Oracle DDL

1、Creating a Table With SQL

Creating a Simple Table Using SQL

-- create a simple table for keeping track of birthdays

CREATE TABLE my_birthdays
  ( first_name     VARCHAR2(20),
    last_name      VARCHAR2(25),
    bday_date      DATE
  ); 

Creating a Table With NOT NULL Constraints Using SQL

-- create a table with NOT NULL constraints in the HR schema

CREATE TABLE personal_info (
    employee_id         NUMBER(6,0) NOT NULL,
    birth_date          DATE NOT NULL,
    social_security_id  VARCHAR2(12) NOT NULL,
    marital_status      VARCHAR2(10),
    dependents_claimed  NUMBER(2,0) DEFAULT 1,
    contact_name        VARCHAR2(45) NOT NULL,
    contact_phone       VARCHAR2(20) NOT NULL,
    contact_address     VARCHAR2(80) NOT NULL
);

 
2、Adding, Altering, and Dropping a Table Column With SQL

Adding, Altering, and Dropping a Table Column Using SQL

-- add a new column

ALTER TABLE personal_info ADD
(contact_email VARCHAR2(30) NULL);

-- modify a column

ALTER TABLE personal_info MODIFY
(contact_email VARCHAR2(40) NOT NULL);

-- drop a column

ALTER TABLE personal_info DROP COLUMN
contact_address;

 3、Creating and Altering a Constraint With SQL

Creating, Altering, and Dropping Constraints Using SQL

-- add a primary key constraint 

ALTER TABLE personal_info 
  ADD CONSTRAINT personal_info_pkey 
  PRIMARY KEY (employee_id);

-- add a foreign key constraint

ALTER TABLE personal_info 
  ADD CONSTRAINT personal_info_fkey 
  FOREIGN KEY (employee_id) REFERENCES employees (employee_id) 
  ON DELETE CASCADE;

-- add a unique constraint

ALTER TABLE personal_info 
  ADD CONSTRAINT personal_info_unique_con 
  UNIQUE (social_security_id);

-- add a check constraint

ALTER TABLE personal_info 
  ADD CONSTRAINT personal_info_check_con 
  CHECK ( dependents_claimed > 0);

-- disable a constraint

ALTER TABLE personal_info 
  DISABLE CONSTRAINT personal_info_check_con;

-- enable a constraint

ALTER TABLE personal_info 
  ENABLE CONSTRAINT personal_info_check_con;

-- drop a constraint

ALTER TABLE personal_info 
  DROP CONSTRAINT personal_info_check_con;

4、Renaming a Table With SQL

Renaming a Table Using SQL

-- rename the my_birthdays table

ALTER TABLE my_birthdays RENAME to birthdays;

5、Renaming a Table With SQL

Dropping a Table Using SQL

-- drop tables from the database

-- use caution when use the DROP statement!

DROP TABLE birthdays;
DROP TABLE personal_info;

6、Creating, Altering, and Dropping an Index With SQL

Creating, Modifying, and Dropping an Index Using SQL

-- create an index on a single column to make queries faster on that column

CREATE INDEX emp_hiredate_idx ON employees (hire_date);

-- rename the index

ALTER INDEX emp_hiredate_idx 
  RENAME TO emp_hire_date_idx;

-- drop the index

DROP INDEX emp_hire_date_idx;

-- create an index on two columns to make queries faster on the first column

-- or both columns

CREATE INDEX emp_mgr_id_ix ON employees (employee_id, manager_id);
DROP INDEX emp_mgr_id_ix;

-- a function-based index precalculates the result and speeds up queries that

-- use the function for searching or sorting, in this case UPPER(last_name)

CREATE INDEX emp_upper_last_name_ix ON employees (UPPER(last_name));
DROP INDEX emp_upper_last_name_ix;

7、Creating, Altering, and Dropping an Index With SQL

Creating a View Using SQL

-- create a view to display data from departments and employees

CREATE OR REPLACE VIEW my_emp_view AS
SELECT d.department_id, d.department_name, d.manager_id,
  e.employee_id, e.first_name, e.last_name 
  FROM employees e, departments d 
  WHERE d.manager_id = e.employee_id;

Dropping a View Using SQL

-- drop the view with the DROP VIEW statement

DROP VIEW my_emp_view;

8、Creating and Dropping a Sequence With SQL

Creating a Sequence Using SQL

-- create a new sequence to use with the employees table

-- this sequence starts at 1000 and increments by 1

CREATE SEQUENCE new_employees_seq START WITH 1000 INCREMENT BY 1;

-- to use the sequence, first initialize the sequence with NEXTVAL

SELECT new_employees_seq.NEXTVAL FROM DUAL;

-- after initializing the sequence, use CURRVAL as the next value in the sequence

INSERT INTO employees VALUES 
  (new_employees_seq.CURRVAL, 'Pilar', 'Valdivia', 'pilar.valdivia',
  '555.111.3333', '01-SEP-05', 'AC_MGR', 9100, .1, 101, 110);

-- query the employees table to check the current value of the sequence

-- which was inserted used as employee_id in the previous INSERT statement

SELECT employee_id, last_name FROM employees WHERE last_name = 'Valdivia';

Dropping a Sequence Using SQL

-- drop the sequence

DROP SEQUENCE new_employees_seq;

9、Creating and Dropping a Synonym With SQL

Creating a Synonym Using SQL

-- create a synonym for the employees table

CREATE SYNONYM emps for HR.employees;

-- query the employees table using the emps synonym

SELECT employee_id, last_name FROM emps WHERE employee_id < 105;

Dropping a Synonym Using SQL

-- drop the synonym

DROP SYNONYM emps;