SQL难点求解,聚合不应出现在

修改语句:

子查询与连接
数量筹算

SQL难点求解!SQL难点求解!
美高梅开户网址 1

–SELECT * FROM sale_detail sd WHERE split_count IS NOT NULL

update A set WZCount=ISNULL(WZCount,0)+(select SUM(WZCount) from
T_PM_OutStock_SUB where MaterialID =A.MaterialID and
_MainID='{_AutoID}’) from T_PM_MaterialStock A,T_PM_OutStock_SUB

一、复习:
MYSQL记录操作:写操作(insert、update、delete)和读操作select
二 子查询和一而再
tdb_goods表结构
good_id—商品ID good_name—商品名称 good_eate 商品品种
brand_name 品牌名称 goods_price 商品价位 is_show 是还是不是上架
is_saleoff 是还是不是售空
固然如此MySQL配置了客户端和服务器的编码格式均为utf八编码,但在已建的数量表插入记录时,MySQL如故不识别中文,会抛出Incorrect
String Value万分。
该难点的消除办法即:

SELECT a.PNO ,
a.Uname ,
isnull(a.pronum – b.SPCnumber,0) AS sjxsnum
FROM ( SELECT TOP 100 PERCENT
cong.PNO ,
zhu.Uname ,
SUM(cong.BenCiNum) pronum
FROM dbo.TBFaHuo zhu
RIGHT JOIN ( SELECT PNO ,
BenCiNum ,
FhId
FROM dbo.TBFaHuoDetail c
) cong ON zhu.FhId = cong.fhId
WHERE cong.PNO = ‘kl008’
GROUP BY zhu.Uname ,
cong.PNO
ORDER BY ProNum DESC
) a
LEFT JOIN
( SELECT TOP 100 PERCENT
ddmx.PNO ,
dd.UName ,
SUM(thmx.SPCnumber) SPCnumber
FROM dbo.TBSalesReturnPro thmx
INNER JOIN ( SELECT id ,
pno ,
oid
FROM dbo.TBOrderPro mx
) ddmx ON ddmx.ID = thmx.OPID
INNER JOIN ( SELECT OID ,
UName
FROM TBOrder
) dd ON dd.OID = ddmx.oid
WHERE ddmx.PNO = ‘kl008’
GROUP BY ddmx.PNO ,
dd.UName
) b ON b.UName = a.Uname

–SELECT * FROM sale_detail sd WHERE split_amount IS NULL

系统报错:

  1. 在插入记录从前,通过SET NAMES
    gbk;设置客户端的编码格式,即敲入的是哪些编码,客户端会自动将插入命令转变到utf八编码
  2. 自然在查询记录在此之前,也急需通过SET NAMES
    gbk;设置客户端数据呈现的编码,不然会冒出乱码
  3. SET NAMES gbk;只会影响客户端展示数据的编码,对源数据不会有别的影响
    子查询
    1.子查询是提出现在【别的SQL语句内】的SELECT子句
    eg:
    SELECT * FROM t1 WHERE column1 = (SELECT column1 FROM t2);
    其中,SELECT * FROM t1 …称为Outer Query[外查询](或者Outer
    Statement)
    SELECT column1 FROM t2 称为Sub Query[子查询]
    ps:Outer
    Query[外查询]并不止指SELECT等查询语句,而是兼具的SQL语句,当叁个SQL语句包括了子查询,则包括子查询的言辞就叫外查询
    二子查询的原则:
    一)始终出现在圆括号内;
    二)可以包括四个至关主要字恐怕条件;如 distinct、group by、order
    by、limit、函数等 (改为题写)
    三)子查询的外查询可以是:【SELECT,INSERT,UPDATE,SET或DO】。SQL语句的统称
    三.子查询的再次来到值
    子查询能够回去标量、一行、1列或子查询

沾满错误的sql语句,希望指正!

SET NOCOUNT OFF

汇集不应出现在 UPDATE 语句的集纳列表中

动用相比运算符的子查询
选取相比较运算符
=、>、<、>=、<=、<>、!=、<=>
语法结构
operand comparison_operator subquery

WHILE 1=1

问题:

SELECT AVG (col_name) FROM tbl_name;
寻觅数据表中某列的平均值

BEGIN

修改语句中不可能冒出聚合函数那一类的

SELECT AVG(goods_price) FROM tdb_goods; //AVG函数代表求其平均值//
SELECT ROUND(AVG(goods_price),2) FROM tdb_goods;
//round(@,#)代表对@数字举办肆舍5入,且保留小数点后#位输出//
SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE
goods_price>=53玖壹.30; //输出价格超过5391.30的id、name、price//
回顾起来运用子查询时:
SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE
goods_price>=(SELECT ROUND(AVG(goods_price),2) FROM tdb_goods);
//查找价格高于平均值的货色//
SELECT goods_price FROM tdb_price WHERE goods_cate=’超级本’\G;
//检索分类为”超极本”的货品价位且一网格呈现//
对此ANY、SOME、ALL的用法各有差异:(ANY和SOME用法同样)
SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE
goods_price>=ANY (SELECT goods_price FROM tdb_goods WHERE
goods_cate=’超级本’);

WITH cte AS

化解难题:

SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE
goods_price>=ALL (SELECT goods_price FROM tdb_goods WHERE
goods_cate=’超级本’);

(

这就把聚合函数放到select 查询与查出来当成1个数额表 
 再用数据表和原来的多少表相配 进行增加

SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE
goods_price>=SOME (SELECT goods_price FROM tdb_goods WHERE
goods_cate=’超级本’);
第两种子查询—[NOT] IN
in 相当于 = any
not in 相当于 != all 或者<>all ——不等于、不包含
子查询—-exists not exists ——用得比较少
子查询重回任何行 exists 返回 true 反之 重回 false
— = ANY 或 = SOME 等价于 IN
EG:SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE
goods_price !=ALL (SELECT goods_price FROM tdb_goods WHERE
goods_cate=’超级本’ )//得到19个记录(22-3)
SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE
goods_price IN (SELECT goods_price FROM tdb_goods WHERE goods_cate =
‘超级本’)
//得到3个记录
其三种子查询.使用 [NOT] EXISTS 的子查询(较少用)
子查询的下结论
一.子查询是指在另1个查询语句中的SELECT子句。
例句:
SELECT * FROM t1 WHERE column1 = (SELECT column1 FROM t2);
其中,SELECT * FROM t1 …称为Outer Query[外查询](或者Outer
Statement),
SELECT column1 FROM t2 称为Sub Query[子查询]。
为此,大家说子查询是嵌套在外查询内部。而事实上它有望在子查询内部再嵌套子查询。
子查询必须出现在圆括号之间。
行级子查询
SELECT * FROM t1 WHERE (col1,col2) = (SELECT col3, col4 FROM t2 WHERE
id = 10);
SELECT * FROM t1 WHERE ROW(col1,col2) = (SELECT col3, col4 FROM t2
WHERE id = 10);
行级子查询的归来结果最多为一行。
优化子查询
— 创立数据表
CREATE TABLE IF NOT EXISTS tdb_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
);

SELECT TOP (100000) * FROM dbo.sale_detail WHERE split_count IS NULL
OR split_amount IS NULL

修改之后;

— 写入记录

 

UPDATE T_PM_MaterialStock
SET WZCount = WZCount+TB.ALLCount
FROM (SELECT
b.MaterialID,SUM(b.Count) AS ALLCount
FROM
T_PM_MaterialStock a
INNER JOIN
T_PM_SQL难点求解,聚合不应出现在。OutStock_SUB b
ON a.MaterialID = b.MaterialID
WHERE b._MainID='{_AutoID}’
GROUP BY
b.MaterialID
) AS TB
WHERE
T_PM_MaterialStock.MaterialID = TB.MaterialID

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘中华V510VC
壹伍.陆英寸台式机’,’台式机’,’ASUS’,’339九’,DEFAULT,DEFAULT);

)

健康示例:

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘Y400N
1四.0英寸台式机Computer’,’台式机’,’联想’,’489九’,DEFAULT,DEFAULT);

UPDATE ssd SET
ssd.split_count=tt.split_count,ssd.split_amount=tt.split_amount

UPDATE    库存表2
SET              库存数量 = TB.剩余数量
FROM  (SELECT 
      入库表.条形码,SUM(入库表.剩余数量) AS 剩余数量
      FROM  
      库存表2 
      INNER JOIN
      入库表 
      ON 库存表2.条形码 = 入库表.条形码 
      GROUP BY
      入库表.条形码
      ) AS TB 
      WHERE
      库存表2.条形码 = TB.条形码
另外一个语句写的例子:

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘G150TH
一伍.6英寸上网本’,’笔记本’,’雷公’,’8499′,DEFAULT,DEFAULT);

FROM cte ssd

UPDATE T_PM_MaterialEntry_SUB
SET Surplus = ISNULL(Surplus,0)+TB.ALLCount
FROM (SELECT
b.SourceNumID,SUM(b.Count) AS ALLCount
FROM
T_PM_MaterialEntry_SUB a
INNER JOIN
T_PM_OutStock_SUB b
ON a._AutoID = b.SourceNumID
WHERE b._MainID='{_AutoID}’
GROUP BY
b.SourceNumID
) AS TB
WHERE
T_PM_MaterialEntry_SUB._AutoID = TB.SourceNumID

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘X550CC
15.陆英寸台式机’,’台式机’,’Alienware’,’2799′,DEFAULT,DEFAULT);

JOIN (

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘X240(20ALA0EYCD)
12.伍英寸超极本’,’一级本’,’联想’,’499九’,DEFAULT,DEFAULT);

SELECT a.rid,SUM(ISNULL(a.split_units,0)) AS
split_count,SUM(ISNULL(a.split_rmb,0)) AS split_amount

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘U330P 13.3英寸超极本’,’一级本’,’联想’,’429九’,DEFAULT,DEFAULT);

FROM (

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘SVP13226SCB
一叁.三英寸触控超极本’,’一流本’,’Sony’,’7999′,DEFAULT,DEFAULT);

SELECT sd.rid, SUM(( CASE WHEN pk.count IS NULL THEN 1 ELSE pk.count END
) * sd.count) AS split_units,

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘三星平板 mini MD53一CH/A
7.玖英寸iPad’,’华为平板’,’苹果’,’一九九玖’,DEFAULT,DEFAULT);

SUM(CASE WHEN pk.price IS NULL THEN sd.amount ELSE pk.price * pk.count
* sd.count END ) AS split_rmb

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘三星GALAXY Tab Air MD78八CH/A 九.柒英寸三星平板 (16G
WiFi版)’,’GALAXY Tab’,’苹果’,’3388′,DEFAULT,DEFAULT);

FROM cte sd WITH(NOLOCK)

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘ 华为平板 mini ME27玖CH/A 配备 Retina 显示屏 7.九英寸GALAXY Tab (16G
WiFi版)’,’华为平板’,’苹果’,’278八’,DEFAULT,DEFAULT);

LEFT JOIN product p WITH(NOLOCK) ON p.product_id = sd.product_id

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘IdeaCentre C340 20英寸一体Computer’,’台式机’,’联想’,’349九’,DEFAULT,DEFAULT);

LEFT JOIN product_kit pk WITH(NOLOCK) ON pk.kit_id = p.product_id

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘Vostro 3800-Odyssey1206台式Computer’,’台式机’,’戴尔’,’289玖’,DEFAULT,DEFAULT);

AND pk.status = 0

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘iMac ME0八六CH/A
二一.5英寸一体Computer’,’台式机’,’苹果’,’918八’,DEFAULT,DEFAULT);

AND sd.sale_date >= pk.start_date

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘AT7-741四LP 台式计算机 (i伍-3450四核 四G 500G 二G独显 mp5 键鼠 Linux
)’,’台式机’,’ASUS’,’369玖’,DEFAULT,DEFAULT);

AND sd.sale_date <= pk.end_date

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘Z220SFF
F4F06PA工作站’,’服务器/工作站’,’惠普’,’4288′,DEFAULT,DEFAULT);

WHERE sd.status = 0

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘PowerEdge T110
II服务器’,’服务器/工作站’,’戴尔’,’5388′,DEFAULT,DEFAULT);

AND p.status <> 1

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘Mac Pro MD878CH/A
专门的学业级台式计算机’,’服务器/事业站’,’苹果’,’2888八’,DEFAULT,DEFAULT);

AND p.ispromotion = 0

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘ HMZ-T3W
头戴呈现设备’,’台式机配件’,’索尼(Sony)’,’699玖’,DEFAULT,DEFAULT);

GROUP BY sd.rid

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘商务双肩信封包’,’台式机配件’,’Sony’,’9九’,DEFAULT,DEFAULT);

) a

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘X3250 M四机架式服务器
25捌3i1肆’,’服务器/职业站’,’IBM’,’688八’,DEFAULT,DEFAULT);

GROUP BY a.rid

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘玄龙尊品型台式机散热器’,’台式机配件’,’九州风姑姑’,”,DEFAULT,DEFAULT);

) tt ON ssd.rid = tt.rid

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘ HMZ-T3W
头戴展现设备’,’台式机配件’,’索尼(Sony)’,’699玖’,DEFAULT,DEFAULT);

 IF @@ROWCOUNT<100000 BREAK;

INSERT tdb_goods
(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)
VALUES(‘商务双肩信封包’,’台式机配件’,’索尼(Sony)’,’9九’,DEFAULT,DEFAULT);

end


求全数计算机产品的平均价格,并且保留两位小数,AVG,MAX,MIN、COUNT、SUM为聚合函数
SELECT ROUND(AVG(goods_price),2) AS avg_price FROM tdb_goods;
— 查询全数价格高于平均价格的货物,并且按价格降序排序
SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE
goods_price > 5845.10 ORDER BY goods_price DESC;
— 使用子查询来兑现
SELECT goods_id,goods_name,goods_price FROM tdb_goods
WHERE goods_price > (SELECT ROUND(AVG(goods_price),2) AS avg_price
FROM tdb_goods)
ORDER BY goods_price DESC;
— 查询类型为“超记本”的物品价位
SELECT goods_price FROM tdb_goods WHERE goods_cate = ‘超级本’;
— 查询价格超越或等于”超级本”价格的物品,并且按价格降序排列
SELECT goods_id,goods_name,goods_price FROM tdb_goods
WHERE goods_price = ANY(SELECT goods_price FROM tdb_goods WHERE
goods_cate = ‘超级本’)
ORDER BY goods_price DESC;
— = ANY 或 = SOME 等价于 IN
SELECT goods_id,goods_name,goods_price FROM tdb_goods
WHERE goods_price IN (SELECT goods_price FROM tdb_goods WHERE
goods_cate = ‘超级本’)
ORDER BY goods_price DESC;
— 创造“商品分类”表
CREATE TABLE IF NOT EXISTS tdb_goods_cates(
cate_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
cate_name VARCHAR(40)
);
— 查询tdb_goods表的具备记录,并且按”体系”分组
SELECT goods_cate FROM tdb_goods GROUP BY goods_cate;
— 将分组结果写入到tdb_goods_cates数据表
INSERT tdb_goods_cates (cate_name) SELECT goods_cate FROM tdb_goods
GROUP BY goods_cate;
— 通过tdb_goods_cates数据表来更新tdb_goods表
UPDATE tdb_goods INNER JOIN tdb_goods_cates ON goods_cate =
cate_name
SET goods_cate = cate_id ;
— 通过CREATE…SELECT来创建数据表并且还要写入记录
— SELECT brand_name FROM tdb_goods GROUP BY brand_name;
CREATE TABLE tdb_goods_brands (
brand_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
brand_name VARCHAR(40) NOT NULL
) SELECT brand_name FROM tdb_goods GROUP BY brand_name;
— 通过tdb_goods_brands数据表来更新tdb_goods数据表(错误)
UPDATE tdb_goods INNER JOIN tdb_goods_brands ON brand_name =
brand_name
SET brand_name = brand_id;
— Column ‘brand_name’ in field list is ambigous
— 正确
UPDATE tdb_goods AS g INNER JOIN tdb_goods_brands AS b ON
g.brand_name = b.brand_name
SET g.brand_name = b.brand_id;
— 查看tdb_goods的数据表结构
DESC tdb_goods;
— 通过ALTE普拉多 TABLE语句修改数据表结构
ALTER TABLE tdb_goods
CHANGE goods_cate cate_id SMALLINT UNSIGNED NOT NULL,
CHANGE brand_name brand_id SMALLINT UNSIGNED NOT NULL;
— 分别在tdb_goods_cates和tdb_goods_brands表插入记录
INSERT tdb_goods_cates(cate_name)
VALUES(‘路由器’),(‘交换机’),(‘网卡’);
INSERT tdb_goods_brands(brand_name)
VALUES(‘海尔(Haier)’),(‘哈工业余大学学同方’),(‘神舟’);
— 在tdb_goods数据表写入随意记录
INSERT tdb_goods(goods_name,cate_id,brand_id,goods_price) VALUES(‘
LaserJet Pro P160陆dn 黑白激光打字与印刷机’,’1二’,’肆’,’1849′);
— 查询全数商品的详细音讯(通过内三番五次完结)
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM
tdb_goods AS g
INNER JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
INNER JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;
— 查询全部商品的详细音信(通过左外连接达成)
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM
tdb_goods AS g
LEFT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
LEFT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;
— 查询全数商品的详细新闻(通过右外连接落成)
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM
tdb_goods AS g
RIGHT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
RIGHT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;
— Infiniti分类的数据表设计
CREATE TABLE tdb_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 tdb_goods_types(type_name,parent_id)
VALUES(‘家电’,DEFAULT);
INSERT tdb_goods_types(type_name,parent_id)
VALUES(‘电脑、办公’,DEFAULT);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘大家电’,1);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘生活电器’,1);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘平板电视机’,三);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘空调’,3);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘电风扇’,4);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘饮水机’,4);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘计算机完全’,贰);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘Computer配件’,二);
INSERT tdb_美高梅开户网址 ,goods_types(type_name,parent_id) VALUES(‘笔记本’,9);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘超级本’,9);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘游戏本’,9);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘CPU’,10);
INSERT tdb_goods_types(type_name,parent_id) VALUES(‘主机’,10);
— 查找全体分类及其父类
SELECT s.type_id,s.type_name,p.type_name FROM tdb_goods_types AS s
LEFT JOIN tdb_goods_types AS p ON s.parent_id = p.type_id;
— 查找全数分类及其子类
SELECT p.type_id,p.type_name,s.type_name FROM tdb_goods_types AS p
LEFT JOIN tdb_goods_types AS s ON s.parent_id = p.type_id;
— 查找全数分类及其子类的多寡
SELECT p.type_id,p.type_name,count(s.type_name) AS children_count
FROM tdb_goods_types AS p LEFT JOIN tdb_goods_types AS s ON
s.parent_id = p.type_id GROUP BY p.type_name ORDER BY p.type_id;
— 为tdb_goods_types添加child_count字段
ALTER TABLE tdb_goods_types ADD child_count MEDIUMINT UNSIGNED NOT
NULL DEFAULT 0;
— 将刚刚查询到的子类数量更新到tdb_goods_types数据表
UPDATE tdb_goods_types AS t1 INNER JOIN ( SELECT
p.type_id,p.type_name,count(s.type_name) AS children_count FROM
tdb_goods_types AS p
LEFT JOIN tdb_goods_types AS s ON s.parent_id = p.type_id
GROUP BY p.type_name
ORDER BY p.type_id ) AS t2
ON t1.type_id = t2.type_id
SET t1.child_count = t2.children_count;
— 复制编号为1二,20的两条记下
SELECT * FROM tdb_goods WHERE goods_id IN (19,20);
— INSERT … SELECT落实复制
INSERT tdb_goods(goods_name,cate_id,brand_id) SELECT
goods_name,cate_id,brand_id FROM tdb_goods WHERE goods_id IN
(19,20);
— 查找重复记录
SELECT goods_id,goods_name FROM tdb_goods GROUP BY goods_name HAVING
count(goods_name) >= 2;
— 删除重复记录
DELETE t1 FROM tdb_goods AS t1 LEFT JOIN (SELECT goods_id,goods_name
FROM tdb_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;
INSERT SELECT 插入数据
INSERT [INTO] tbl_name SET
col_name={exprDEFAULT},…//能够使用子查询
INSERT [INTO] tbl_name [(col_name,…)] SELECT
…//将查询结果写入数据表
Eg:
INSERT INTO table_name [(column_name)] SELECT column_name2 FROM
table_name2 GROUP BY column_name3;
CREATE TABLE IF NOT EXISTS tdb_goods_cates(
cate_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
cate_name VARCHAR(40) NOT NULL
);
SELECT goods_cate FROM tdb_goods GROUP BY goods_cate;
//列出富有品牌cate
DESC tdb_goods_cates; //显示出tdb_goods_cates表中的项目名称,与SHOW
COLUMNS FROM tdb_goods_cates;功用同样
INSERT tdb_goods_cates(cate_name) SELECT goods_cate FROM tdb_goods
GROUP BY goods_cate;//在表tdb_goods_cates中插入tdb_goods中的cate
多表更新:
UPDATE table_references SET col_name1={expr1 | DEFAULT}
[,col_name2={expr2 | DEFAULT}]… [WHERE where_condition]
INNER JOIN,内连接
在MySQL中,JOIN, CROSS JOIN 和 INNE奥迪Q7 JOIN 是等价的。
LEFT [OUTER] JOIN ,左外连接
RIGHT [OUTER] JOIN,右外连接
update tdb_goods inner join tdb_goods_cates on goods_cate=cate_name
set goods_cate=cate_id;

tdb_goods:想要改造的表名
inner join: 内连接
tdb_goods_cates: 关联的附表
goods_cate=cate_name 多个表对应列的涉嫌
goods_cate=cate_id; 设置 值

多表更新之一步到位
建表、查询、写入三合壹:
CREATE TABLE tdb_goods_brands (
brand_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
brand_name VARCHAR(40) NOT NULL
) SELECT brand_name FROM tdb_goods GROUP BY brand_name;
多表更新:
UPDATE tdb_goods AS g INNER JOIN tdb_goods_brands AS b ON
g.brand_name = b.brand_name SET g.brand_name = b.brand_id;
透过ALTE昂科拉 TABLE语句修改数据表结构
ALTER TABLE tdb_goods
CHANGE goods_cate cate_id SMALLINT UNSIGNED NOT NULL,
CHANGE brand_name brand_id SMALLINT UNSIGNED NOT NULL;
PS:
外键,不自然是物理的外键,逻辑的外键也行,当然,物理外键更能有限匡助数据的完整性和一致性。
数字类型的字段占用的半空中更加小,查询的频率也越来越高。
连年的语法结构
1.连接
MySQL在SELECT语句、多表更新、多表删除语句中匡助JOIN操作。
语法结构
table reference A
{[INNER|CROSS] JOIN | {LEFT|RIGHT} [OUTER] JOIN}
table_reference B
ON condition_expr
二.数据表参照
table_reference
tbl_name [[AS] alias] | table_subquery [AS] alias
数据表能够使用tbl_name AS alias_name 或 tbl_name
alias_name赋予别名。
table_subquery能够看作子查询使用在FROM子句中,那样的子查询必须为其给予别称。
内连接
1.内连接:
在MySQL中JOIN,INNE福睿斯 JOIN,CROSS JOIN是等价的
掺杂 仅显示A、B两表符合连接条件的笔录。不切合连接条件的记录不显得。
例如:SELECT goods_id,goods_name,cate_name FROM tdb_goods INNER JOIN
tdb_goods_cate ON tdb_goods.cate_id = tdb_goods_cate.cate_id;
2.外连接:
LEFT JOIN左外连接;奥迪Q7IGHT JOIN右外接连
左外连接:LEFT OUTELX570JOIN:显示左表的全体记录及右表符合连接条件的记录。
右外连接:LX570IGHT OUTEPRADOJOIN:展现右表的整整笔录及左表符合连接条件的记录。
借使使用LEFT
JOIN,左表中存在一条记录A,在右表中从不找到相应的笔录,则在重回结果用会冒出一条只有记录A中的相应字段内容,其余字段都为NULL在笔录(GL450IGHT
JOIN类似).
内接连比外链接用的多一些
三.接连条件:
运用ON设定连接条件,也足以用WHERE取代
诚如意况下接纳 ON:设定连接条件 WHERE:进行结果集记录的过滤
OUTER JOIN
1、LEFT JOIN:展现左表全体和左右顺应连接条件的记录
二、陆风X八IGHT JOIN:展现左右契合连接条件的笔录和右表全体记录
三、假如应用LEFT
JOIN,左表中留存一条记录A,在右表中从来不找到呼应的笔录,则在回来结果用会油然则生一条只有记录A中的相应字段内容,其余字段都为NULL在笔录(奇骏IGHT
JOIN类似).
— 查询全体商品的详细消息(通过左外连接落成)
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM
tdb_goods AS g
LEFT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
LEFT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;
— 查询全部商品的详细消息(通过右外连接达成)
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM
tdb_goods AS g
RIGHT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
RIGHT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;
查询语句+内连接:呈现符合五个表的1道特性的笔录;
询问语句+左连接:显示符合左表内的全体内容的记录
查询语句+右连接:彰显符合右表内的全体内容的笔录
多表连接
多表的总是跟两张表的接连一样
表的接二连三实质正是外键的逆向约束
*/
Eg:
SELECT goods_id,goods_name,b.cate_name,c.brand_name,goods_price
FROM products AS a INNER JOIN products_cate AS b ON a.goods_cate =
b.cate_id
INNER JOIN products_brand AS c ON a.brand_name = c.brand_id;
至于连接的认证
外连接:
以左外连接为例:
A LEFT JOIN B join_condition
多少表B的结果集注重于数据表A
数码表A的结果集依据左连接条件信赖全数数据表(B表除此之外)
左外连接条件决定哪些搜索数据表B(在平素不点名WHERE条件的情景下)
若是数额表A的某条记下符合WHERE条件,可是在多少表B不设有符合连接条件的笔录,将生成三个独具列为空的额外的B行
内连接:
接纳内连接查找的笔录在连年数据表中不存在,并且在WHERE子句中尝试一下操作:column_name
IS NULL 。如果 column_name 被钦命为 NOT
NULL,MySQL将在找到适合连接着标准的笔录后终止搜索越多的行(查找争辨)

最为分类表
显示表:show clumns from 表名;
极端分类:即在同样张表中既有父类,又有子类
经过在分类表中再充实多1个字段标志其属于哪一个父类的 ID 来促成
能够经过对同一张数据表的自家连接来开展查询,供给对表标志外号

追寻显示父级id对应的称谓
select s.type_id ,s.type_name,p.type_name As parent_id from
tdb_goods_types s left join tdb_goods_types p on
s.parent_id=p.type_id;
招来子级对应的名目
select p.type_id ,p.type_name,s.type_name from tdb_goods_types p
left join tdb_goods_types s on p.type_id=s.parent_id;
检索有微微子级
select p.type_id ,p.type_name,COUNT(s.type_name) from
tdb_goods_types p left join tdb_goods_types s on
p.type_id=s.parent_id GROUP BY p.type_name ORDER BY p.type_id;
多表删除
(一)INSERT … SELECT完毕复制
INSERT tdb_goods(goods_name,cate_id,brand_id) SELECT
goods_name,cate_id,brand_id FROM tdb_goods WHERE goods_id IN
(19,20);
(二)查找重复记录
SELECT goods_id,goods_name FROM tdb_goods GROUP BY goods_name HAVING
count(goods_name) >= 2;
(三) 删除重复记录
DELETE t1 FROM tdb_goods AS t1 LEFT JOIN (SELECT goods_id,goods_name
FROM tdb_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;

delete t1 from
从···表中去除
tdb_goods as t1 left join(select goods_id,goods_name from tdb_goods
group by goods_name having count(goods_name)>=2) as t2
将tdb_goods看做t1与子查询所取得的表举办左连接
on t1.goods_name=t2.goods_name
t一和t2的接连条件
where t1.goods_id>t2.goods_id;
选出t一表中中满足t1.goods_id>t2.goods_id的

总结
子查询:出现在sq语句中的select子句,而子查询必须求出现在小括号()内,他的外层能够是select语句,insert语句,update语句,delete语句,而且在子查询中能够涵盖多个重大词:group
by ,order by ,limit以及有关函数。。。引发子查询的景色有相比较运算符
,in(NOT)in运算符,exist(NOT EXIST)引发的子查询
接连:连接分为外接连和内接连,内接连首要呈现的是左表和右表当中都合乎连接条件的笔录。外链接有分为左外连接和右外连接,左外连接显示的是左表中的全体记录和右表符合条件的笔录,右外连接和左外连接相反,mq中的select,多表更新和删除都得以用到。。内一而再,左,右连接。。
create语句中的select ,insert select 语句

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