SQL JOIN Join is used to combine rows from two or more tables, based on a related column between them. ex) Orders table ex) Customers table CustomerId Column in the Orders table refers to the CustomerId in the Customers table. The relationship between the two tables above is the Custome

Create user table CREATE content table Create category table Create content_category table Create role table Show database all tables Show user Columns Show content Columns Check all data from user table Check name data only from user table Insert data(name, email) in user table Check specific data(name is "KJ") from

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

Insert the missing statement to get all the columns from the Customers table. > SELECT * FROM Customers; Write a statement that will select the City column from the Customers table. > SELECT City FROM Customers; Select all the different values from the Country column in the Customers table. > SELECT DISTINCT Country FROM Customers; 중복 제거 키워드 (DISTINCT) Select all records where the City column has the value "Berlin". > SELECT * FROM Customers WHERE City = "Berlin";

Question 1: What does SQL stand for? > Structured Query Language Question 2: Which SQL statement is used to extract data from a database? > SELECT Question 3: Which SQL statement is used to update data in a database? > UPDATE Question 4: Which SQL statement is used to delete data from a database? > DELETE Question 5: Which SQL statement is used to insert new data in a database? > INSERT INTO Question 6: With SQL, how do you select a column named "Firs

SQL Introduction A database language used by relational databases. MySQL, Oracle, PostgreSQL, etc. Can send query to the database to get or insert the data. SQL requires a fixed data structure. Unlike SQL, database which the structure of data is not fixed is NoSQL. Database like MongoDB is called NoSQL. > What is Query? Question to filter data. Basic query Basic grammar required to use SQL Select Where And, Or, Not Order By Insert Into Null Val

데이터 베이스의 필요성 In-Memory 예기치 못한 상황으로부터 데이터를 보호하고, 프로그램이 종료된 상태에서도 데이터를 원하는 시간에 받아올 수 있다. File I/O > 단점: 데이터가 필요할 때마다 전체 파일을 읽어야 합니다. 파일의 크기가 커질수록 작업이 힘들고, 비효율적이어서 File I/O 방식의 큰 단점입니다. > 단점: 파일이 손상되거나 여러 개의 파일을 동시에 다뤄야 하는 등 복잡하고 데이터량이 많아질수록 데이터를 불러들이는 작업이 힘들어진다. 반면 관계형 데이터베이스에서는 여러 개의 테이블을 가질 수 있기 때문에 SQL을 활용해 데이터를 불러오기 수월합니다. (데이터 베이스는 단순하게 특정 형태의 파일, 대용량의 데이터를 저장하기 위한 목적이 아닙니다.) SQL 소개 (Structured Query Language) 데이터베이스 언어로, 주로 관계형 데이터베이스에서 사용합니다. ex) MySQL, Ora