-- 數據庫的操作
-- 鏈接數據庫
mysql -uroot -p
mysql -uroot -pmysql
-- 退出數據庫
EXIT/quit/ctrl+d
-- sql語句最後需要有分號;結尾
-- 顯示數據庫版本
SELECT VERSION();
-- 顯示時間
SELECT NOW();
-- 查看所有數據庫
SHOW DATABASES;
-- 創建數據庫
-- create database 數據庫名 charset=utf8;
CREATE DATABASE python04;
CREATE DATABASE python04new CHARSET=utf8;
-- 查看創建數據庫的語句
-- show crate database ....
SHOW CREATE DATABASE python04;
-- 查看當前使用的數據庫
SELECT DATABASE();
-- 使用數據庫
-- use 數據庫的名字
USE python04new;
-- 刪除數據庫
-- drop database 數據庫名;
DROP DATABASE python04;
-- 數據表的操作
-- 查看當前數據庫中所有表
SHOW TABLES;
-- 創建表
-- auto_increment表示自動增長
-- not null 表示不能爲空
-- primary key 表示主鍵
-- default 默認值
-- create table 數據表名字 (字段 類型 約束[, 字段 類型 約束]);
CREATE TABLE xxxxx(id INT, NAME VARCHAR(30));
CREATE TABLE yyyyy(id INT PRIMARY KEY NOT NULL AUTO_INCREMENT, NAME VARCHAR(30));
CREATE TABLE zzzzz(
id INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
NAME VARCHAR(30)
);
-- 查看錶結構
-- desc 數據表的名字;
DESC xxxxx;
-- 創建students表(id、name、age、high、gender、cls_id)
CREATE TABLE students(
id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
NAME VARCHAR(30),
age TINYINT UNSIGNED DEFAULT 0,
high DECIMAL(5,2),
gender ENUM("男", "女", "中性", "保密") DEFAULT "保密",
cls_id INT UNSIGNED
);
INSERT INTO students VALUES(0, "老王", 18, 188.88, "男", 0);
SELECT * FROM students;
-- 創建classes表(id、name)
CREATE TABLE classes(
id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
NAME VARCHAR(30)
);
INSERT INTO classes VALUES(0, "python04大神");
SELECT * FROM classes;
-- 查看錶的創建語句
-- show create table 表名字;
SHOW CREATE TABLE students;
-- 修改表-添加字段
-- alter table 表名 add 列名 類型;
ALTER TABLE students ADD birthday DATETIME;
-- 修改表-修改字段:不重命名版
-- alter table 表名 modify 列名 類型及約束;
ALTER TABLE students MODIFY birthday DATE;
-- 修改表-修改字段:重命名版
-- alter table 表名 change 原名 新名 類型及約束;
ALTER TABLE students CHANGE birthday birth DATE DEFAULT "2000-01-01";
-- 修改表-刪除字段
-- alter table 表名 drop 列名;
ALTER TABLE students DROP high;
-- 刪除表
-- drop table 表名;
-- drop database 數據庫;
-- drop table 數據表;
DROP TABLE xxxxx;
-- 增刪改查(curd)
-- 增加
-- 全列插入
-- insert [into] 表名 values(...)
-- 主鍵字段 可以用 0 null default 來佔位
-- 向classes表中插入 一個班級
INSERT INTO classes VALUES(0, "菜鳥班");
+--------+-------------------------------------+------+-----+------------+----------------+
| FIELD | TYPE | NULL | KEY | DEFAULT | Extra |
+--------+-------------------------------------+------+-----+------------+----------------+
| id | INT(10) UNSIGNED | NO | PRI | NULL | AUTO_INCREMENT |
| NAME | VARCHAR(30) | YES | | NULL | |
| age | TINYINT(3) UNSIGNED | YES | | 0 | |
| gender | ENUM('男','女','中性','保密') | YES | | 保密 | |
| cls_id | INT(10) UNSIGNED | YES | | NULL | |
| birth | DATE | YES | | 2000-01-01 | |
+--------+-------------------------------------+------+-----+------------+----------------+
-- 向students表插入 一個學生信息
INSERT INTO students VALUES(0, "小李飛刀", 20, "女", 1, "1990-01-01");
INSERT INTO students VALUES(NULL, "小李飛刀", 20, "女", 1, "1990-01-01");
INSERT INTO students VALUES(DEFAULT, "小李飛刀", 20, "女", 1, "1990-01-01");
-- 失敗
-- insert into students values(default, "小李飛刀", 20, "第4性別", 1, "1990-02-01");
-- 枚舉中 的 下標從1 開始 1---“男” 2--->"女"....
INSERT INTO students VALUES(DEFAULT, "小李飛刀", 20, 1, 1, "1990-02-01");
-- 部分插入
-- insert into 表名(列1,...) values(值1,...)
INSERT INTO students (NAME, gender) VALUES ("小喬", 2);
-- 多行插入
INSERT INTO students (NAME, gender) VALUES ("大喬", 2),("貂蟬", 2);
INSERT INTO students VALUES(DEFAULT, "西施", 20, "女", 1, "1990-01-01"), (DEFAULT, "王昭君", 20, "女", 1, "1990-01-01");
-- 修改
-- update 表名 set 列1=值1,列2=值2... where 條件;
UPDATE students SET gender=1; -- 全部都改
UPDATE students SET gender=1 WHERE NAME="小李飛刀"; -- 只要name是小李飛刀的 全部的修改
UPDATE students SET gender=1 WHERE id=3; -- 只要id爲3的 進行修改
UPDATE students SET age=22, gender=1 WHERE id=3; -- 只要id爲3的 進行修改
-- 查詢基本使用
-- 查詢所有列
-- select * from 表名;
SELECT * FROM students;
---定條件查詢
SELECT * FROM students WHERE NAME="小李飛刀"; -- 查詢 name爲小李飛刀的所有信息
SELECT * FROM students WHERE id>3; -- 查詢 name爲小李飛刀的所有信息
-- 查詢指定列
-- select 列1,列2,... from 表名;
SELECT NAME,gender FROM students;
-- 可以使用as爲列或表指定別名
-- select 字段[as 別名] , 字段[as 別名] from 數據表 where ....;
SELECT NAME AS 姓名,gender AS 性別 FROM students;
-- 字段的順序
SELECT id AS 序號, gender AS 性別, NAME AS 姓名 FROM students;
-- 刪除
-- 物理刪除
-- delete from 表名 where 條件
DELETE FROM students; -- 整個數據表中的所有數據全部刪除
DELETE FROM students WHERE NAME="小李飛刀";
-- 邏輯刪除
-- 用一個字段來表示 這條信息是否已經不能再使用了
-- 給students表添加一個is_delete字段 bit 類型
ALTER TABLE students ADD is_delete BIT DEFAULT 0;
UPDATE students SET is_delete=1 WHERE id=6;
-- 消除重複行 -- distinct 字段 SELECT DISTINCT gender FROM students; -- 條件查詢 -- 比較運算符 -- select .... from 表名 where ..... -- > -- 查詢大於18歲的信息 SELECT * FROM students WHERE age>18; SELECT id,NAME,gender FROM students WHERE age>18; -- < -- 查詢小於18歲的信息 SELECT * FROM students WHERE age<18; -- >= -- <= -- 查詢小於或者等於18歲的信息 -- = -- 查詢年齡爲18歲的所有學生的名字 SELECT * FROM students WHERE age=18; -- != 或者 <> -- 邏輯運算符 -- and -- 18到28之間的所以學生信息 SELECT * FROM students WHERE age>18 AND age<28; -- 失敗select * from students where age>18 and <28; -- 18歲以上的女性 SELECT * FROM students WHERE age>18 AND gender="女"; SELECT * FROM students WHERE age>18 AND gender=2; -- or -- 18以上或者身高查過180(包含)以上 SELECT * FROM students WHERE age>18 OR height>=180; -- not -- 不在 18歲以上的女性 這個範圍內的信息 -- select * from students where not age>18 and gender=2; SELECT * FROM students WHERE NOT (age>18 AND gender=2); -- 年齡不是小於或者等於18 並且是女性 SELECT * FROM students WHERE (NOT age<=18) AND gender=2; -- 模糊查詢 -- like -- % 替換1個或者多個 -- _ 替換1個 -- 查詢姓名中 以 "小" 開始的名字 SELECT NAME FROM students WHERE NAME="小"; SELECT NAME FROM students WHERE NAME LIKE "小%"; -- 查詢姓名中 有 "小" 所有的名字 SELECT NAME FROM students WHERE NAME LIKE "%小%"; -- 查詢有2個字的名字 SELECT NAME FROM students WHERE NAME LIKE "__"; -- 查詢有3個字的名字 SELECT NAME FROM students WHERE NAME LIKE "__"; -- 查詢至少有2個字的名字 SELECT NAME FROM students WHERE NAME LIKE "__%"; -- rlike 正則 -- 查詢以 周開始的姓名 SELECT NAME FROM students WHERE NAME RLIKE "^周.*"; -- 查詢以 周開始、倫結尾的姓名 SELECT NAME FROM students WHERE NAME RLIKE "^周.*倫$"; -- 範圍查詢 -- in (1, 3, 8)表示在一個非連續的範圍內 -- 查詢 年齡爲18、34的姓名 SELECT NAME,age FROM students WHERE age=18 OR age=34; SELECT NAME,age FROM students WHERE age=18 OR age=34 OR age=12; SELECT NAME,age FROM students WHERE age IN (12, 18, 34); -- not in 不非連續的範圍之內 -- 年齡不是 18、34歲之間的信息 SELECT NAME,age FROM students WHERE age NOT IN (12, 18, 34); -- between ... and ...表示在一個連續的範圍內 -- 查詢 年齡在18到34之間的的信息 SELECT NAME, age FROM students WHERE age BETWEEN 18 AND 34; -- not between ... and ...表示不在一個連續的範圍內 -- 查詢 年齡不在在18到34之間的的信息 SELECT * FROM students WHERE age NOT BETWEEN 18 AND 34; SELECT * FROM students WHERE NOT age BETWEEN 18 AND 34; -- 失敗的select * from students where age not (between 18 and 34); -- 空判斷 -- 判空is null -- 查詢身高爲空的信息 SELECT * FROM students WHERE height IS NULL; SELECT * FROM students WHERE height IS NULL; SELECT * FROM students WHERE height IS NULL; -- 判非空is not null SELECT * FROM students WHERE height IS NOT NULL; -- 排序 -- order by 字段 -- asc從小到大排列,即升序 -- desc從大到小排序,即降序 -- 查詢年齡在18到34歲之間的男性,按照年齡從小到到排序 SELECT * FROM students WHERE (age BETWEEN 18 AND 34) AND gender=1; SELECT * FROM students WHERE (age BETWEEN 18 AND 34) AND gender=1 ORDER BY age; SELECT * FROM students WHERE (age BETWEEN 18 AND 34) AND gender=1 ORDER BY age ASC; -- 查詢年齡在18到34歲之間的女性,身高從高到矮排序 SELECT * FROM students WHERE (age BETWEEN 18 AND 34) AND gender=2 ORDER BY height DESC; -- order by 多個字段 -- 查詢年齡在18到34歲之間的女性,身高從高到矮排序, 如果身高相同的情況下按照年齡從小到大排序 SELECT * FROM students WHERE (age BETWEEN 18 AND 34) AND gender=2 ORDER BY height DESC,id DESC; -- 查詢年齡在18到34歲之間的女性,身高從高到矮排序, 如果身高相同的情況下按照年齡從小到大排序, -- 如果年齡也相同那麼按照id從大到小排序 SELECT * FROM students WHERE (age BETWEEN 18 AND 34) AND gender=2 ORDER BY height DESC,age ASC,id DESC; -- 按照年齡從小到大、身高從高到矮的排序 SELECT * FROM students ORDER BY age ASC, height DESC; -- 聚合函數 -- 總數 -- count -- 查詢男性有多少人,女性有多少人 SELECT * FROM students WHERE gender=1; SELECT COUNT(*) FROM students WHERE gender=1; SELECT COUNT(*) AS 男性人數 FROM students WHERE gender=1; SELECT COUNT(*) AS 女性人數 FROM students WHERE gender=2; -- 最大值 -- max -- 查詢最大的年齡 SELECT age FROM students; SELECT MAX(age) FROM students; -- 查詢女性的最高 身高 SELECT MAX(height) FROM students WHERE gender=2; -- 最小值 -- min -- 求和 -- sum -- 計算所有人的年齡總和 SELECT SUM(age) FROM students; -- 平均值 -- avg -- 計算平均年齡 SELECT AVG(age) FROM students; -- 計算平均年齡 sum(age)/count(*) SELECT SUM(age)/COUNT(*) FROM students; -- 四捨五入 round(123.23 , 1) 保留1位小數 -- 計算所有人的平均年齡,保留2位小數 SELECT ROUND(SUM(age)/COUNT(*), 2) FROM students; SELECT ROUND(SUM(age)/COUNT(*), 3) FROM students; -- 計算男性的平均身高 保留2位小數 SELECT ROUND(AVG(height), 2) FROM students WHERE gender=1; -- select name, round(avg(height), 2) from students where gender=1; -- 分組 -- group by -- 按照性別分組,查詢所有的性別 SELECT NAME FROM students GROUP BY gender; SELECT * FROM students GROUP BY gender; SELECT gender FROM students GROUP BY gender; -- 失敗select * from students group by gender; -- 計算每種性別中的人數 SELECT gender,COUNT(*) FROM students GROUP BY gender; -- 計算男性的人數 SELECT gender,COUNT(*) FROM students WHERE gender=1 GROUP BY gender; -- group_concat(...) -- 查詢同種性別中的姓名 SELECT gender,GROUP_CONCAT(NAME) FROM students WHERE gender=1 GROUP BY gender; SELECT gender,GROUP_CONCAT(NAME, age, id) FROM students WHERE gender=1 GROUP BY gender; SELECT gender,GROUP_CONCAT(NAME, "_", age, " ", id) FROM students WHERE gender=1 GROUP BY gender; -- having -- 查詢平均年齡超過30歲的性別,以及姓名 having avg(age) > 30 SELECT gender, GROUP_CONCAT(NAME),AVG(age) FROM students GROUP BY gender HAVING AVG(age)>30; -- 查詢每種性別中的人數多於2個的信息 SELECT gender, GROUP_CONCAT(NAME) FROM students GROUP BY gender HAVING COUNT(*)>2; -- 分頁 -- limit start, count -- 限制查詢出來的數據個數 SELECT * FROM students WHERE gender=1 LIMIT 2; -- 查詢前5個數據 SELECT * FROM students LIMIT 0, 5; -- 查詢id6-10(包含)的書序 SELECT * FROM students LIMIT 5, 5; -- 每頁顯示2個,第1個頁面 SELECT * FROM students LIMIT 0,2; -- 每頁顯示2個,第2個頁面 SELECT * FROM students LIMIT 2,2; -- 每頁顯示2個,第3個頁面 SELECT * FROM students LIMIT 4,2; -- 每頁顯示2個,第4個頁面 SELECT * FROM students LIMIT 6,2; -- -----> limit (第N頁-1)*每個的個數, 每頁的個數; -- 每頁顯示2個,顯示第6頁的信息, 按照年齡從小到大排序 -- 失敗select * from students limit 2*(6-1),2; -- 失敗select * from students limit 10,2 order by age asc; SELECT * FROM students ORDER BY age ASC LIMIT 10,2; SELECT * FROM students WHERE gender=2 ORDER BY height DESC LIMIT 0,2; -- 連接查詢 -- inner join ... on -- select ... from 表A inner join 表B; SELECT * FROM students INNER JOIN classes; -- 查詢 有能夠對應班級的學生以及班級信息 SELECT * FROM students INNER JOIN classes ON students.cls_id=classes.id; -- 按照要求顯示姓名、班級 SELECT students.*, classes.name FROM students INNER JOIN classes ON students.cls_id=classes.id; SELECT students.name, classes.name FROM students INNER JOIN classes ON students.cls_id=classes.id; -- 給數據表起名字 SELECT s.name, c.name FROM students AS s INNER JOIN classes AS c ON s.cls_id=c.id; -- 查詢 有能夠對應班級的學生以及班級信息,顯示學生的所有信息,只顯示班級名稱 SELECT s.*, c.name FROM students AS s INNER JOIN classes AS c ON s.cls_id=c.id; -- 在以上的查詢中,將班級姓名顯示在第1列 SELECT c.name, s.* FROM students AS s INNER JOIN classes AS c ON s.cls_id=c.id; -- 查詢 有能夠對應班級的學生以及班級信息, 按照班級進行排序 -- select c.xxx s.xxx from student as s inner join clssses as c on .... order by ....; SELECT c.name, s.* FROM students AS s INNER JOIN classes AS c ON s.cls_id=c.id ORDER BY c.name; -- 當時同一個班級的時候,按照學生的id進行從小到大排序 SELECT c.name, s.* FROM students AS s INNER JOIN classes AS c ON s.cls_id=c.id ORDER BY c.name,s.id; -- left join -- 查詢每位學生對應的班級信息 SELECT * FROM students AS s LEFT JOIN classes AS c ON s.cls_id=c.id; -- 查詢沒有對應班級信息的學生 -- select ... from xxx as s left join xxx as c on..... where ..... -- select ... from xxx as s left join xxx as c on..... having ..... SELECT * FROM students AS s LEFT JOIN classes AS c ON s.cls_id=c.id HAVING c.id IS NULL; SELECT * FROM students AS s LEFT JOIN classes AS c ON s.cls_id=c.id WHERE c.id IS NULL; -- right join on -- 將數據表名字互換位置,用left join完成 -- 自關聯 -- 省級聯動 url:http://demo.lanrenzhijia.com/2014/city0605/ -- 查詢所有省份 SELECT * FROM areas WHERE pid IS NULL; -- 查詢出山東省有哪些市 SELECT * FROM areas AS province INNER JOIN areas AS city ON city.pid=province.aid HAVING province.atitle="山東省"; SELECT province.atitle, city.atitle FROM areas AS province INNER JOIN areas AS city ON city.pid=province.aid HAVING province.atitle="山東省"; -- 查詢出青島市有哪些縣城 SELECT province.atitle, city.atitle FROM areas AS province INNER JOIN areas AS city ON city.pid=province.aid HAVING province.atitle="青島市"; SELECT * FROM areas WHERE pid=(SELECT aid FROM areas WHERE atitle="青島市") -- 子查詢 -- 標量子查詢 -- 查詢出高於平均身高的信息 -- 查詢最高的男生信息 SELECT * FROM students WHERE height = 188; SELECT * FROM students WHERE height = (SELECT MAX(height) FROM students); -- 列級子查詢 -- 查詢學生的班級號能夠對應的學生信息 -- select * from students where cls_id in (select id from classes);