SQL Statement

SQL 语句基础知识点 SQL 语句是结构化查询语言（Structured Query Language）的缩写，用于管理关系数据库管理系统（RDBMS）。SQL 语句可以创建、修改、查询和删除数据库中的数据。 一、基础语句 1. SELECT 语句：用于从数据库中选择数据。 SELECT column_name(s) FROM table_name; 2. ALTER 语句：用于修改数据库中的表结构。 ALTER TABLE table_name ADD column_name datatype; ALTER TABLE table_name DROP COLUMN column_name; 3. AS 语句：用于重命名表或列。 SELECT column_name AS column_alias FROM table_name; SELECT column_name FROM table_name AS table_alias; 二、条件语句 1. WHERE 语句：用于过滤数据。 SELECT column_name(s) FROM table_name WHERE condition; 2. AND 语句：用于连接两个条件。 SELECT column_name(s) FROM table_name WHERE condition AND condition; 3. OR 语句：用于连接两个条件。 SELECT column_name(s) FROM table_name WHERE condition OR condition; 4. BETWEEN 语句：用于选择在某个范围内的数据。 SELECT column_name(s) FROM table_name WHERE column_name BETWEEN value1 AND value2; 三、数据操作语句 1. CREATE 语句：用于创建数据库、表、索引、视图等。 CREATE DATABASE database_name; CREATE TABLE table_name (column_name1 data_type, column_name2 data_type, ...); CREATE INDEX index_name ON table_name (column_name); CREATE VIEW view_name AS SELECT column_name(s) FROM table_name WHERE condition; 2. DROP 语句：用于删除数据库、表、索引、视图等。 DROP DATABASE database_name; DROP TABLE table_name; DROP INDEX index_name ON table_name; DROP VIEW view_name; 3. INSERT 语句：用于向表中插入数据。 INSERT INTO table_name VALUES (value1, value2, value3, ....); INSERT INTO table_name (column1, column2, column3,...) VALUES (value1, value2, value3, ....); 4. UPDATE 语句：用于修改表中的数据。 UPDATE table_name SET column_name = new_value WHERE condition; 5. DELETE 语句：用于删除表中的数据。 DELETE FROM table_name WHERE some_column = some_value; 四、数据查询语句 1. GROUP BY 语句：用于对数据进行分组。 SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name; 2. HAVING 语句：用于对分组后的数据进行过滤。 SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name HAVING aggregate_function(column_name) operator value; 3. IN 语句：用于选择在某个列表中的数据。 SELECT column_name(s) FROM table_name WHERE column_name IN (value1, value2, ...); 4. INNER JOIN 语句：用于连接两个表。 SELECT column_name(s) FROM table_name1 INNER JOIN table_name2 ON table_name1.column_name = table_name2.column_name; 5. LEFT JOIN 语句：用于连接两个表。 SELECT column_name(s) FROM table_name1 LEFT JOIN table_name2 ON table_name1.column_name = table_name2.column_name; 6. RIGHT JOIN 语句：用于连接两个表。 SELECT column_name(s) FROM table_name1 RIGHT JOIN table_name2 ON table_name1.column_name = table_name2.column_name; SQL 语句是数据库管理的基础，掌握这些基础知识点是学习数据库的关键。