Data Query Language (DQL) is a subset of SQL commands used primarily to query and retrieve data from existing database tables. In SQL, DQL is mostly centered around theSELECTstatement, which is used to fetch data according to specified criteria. Here’s an overview of theSELECTstatement and ...
SQL Copy Example SELECT FirstName, LastName, Salary FROM Employees WHERE Salary > 50000 ORDER BY Salary DESC; SQL Copy 3. UPDATE The UPDATE command modifies existing records in a table. Syntax UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition; SQL Copy Exampl...
INSERTINTOcustomers(customer_id,customer_name,email)VALUES(101,'Alice','alice@example.com'),(102,'Bob','bob@example.com'),(103,'Charlie','charlie@example.com'); 上述SQL 查询一次性插入了多个客户记录,而不是多次单独插入,以减少通信开销。 3.子查询:子查询是嵌套在其他查询内部的查询,可用于根据...
CREATE Command in SQL SQL Create the database or its object (ie table, index, view, function, etc.). Syntax CREATE DATABASE databasename Example CREATE DATABASE Student_data; SQL Copy Syntax CREATE TABLE table_name ( column1 datatype, column2 datatype, column3 datatype, ... ); Examp...
插入数据是向数据库表中添加新记录的操作。为此,我们使用INSERT INTO语句,指定要插入数据的表以及要插入的值。以下是一个基本的插入数据的SQL语句示例: INSERT INTO customers (customer_name, contact_email, phone_number)VALUES ('John Doe', 'john.doe@example.com', '+1-123-456-7890'); ...
Data manipulation Language (DML) is a set of statements that help manipulate data in the database. The heart of the DML is T-SQL. A number of enhancements have been made to T-SQL in the Yukon version. In this section we shall examine some of the new statements that have been introdu...
However when in a Table, for example, Table1 with the Fields: Id (Autogenerated Primary Key), Field2 and Field3 when executing the lower instruction shows an Error: INSERT INTO Table1 VALUES (Data_Campo2, Data_Country3); The mistake is: ...
数据操作语言(DML)是SQL(结构化查询语言)的一部分,用于管理数据库中的数据。DML语句允许用户执行以下操作: 插入数据(INSERT):将新记录添加到数据库表中。 更新数据(UPDATE):修改现有记录的值。 删除数据(DELETE):从表中移除记录。 查询数据(SELECT):从表中检索数据。
1. Overview InSQL, different types of commands are categorized based on their functionality. These categories include Data Definition Language (DDL), Data Manipulation Language (DML), Data Control Language (DCL), and Transaction Control Language (TCL). Additionally, understanding these categories helps...
Data Definition Language (DDL): Definition & Example 6:03 Data Manipulation Language (DML): Definition & Example DDL, DML & DCL in MySQL | Definition & History 4:14 4:36 Next Lesson Data Definition Language (DDL) Commands Data Manipulation Language (DML) Commands 3:39 SQL DROP Co...