SQL queries. DML (Data Manipulation Language) - Relational databases - Database - Каталог статей

SQL queries. DML (Data Manipulation Language)

11.4.2.4 describe the basic SQL queries for working with one table in a database: SELECT, UPDATE, INSERT and DELETE

11.4.2.5 use SQL SELECT for data selection in more tables

SQL queries. Data Manipulation Language.

Data Manipulation Language (DML) is a computer language including commands permitting users to manipulate data in a database.

The SQL SELECT Statement

The SELECT statement is used to select data from a database.

Syntax	Example
SELECT column1, column2, ... FROM table_name;	SELECT surname, firstname FROM users;
SELECT column1, column2, ... FROM table_name WHERE condition;	SELECT surname, firstname, iin FROM users WHERE userID=5;

The SQL INSERT Statement

The INSERT command is used to enter records into a table. Values are entered to the table corresponding order to the listed columns.

Syntax	Example
INSERT INTO tablename (field1, field2, ...) VALUES ('value1', 'value2', ...);	INSERT INTO users (surname, firstname, address, age) VALUES ('Aliyev', 'Ruslan', 'Konaev dist. 7-15', 15);
INSERT INTO tablename VALUES ('value1', 'value2', ...);	INSERT INTO users VALUES (userID, 'Aliyev', 'Ruslan', 'Konaev dist. 7-15', 15);

SQL UPDATE Statement

The UPDATE statement is used to modify the existing records in a table.

Syntax	Example
UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;	UPDATE users SET surname = "Makeev", firstname = "Maksim" WHERE userID = 67;