMovie INT,
CONSTRAINT fk_director_movie_1 FOREIGN KEY (idDirector) REFERENCES director(id),
CONSTRAINT fk_director_movie_2 FOREIGN KEY (idMovie) REFERENCES movie(id),
CONSTRAINT pk_director_movie PRIMARY KEY(idDirector,idMovie)
)
DROP TABLE genre_movie
CREATE TABLE genre_movie(
idGenre INT,
idMovie INT,
CONSTRAINT fk_genre_movie_1 FOREIGN KEY (idMovie) REFERENCES movie(id),
CONSTRAINT fk_genre_movie_2 FOREIGN KEY (idGenre) REFERENCES genre(id),
CONSTRAINT pk_genre_movie PRIMARY KEY (idMovie, idGenre)
)
DROP TABLE language_movie
CREATE TABLE language_movie(
idLanguage INT,
idMovie INT,
CONSTRAINT fk_language_movie_1 FOREIGN KEY (idLanguage) REFERENCES language(id),
CONSTRAINT fk_language_movie_2 FOREIGN KEY (idMovie) REFERENCES movie(id),
CONSTRAINT pk_language_movie PRIMARY KEY (idLanguage, idMovie)
)
DROP TABLE movie_actor
CREATE TABLE movie_actor(
idMovie INT,
idActor INT,
CONSTRAINT fk_movie_actor_1 FOREIGN KEY (idMovie) REFERENCES movie(id),
CONSTRAINT fk_movie_actor_2 FOREIGN KEY (idActor) REFERENCES actor(id),
CONSTRAINT pk_movie_actor PRIMARY KEY (idMovie,idActor)
)
UPDATE:
I'm using SQL Server 2008.
Sorry guys i forgot to mention that are different databases :
The not normalized is call disciplinedb and the my normalized call imdb.
Best regards,
Valter Henrique.
If both tables are in the same database, then the most efficient transfer is to do it all within the database, preferably by sending a SQL statement to be executed there.
Any movement of data from the d/b server to somewhere else and then back to the d/b server is to be avoided unless there is a reason it can only be transformed off-server. If the destination is different server, then this is much less of an issue.
Though my tables were dwarfs compared to yours, I got over this kind of problem once with stored procedures. For MySQL, below is a simplified (and untested) essence of my script, but something similar should work with all major SQL bases.
First you should just add a new integer year column (int_year in example) and then iterate over all rows using the procedure below:
DROP PROCEDURE IF EXISTS move_data;
CREATE PROCEDURE move_data()
BEGIN
DECLARE done INT DEFAULT 0;
DECLARE orig_id INT DEFAULT 0;
DECLARE orig_year VARCHAR DEFAULT "";
DECLARE cur1 CURSOR FOR SELECT id, year FROM table1;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cur1;
PREPARE stmt FROM "UPDATE table1 SET int_year = ? WHERE id = ?";
read_loop: LOOP
FETCH cur1 INTO orig_id, orig_year;
IF done THEN
LEAVE read_loop;
END IF;
SET #year= orig_year;
SET #id = orig_id;
EXECUTE stmt USING #orig_year, #id;
END LOOP;
CLOSE cur1;
END;
And to start the procedure, just CALL move_data().
The above SQL has two major ideas to speed it up:
Use CURSORS to iterate over a large table
Use PREPARED statement to quickly execute pre-known commands
PS. for my case this speeded things up from ages to seconds, though in your case it can still take a considerable amount of time. So it would be probably best to execute from command line, not some web interface (e.g. PhpMyAdmin).
I just recently did this for ~150 Gb of data. I used a pair of merge statements for each table. The first merge statement said "if it's not in the destination table, copy it there" and the second said "if it's in the destination table, delete it from the source". I put both in a while loop and only did 10000 rows in each operation at a time. Keeping it on the server (and not transferring it through a client) is going to be a huge boon for performance. Give it a shot!