Selecting Categories That Contain Product

    
SQL>
SQL>
SQL> CREATE TABLE ProductCategory (
  2  ProductID INT NOT NULL,
  3  CategoryID INT NOT NULL,
  4  PRIMARY KEY (ProductID, CategoryID)
  5  );

Table created.

SQL>
SQL>
SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (1,3);

1 row created.

SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (2,1);

1 row created.

SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (2,3);

1 row created.

SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (3,3);

1 row created.

SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (4,1);

1 row created.

SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (5,2);

1 row created.

SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (6,3);

1 row created.

SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (6,4);

1 row created.

SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (7,4);

1 row created.

SQL> INSERT INTO ProductCategory (ProductID, CategoryID) VALUES (8,5);

1 row created.

SQL>
SQL>
SQL> CREATE TABLE Category (
  2  CategoryID INT NOT NULL PRIMARY KEY,
  3  DepartmentID INT NOT NULL,
  4  Name VARCHAR(50) NOT NULL,
  5  Description VARCHAR (200) NULL);

Table created.

SQL>
SQL> CREATE SEQUENCE CategoryIDSeq;

Sequence created.

SQL>
SQL> CREATE OR REPLACE TRIGGER CategoryAutonumberTrigger
  2  BEFORE INSERT ON Category
  3  FOR EACH ROW
  4  BEGIN
  5     SELECT CategoryIDSeq.NEXTVAL
  6     INTO :NEW.CategoryID FROM DUAL;
  7  END;
  8  /

Trigger created.

SQL> INSERT INTO Category (DepartmentID, Name, Description) VALUES (1, 'Local', 'In town');

1 row created.

SQL> INSERT INTO Category (DepartmentID, Name, Description) VALUES (1, 'Remote', 'Telecommute');

1 row created.

SQL> INSERT INTO Category (DepartmentID, Name, Description) VALUES (2, 'Masks', 'By bits');

1 row created.

SQL> INSERT INTO Category (DepartmentID, Name, Description) VALUES (3, 'Wireless', 'Not connected');

1 row created.

SQL> INSERT INTO Category (DepartmentID, Name, Description) VALUES (3, 'Wired', 'Connected');

1 row created.

SQL>
SQL>
SQL> SELECT Category.CategoryID, Name
  2  FROM Category INNER JOIN ProductCategory
  3  ON Category.CategoryID = ProductCategory.CategoryID
  4  AND ProductCategory.ProductID = 6;

CATEGORYID NAME
---------- --------------------------------------------------
         3 Masks
         4 Wireless

2 rows selected.

SQL>
SQL>
SQL> SELECT CategoryID, Name
  2  FROM Category
  3  WHERE CategoryID IN
  4     (SELECT CategoryID
  5      FROM ProductCategory
  6      WHERE ProductCategory.ProductID = 6);

CATEGORYID NAME
---------- --------------------------------------------------
         3 Masks
         4 Wireless

2 rows selected.

SQL>
SQL>
SQL> drop table Category;

Table dropped.

SQL> drop table ProductCategory;

Table dropped.

SQL> drop sequence CategoryIDSeq;

Sequence dropped.

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Selecting Categories That Contain Product : Select « Select Query « Oracle PL / SQL

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