Database Normalization

It has to do with database design. Determines the structure of how data will be stored.

  • Data redundancy
  • Data Integrity
  • Anomaly

Data Redundancy

Copy of the actual data. It's easy when it comes to data recovery. However, it has disadvantages such as difficulty in consistent data processing, waste of storage space, and reduced data efficiency.

Data Integrity

It means maintaining accuracy and consistency throughout the lifecycle of data. In other words, it is not polluted data. This means you can use the data as it is entered.


  • Update anomaly
  • Insertion anomaly
  • Deletion anomaly

Update Anomaly

This error occurs when there is no logical consistency.

If there are two ID values of 519, Then change the 519 address, you don't know what to change.

Insertion Anomaly

Occurs when inserting data fails. Because of when a specific value as NULL.

Deletion Anomaly

When specific data is deleted, other data also deleted together.

SQL Type

Data Definition Language (DDL)

Includes the CREATE command used to create a table, and the DROP command used to drop a table.

Data Manipulation Language (DML)

The language used to store data in the database. Includes INSERT, DELETE, and UPDATE.

Data Control Language (DCL)

Includes commands related to database access rights. There are GRANT and REVOKE.

Data Query Language (DQL)

It is a command that can be query. for example SELECT.

Transaction Control Language (TCL)

Commits the work to the database(COMMIT), or there is a rollback function such as ROLLBACK.

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