It's Saturday again-MySQL special training,-MySQL_PHP tutorial-PHP Tutorial-php.cn

It’s Saturday again - MySQL special training, -MySQL

It’s Saturday again, another long morning~ Let’s start after lunch

1. MySQL

-----Subquery and Connection (3)-----

----Use INSERT...SELECT to insert records

--English version of database content

Because the MYSQL console in my WAMP showed that the Chinese language was weak, and I was exhausted during the change process, I changed my tactics and changed the data to all English. I am sharing it now

--Create data table

CREATE TABLE IF NOT EXISTS goods(
goods_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
goods_name VARCHAR(150) NOT NULL,
goods_cate VARCHAR(40) NOT NULL,
brand_name VARCHAR(40) NOT NULL,
goods_price DECIMAL(15,3) UNSIGNED NOT NULL DEFAULT 0,
is_show BOOLEAN NOT NULL DEFAULT 1,
is_saleoff BOOLEAN NOT NULL DEFAULT 0
);

-- Write record

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('R510VC 15.6Inches Laptop','Laptop','ASUS','3399',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Y400N 14.0Inches Laptop','Laptop','Lenovo','4899',DEFAULT,DEFAULT);

INSERT goods ( goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('G150TH 15.6Inches Gamebook','Gamebook','ThunderGod','8499',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate ,brand_name,goods_price,is_show,is_saleoff) VALUES('X550CC 15.6Inches Laptop','Laptop','ASUS','2799',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name, goods_price,is_show,is_saleoff) VALUES('X240(20ALA0EYCD) 12.5InchesUltrabook','Ultrabook','Lenovo','4999',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price ,is_show,is_saleoff) VALUES('U330P 13.3Inches Ultrabook','Ultrabook','Lenovo','4299',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show, is_saleoff) VALUES('SVP13226SCB 13.3Inches Touch Ultrabook','Ultrabook','Sony','7999',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iPad mini MD531CH/A 7.9Inches Tablet','Tablet','Apple','1998',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff ) VALUES('iPad Air MD788CH/A 9.7Inches Tablet (16G WiFi Vision)','Tablet','Apple','3388',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name ,goods_price,is_show,is_saleoff) VALUES(' iPad mini ME279CH/A with Retina screen 7.9InchesTablet (16G WiFi Vision)','Tablet','Apple','2788',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('IdeaCentre C340 20Inches All-in-one ','Desktop','Lenovo','3499',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Vostro 3800-R1206 desktop','Desktop','Dell','2899',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iMac ME086CH/A 21.5Inches All-in-one','Desktop','Apple','9188',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('AT7-7414LP Desktop (i5-3450 4G 500G 2GIndependent graphics card DVD Keyboard&Mouse Linux )','Desktop','Acer','3699 ',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Z220SFF F4F06PAWork station','server/Work station','HP','4288' ,DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('PowerEdge T110 IIserver','server/Work station','Dell','5388', DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Mac Pro MD878CH/A Professional Desktop','server/Work station','Apple',' 28888',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' HMZ-T3W Headset Display Device','Laptop accessory','Sony',' 6999',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Business Backpage','Laptopaccessory','Sony','99',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('X3250 M4 server 2583i14','server/Work station','IBM','6888',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Xuanlong Laptop Radiator','Laptop accessory','Windgod','',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' HMZ-T3W Headset Display Device','Laptop accessory','Sony','6999',DEFAULT,DEFAULT);

INSERT goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Business Backpage','Laptop accessory','Sony','99',DEFAULT,DEFAULT);

---INSERT...SELECT

INSERT [INTO] tbl_name [(col_name)] SELECT

Just like this when using it, create a new table

CREATE TABLE IF NOT EXISTS cates(

cate_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,

cate_name VARCHAR(40) NOT NULL

);

Then selectively insert the things in the original data table

INSERT INTO CATES(CATE_NAME) SELECT GOODS_CATE FROM GOODS GROUP BY GOODS_CATE;

If we need to update our parameter table based on the catalog table categories - multi-table update

----Multiple table update

--Multiple steps

UPDATE table_ref SET col_name=... ...

Among them, ref is the reference relationship of the table

There are connections here, INNER JOIN LEFT JOIN, etc.

The simplest one is INNER, inner connection

mysql> UPDATE GOODS INNER JOIN CATES ON GOODS_CATE=CATE_NAME
-> SET GOODS_CATE=CATE_ID;

(Please forgive me for not typing in lowercase...)

Explain: update the goods table, internally connect the categories table, under what conditions - goods_cate=cate_name, what is the set value, it is the cate_id in the categories table

mysql> SELECT * FROM GOODSG; Verify it

--One step

CREATE...SELECT...

That is, creating the table and writing the connected data at the same time

The example here is: making a connection update to the brand

mysql> SELECT BRAND_NAME FROM GOODS GROUP BY BRAND_NAME;

mysql> CREATE TABLE IF NOT EXISTS brands(
-> brand_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
-> brand_name VARCHAR(40) NOT NULL
-> )
-> ; SELECT BRAND_NAME FROM GOODS GROUP BY BRAND_NAME;

You can save the INSERT operation

But the update will go wrong at this time

mysql> UPDATE GOODS INNER JOIN BRANDS ON BRAND_NAME=BRAND_NAME
-> SET BRAND_NAME=BRAND_ID;
ERROR 1052 (23000): Champ: 'BRAND_NAME' dans field list est ambigu

Because the names are the same, we need to change the field or use an alias AS

mysql> UPDATE GOODS AS G INNER JOIN BRANDS AS B ON G.BRAND_NAME=B.BRAND_NAME
-> SET G.BRAND_NAME=BRAND_ID;

Although the appearance has been updated, for example, the type of goods_cate is still varchar, and we actually want it to be of type int in the main table. At this time, because you need to modify the field name and data type, use ALTER CHANGE

mysql> ALTER TABLE GOODS
-> CHANGE GOODS_CATE CATE_ID SMALLINT UNSIGNED NOT NULL,
-> CHANGE BRAND_NAME BRAND_ID SMALLINT UNSIGNED NOT NULL;

This kind of foreign key is called a fact foreign key, and it has more physical foreign keys than the foreign key

----Connect

Since we have implemented multi-table storage, but due to display and other requirements, multiple tables are required to be linked, and a connection is required

Data table reference ref: tbl_name [[AS] alias] | table_subquery [AS] alias

---INNER JOIN

Use ON to set connection conditions, WHERE generally performs further filtering

Inner connection, only display records that meet the connection conditions

SELECT GOODS_ID,GOODS_NAME,CATE_NAME FROM GOODS INNER JOIN CATES ON GOODS.CATE_ID=CATES.CATE_ID;

Translation: Select the goods_id, goods_name, cate_name fields in the goods table, but when displaying, you need to connect the cates table internally (because we don’t want to display the numerical representation of the type), the condition is that the cate_id fields of the two are equal ;Here, since cate_id is not given an alias, it is written as table name.cate_id

You will find that the display of this inner connection only displays the results of the on condition

---Outer join

Outer joins are divided into left outer and right outer joins

LEFT JOIN displays all the records in the left table and the records in the right table that meet the link conditions. The example is as follows

注意最后一个记录的类名是null

RIGHT JOIN是这样的

----多表连接

mysql> SELECT GOODS_ID,GOODS_NAME,CATE_NAME,BRAND_NAME,GOODS_PRICE FROM GOODS AS G
-> INNER JOIN CATES AS C ON G.CATE_ID=C.CATE_ID
-> INNER JOIN BRANDS AS B ON G.BRAND_ID=B.BRAND_ID;

每连接一个表就需要一个JOIN，注意起别名给数据表！

此时的显示虽然跟一开始一样，但实现不同，意义大不一样

----无限级分类表设计

一般实际中会出现无限级数据表，不断往下分

举个例子

CREATE TABLE goods_types(
type_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
type_name VARCHAR(20) NOT NULL,
parent_id SMALLINT UNSIGNED NOT NULL DEFAULT 0
);

INSERT goods_types(type_name,parent_id) VALUES('Home Electronics',DEFAULT);
INSERT goods_types(type_name,parent_id) VALUES('PC、Office',DEFAULT);
INSERT goods_types(type_name,parent_id) VALUES('Appliances',1);
INSERT goods_types(type_name,parent_id) VALUES('Life Appliances',1);
INSERT goods_types(type_name,parent_id) VALUES('Tablet TV',3);
INSERT goods_types(type_name,parent_id) VALUES('Air Conditioner',3);
INSERT goods_types(type_name,parent_id) VALUES('Electrical Fan',4);
INSERT goods_types(type_name,parent_id) VALUES('Water Dispenser',4);
INSERT goods_types(type_name,parent_id) VALUES('Complete Machine',2);
INSERT goods_types(type_name,parent_id) VALUES('Accessory',2);
INSERT goods_types(type_name,parent_id) VALUES('Laptop',9);
INSERT goods_types(type_name,parent_id) VALUES('Ultrabook',9);
INSERT goods_types(type_name,parent_id) VALUES('Gamebook',9);
INSERT goods_types(type_name,parent_id) VALUES('CPU',10);
INSERT goods_types(type_name,parent_id) VALUES('Host Computer',10);

mysql> SELECT * FROM GOODS_TYPES;
--------- ------------------ -----------
| type_id | type_name | parent_id |
--------- ------------------ -----------
| 1 | Home Electronics | 0 |
| 2 | PC?Office | 0 |
| 3 | Appliances | 1 |
| 4 | Life Appliances | 1 |
| 5 | Tablet TV | 3 |
| 6 | Air Conditioner | 3 |
| 7 | Electrical Fan | 4 |
| 8 | Water Dispenser | 4 |
| 9 | Complete Machine | 2 |
| 10 | Accessory | 2 |
| 11 | Laptop | 9 |
| 12 | Ultrabook | 9 |
| 13 | Gamebook | 9 |
| 14 | CPU | 10 |
| 15 | Host Computer | 10 |
--------- ------------------ -----------

注意parent_id，是指改节点的级别，比如0，表示home electronics没有父节点，是个顶级节点

查找的实现，是通过自身连接来完成的

---自身连接

举个例子，显示所有类别的父类是什么

这里，自身的连接，可以想象右边有一张一模一样的表（左边也可以，有些东西稍微变一下就行）

翻译一下，就是，可以先从条件说起，当子表s中的parent_id=父表中的type_id时，选取子表的type_id,type_name,以及父表的type_name显示，这里的别名可以在语句的末尾处显示

要把这个逻辑关系先说说/想想清楚，再翻译为sql语句

反过来，查找所有类别的子类

先考虑逻辑关系：当父表的type_id=子表的parent_id时，取 P.TYPE_ID,P.TYPE_NAME,S.TYPE_NAME ——再写出语句

再复杂一点，且留给你们自己翻译

mysql> SELECT P.TYPE_ID,P.TYPE_NAME,COUNT(S.TYPE_NAME) CHILD_COUNT FROM GOODS_TYPES AS P LEFT JOIN GOODS_TYPES AS S
-> ON P.TYPE_ID=S.PARENT_ID GROUP BY P.TYPE_NAME ORDER BY P.TYPE_ID;
--------- ------------------ -------------
| TYPE_ID | TYPE_NAME | CHILD_COUNT |
--------- ------------------ -------------
| 1 | Home Electronics | 2 |
| 2 | PC?Office | 2 |
| 3 | Appliances | 2 |
| 4 | Life Appliances | 2 |
| 5 | Tablet TV | 0 |
| 6 | Air Conditioner | 0 |
| 7 | Electrical Fan | 0 |
| 8 | Water Dispenser | 0 |
| 9 | Complete Machine | 3 |
| 10 | Accessory | 2 |
| 11 | Laptop | 0 |
| 12 | Ultrabook | 0 |
| 13 | Gamebook | 0 |
| 14 | CPU | 0 |
| 15 | Host Computer | 0 |
--------- ------------------ -------------

----多表删除

基本思路也是通过一张表模拟多张表的操作

懒了，直接复制看吧，需要了再去做

-- INSERT ... SELECT实现复制

INSERT goods(goods_name,cate_id,brand_id) SELECT goods_name,cate_id,brand_id FROM goods WHERE goods_id IN (19,20);

-- 查找重复记录

SELECT goods_id,goods_name FROM goods GROUP BY goods_name HAVING count(goods_name) >= 2;

-- 删除重复记录

DELETE t1 FROM goods AS t1 LEFT JOIN (SELECT goods_id,goods_name FROM goods GROUP BY goods_name HAVING count(goods_name) >= 2 ) AS t2 ON t1.goods_name = t2.goods_name WHERE t1.goods_id > t2.goods_id;