Download Creando una base de datos

Bases de Datos 1
Prof. Daniel Obando Fuentes
CREANDO UNA BASE DE DATOS
CREATE DATABASE dbname;
ENCODINGS
•Character encoding: Es un repertorio de
caracteres que permiten representar un
determinado lenguaje.
•Tambien llamados character set, character map
o codeset.
•Cada caracter puede contener una cantidad
diferente de bytes, permitiendo asi ampliar el
rango de caracteres a representar.
ENCODINGS
•US-ASCII, code unit 7 bits.
•UTF-8, code unit 8 bits.
•EBCDIC, code unit 8 bits.
•UTF-16, code unit 16 bits.
•UTF-32, code unit 32 bits.
CHARSETS Y COLLATIONS
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A character set is a set of symbols and encodings. A collation is a set of rules for
comparing characters in a character set. Let's make the distinction clear with an
example of an imaginary character set.
Suppose that we have an alphabet with four letters: “A”, “B”, “a”, “b”. We give each
letter a number: “A” = 0, “B” = 1, “a” = 2, “b” = 3. The letter “A” is a symbol, the
number 0 is the encoding for “A”, and the combination of all four letters and their
encodings is a character set.
Suppose that we want to compare two string values, “A” and “B”. The simplest way
to do this is to look at the encodings: 0 for “A” and 1 for “B”. Because 0 is less than
1, we say “A” is less than “B”. What we've just done is apply a collation to our
character set. The collation is a set of rules (only one rule in this case): “compare
the encodings.” We call this simplest of all possible collations a binary collation.
But what if we want to say that the lowercase and uppercase letters are
equivalent? Then we would have at least two rules: (1) treat the lowercase letters
“a” and “b” as equivalent to “A” and “B”; (2) then compare the encodings. We call
this a case-insensitive collation. It is a little more complex than a binary collation.
CHARSETS Y COLLATIONS
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In real life, most character sets have many characters: not
just “A” and “B” but whole alphabets, sometimes multiple
alphabets or eastern writing systems with thousands of
characters, along with many special symbols and
punctuation marks. Also in real life, most collations have
many rules, not just for whether to distinguish lettercase,
but also for whether to distinguish accents (an “accent” is
a mark attached to a character as in German “Ö”), and for
multiple-character mappings (such as the rule that “Ö” =
“OE” in one of the two German collations).
CUAL ES EL MEJOR ENCODING?

Depende

UTF8 soporta la mayoría de lenguajes
occidentales y versiones simplificadas
de lenguajes orientales.
 Unicode para Mandarin
ALTER DATABASE
ALTER DATABASE databasename
CHARACTER SET utf8
COLLATE utf8_unicode_ci;
CREATE TABLE
CREATE TABLE table_name
(
column_name1 data_type(size),
column_name2 data_type(size),
column_name3 data_type(size),
....
);
ALTER TABLE
ALTER TABLE tablename
CONVERT TO CHARACTER SET utf8
COLLATE utf8_unicode_ci;
PERSONS
CREATE TABLE Persons
(
PersonID int,
LastName varchar(255),
FirstName varchar(255),
Address varchar(255),
City varchar(255)
);
DROP
• DROP TABLE table_name
• /* limpiar */
• TRUNCATE TABLE table_name
• DROP DATABASE database_name
CONSTRAINTS
CREATE TABLE table_name
(
column_name1 data_type(size) constraint_name,
column_name2 data_type(size) constraint_name,
column_name3 data_type(size) constraint_name,
....
);
CONSTRAINTS
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NOT NULL – Indicates that a column cannot store NULL value
UNIQUE - Ensures that each row for a column must have a unique
value
PRIMARY KEY - A combination of a NOT NULL and UNIQUE. Ensures
that a column (or combination of two or more columns) have an
unique identity which helps to find a particular record in a table more
easily and quickly
FOREIGN KEY - Ensure the referential integrity of the data in one table
to match values in another table
CHECK - Ensures that the value in a column meets a specific condition
DEFAULT - Specifies a default value when specified none for this
column
NOT NULL
CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)
UNIQUE
CREATE TABLE Persons
(
P_Id int NOT NULL UNIQUE,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)
UNIQUE (COMPAT)
CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CONSTRAINT uc_PersonID UNIQUE (P_Id,LastName)
)
UNIQUE CON ALTER
ALTER TABLE Persons
ADD CONSTRAINT uc_PersonID UNIQUE (P_Id,LastName)
PRIMARY KEY
CREATE TABLE Persons
(
P_Id int NOT NULL PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)
PRIMARY KEY (COMPAT)
CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)
)
PK CON ALTER
ALTER TABLE Persons
ADD PRIMARY KEY (P_Id)
FOREIGN KEY
CREATE TABLE Orders
(
O_Id int NOT NULL PRIMARY KEY,
OrderNo int NOT NULL,
P_Id int FOREIGN KEY REFERENCES
Persons(P_Id)
)
FOREIGN KEY (COMPAT)
CREATE TABLE Orders
(
O_Id int NOT NULL,
OrderNo int NOT NULL,
P_Id int,
PRIMARY KEY (O_Id),
CONSTRAINT fk_PerOrders FOREIGN KEY (P_Id)
REFERENCES Persons(P_Id)
)
FK CON ALTER
ALTER TABLE Orders
ADD CONSTRAINT fk_PerOrders
FOREIGN KEY (P_Id)
REFERENCES Persons(P_Id)
CHECK
CREATE TABLE Persons
(
P_Id int NOT NULL CHECK (P_Id>0),
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)
CHECK (COMPAT)
CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CONSTRAINT chk_Person CHECK (P_Id>0 AND City='Sandnes')
)
CHECK CON ALTER
ALTER TABLE Persons
ADD CONSTRAINT chk_Person CHECK
(P_Id>0 AND City='Sandnes')
DEFAULT
CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255) DEFAULT 'Sandnes'
)
CREATE TABLE Orders
(
O_Id int NOT NULL,
OrderNo int NOT NULL,
P_Id int,
OrderDate date DEFAULT GETDATE()
)
DEFAULT (COMPAT)
CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CONSTRAINT chk_Person CHECK (P_Id>0 AND City='Sandnes')
)
DEFAULT CON ALTER
ALTER TABLE Persons
ALTER COLUMN City SET DEFAULT 'SANDNES'
DROPPING
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ALTER TABLE Persons DROP CONSTRAINT uc_PersonID
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ALTER TABLE Persons DROP CONSTRAINT pk_PersonID
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ALTER TABLE Orders DROP CONSTRAINT fk_PerOrders
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ALTER TABLE Persons DROP CONSTRAINT chk_Person
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ALTER TABLE Persons ALTER COLUMN City DROP DEFAULT
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DROP DATABASE Olympics;
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DROP TABLE sport;
EJERCICIO
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Cree un script que genere la siguiente base de datos para
el diagrama ER de OlympicsData
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UTF8 charset y collation
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Cree los primary keys y los foreign keys
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Cree las tablas intermedias
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Utilice donde corresponda:
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Default
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Not null
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Check
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Unique
REFERENCIAS
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http://dev.mysql.com/doc/refman/5.0/en/charset-general.html
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http://www.w3schools.com/sql/
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http://msdn.microsoft.com/en-us/library/ms176061.aspx
TAREA: INVESTIGACIÓN
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Cómo conectarse a una base de datos
SQL Server desde Java
Envíe un script de ejemplo
SQL SERVER 2014
• Por default UTF-8
• Para soportar UNICODE se usa UTF-16. Para usar UTF-16
• Usar tipos nchar, nvarchar, ntext
• Usar collations que tengan _CS
• CREATE DATABASE MyOptionsTest
COLLATE Latin1_General_100_CS_AS_SC;