Oracle Database Data Management
1. Data Definition Language (DDL)
Data Definition Language (DDL) is used to define the database schema. It includes commands like CREATE, ALTER, and DROP, which are used to create, modify, and delete database objects such as tables, indexes, and views.
Example: Think of DDL as the blueprint for a house. Just as a blueprint defines the structure of a house, DDL defines the structure of database objects.
2. Data Manipulation Language (DML)
Data Manipulation Language (DML) is used to manipulate data within database objects. It includes commands like SELECT, INSERT, UPDATE, and DELETE, which are used to retrieve, add, modify, and remove data from tables.
Example: Consider DML as the actions you take in a house. Just as you add furniture, rearrange items, and remove clutter, DML adds, modifies, and removes data in the database.
3. Data Control Language (DCL)
Data Control Language (DCL) is used to control access to the database. It includes commands like GRANT and REVOKE, which are used to grant and revoke privileges to users and roles.
Example: Think of DCL as the security system for a house. Just as you grant or revoke access to different areas of the house, DCL grants or revokes access to database objects.
4. Transaction Control Language (TCL)
Transaction Control Language (TCL) is used to manage transactions in the database. It includes commands like COMMIT, ROLLBACK, and SAVEPOINT, which are used to commit changes, roll back to a previous state, and set savepoints within a transaction.
Example: Consider TCL as the undo/redo function in a word processor. Just as you can undo changes or save your progress, TCL allows you to manage changes in the database.
5. Indexes
Indexes are database objects that improve the speed of data retrieval operations on tables. They are similar to the index in a book, which allows you to quickly find information without reading the entire book.
Example: Think of indexes as the table of contents in a book. Just as the table of contents helps you find specific chapters quickly, indexes help you find specific data in a table quickly.
6. Views
Views are virtual tables that represent data from one or more tables. They provide a way to simplify complex queries and control access to data by showing only the necessary columns and rows.
Example: Consider views as a summary report. Just as a summary report condenses information from multiple sources, views condense data from multiple tables.
7. Sequences
Sequences are database objects that generate unique numbers. They are often used to create primary keys that are automatically incremented with each new row.
Example: Think of sequences as a ticket counter at a movie theater. Just as the ticket counter generates unique ticket numbers, sequences generate unique numbers for database rows.
8. Synonyms
Synonyms are database objects that provide an alternative name for another object. They simplify access to objects by allowing you to use a shorter or more meaningful name.
Example: Consider synonyms as nicknames. Just as a nickname is a shorter or more familiar name for a person, a synonym is a shorter or more meaningful name for a database object.
9. Materialized Views
Materialized views are precomputed views that store the results of a query in a table. They improve query performance by reducing the need to recompute the results each time the view is accessed.
Example: Think of materialized views as a cache. Just as a cache stores frequently accessed data to improve performance, materialized views store query results to improve performance.
10. Partitioning
Partitioning is a technique that divides large tables into smaller, more manageable pieces called partitions. It improves performance and manageability by allowing you to work with smaller subsets of data.
Example: Consider partitioning as organizing a large library into smaller sections. Just as smaller sections make it easier to find books, partitions make it easier to manage large tables.
11. Data Integrity
Data integrity refers to the accuracy and consistency of data in a database. It is maintained through constraints such as PRIMARY KEY, FOREIGN KEY, UNIQUE, and CHECK, which enforce rules on the data.
Example: Think of data integrity as the rules of a game. Just as the rules ensure fair play, constraints ensure accurate and consistent data in the database.