毕业设计软件开发网站开发,网站维护建设招标,百度广告点击软件,网站建设费入如保入账SQL#xff08;Structured Query Language#xff09;是一种用于存储、操作和检索数据库中数据的标准编程语言。以下是一些常用的 SQL 语法#xff1a; 数据库操作 创建数据库#xff1a;CREATE DATABASE database_name;删除数据库#xff1a;DROP DATABASE database_name…SQLStructured Query Language是一种用于存储、操作和检索数据库中数据的标准编程语言。以下是一些常用的 SQL 语法 数据库操作 创建数据库CREATE DATABASE database_name;删除数据库DROP DATABASE database_name;选择数据库USE database_name; 表操作 创建表CREATE TABLE table_name (column1 datatype, column2 datatype, ...);删除表DROP TABLE table_name;修改表结构ALTER TABLE table_name ADD column_name datatype;删除表中的列ALTER TABLE table_name DROP COLUMN column_name; 数据操作 插入数据INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...);更新数据UPDATE table_name SET column1 value1, column2 value2 WHERE condition;删除数据DELETE FROM table_name WHERE condition;查询数据SELECT column1, column2, ... FROM table_name WHERE condition; 条件查询 等于SELECT * FROM table_name WHERE column value;不等于SELECT * FROM table_name WHERE column ! value;大于SELECT * FROM table_name WHERE column value;大于等于SELECT * FROM table_name WHERE column value;小于SELECT * FROM table_name WHERE column value;小于等于SELECT * FROM table_name WHERE column value;BETWEENSELECT * FROM table_name WHERE column BETWEEN value1 AND value2;LIKE模糊查询SELECT * FROM table_name WHERE column LIKE value%;INSELECT * FROM table_name WHERE column IN (value1, value2, ...);AND/ORSELECT * FROM table_name WHERE column1 value1 AND column2 value2; 聚合函数 COUNTSELECT COUNT(*) FROM table_name;SUMSELECT SUM(column) FROM table_name;AVGSELECT AVG(column) FROM table_name;MAXSELECT MAX(column) FROM table_name;MINSELECT MIN(column) FROM table_name; 分组和排序 分组SELECT column1, COUNT(*) FROM table_name GROUP BY column1;排序SELECT * FROM table_name ORDER BY column1 ASC, column2 DESC; 连接查询 内连接INNER JOINSELECT * FROM table1 INNER JOIN table2 ON table1.column_name table2.column_name;左连接LEFT JOINSELECT * FROM table1 LEFT JOIN table2 ON table1.column_name table2.column_name;右连接RIGHT JOINSELECT * FROM table1 RIGHT JOIN table2 ON table1.column_name table2.column_name;全连接FULL JOIN注意并非所有数据库系统都支持 FULL JOINSELECT * FROM table1 FULL JOIN table2 ON table1.column_name table2.column_name; 子查询 嵌套查询SELECT * FROM table_name WHERE column IN (SELECT column FROM other_table WHERE condition); 事务控制 开启事务BEGIN TRANSACTION;提交事务COMMIT;回滚事务ROLLBACK; 权限控制 授予权限GRANT SELECT, INSERT ON table_name TO user_name;撤销权限REVOKE SELECT, INSERT ON table_name FROM user_name;
