MySQL 操作數據表記錄
INSERT插入記錄
INSERT [INTO] tb_name [(col_name),…] {VALUES| VALUE}
({expr | DEFAULT},…),(…),…
INSERT [INTO] tb_name SET col_name={expr |DEFAULT},…
INSERT [INTO] tb_name [(col_name)] SELECT …
此方法可以將查詢結果插入到指定數據表。
UPDATE
單表更新
UPDATE [LOW_PRIORITY] [IGNORE]table_reference SET col_name1 = {expr1 |DEFAULT}
[, col_name2 = {expr2 | DEFAULT}] ……
[WHERE where_condition]
DELETE
單表刪除
DELETE FROM tb_name [WHERE where_condition]
SELECT
查找記錄
SELECT select_expr[,select_expr ….]
[
FROMtable_references
[WHERE where_condition ]
[GROUPBY {col_name | position} [ASC | DESC],….]
[HAVINGwhere_condition]
[ORDERBY {col_name | expr | position} [ASC | DESC],…]
[LIMIT{[offset,] row_count | row_count OFFSET offset}]
]
字段賦予別名
SELECT 字段名 AS 別名
使用where條件過濾
對查詢結果分組
[GROUP BY{col_name | position} [ASC |DESC],...] ASC 默認的升序
[HAVING ] 分組條件,分組條件要麼用聚合函數(COUNT()、AVG() 只有一個返回值),或者字段必須出現在 select的字段裏。
對查詢結果進行排序
[ORDER BY{col_name | expr |position} [ASC |DESC],…]
LIMIT
限制返回結果的數量
[LIMIT{[offset,]row_count |row_count OFFSEToffset}]
子查詢
子查詢(Subquery)是指出現在其他SQL語句內的SELECT子句。
子查詢指嵌套在查詢內部,且必須時鐘出現在圓括號內。
子查詢可以包含多個關鍵字或條件,
如DISTINCT /GROUP BY / ORDER BY / LIMIT 函數等。
子查詢的外層查詢可以是SELECT , INSERT,UPDATE,SET 或 DO。
子查詢可以返回標量、一行、一列或子查詢。
例如:
SELECT * FROM t1 WHERE col1 = (SELECT col2FROM t2);
其中SELECT * FROM t1,稱爲 Quter Query / Outer Statement
SELECT col2 FROM t2,稱爲SubQuery
子查詢分類
1. 使用比較運算符的子查詢
使用比較運算符的子查詢
= / > / < / >= / <= / <> / != / <=>
用ANY、SOME、ALL修飾的比較運算符
Operand comparison_operator ANY (subquery)
Operand comparison_operator SOME(subquery)
Operand comparison_operator ALL(subquery)
1. 使用 [NOT] IN 的子查詢
Operand comparison_operator [NOT] IN (subquery)
=ANY 運算符與IN等效。
!= ALL 或 <> ALL 運算符與NOT IN 等效。
2. 使用[NOT] EXISTS的子查詢
如果子查詢返回任何行,EXISTS將返回TRUE; 否則爲FALSE.
多表更新
UPDATE table_references
SET col_name1 = {expr1 | DEFAULT}
[,col_name2 = {expr2 |DEFAULT}]…
[WHERE where_condition]
CREATE… SELECT
創建數據表同時將查詢結果寫入到數據表
CREATE TABLE [IF NOT EXISTS] tb_name
[(create_definition,…)]
Select_statement
連接
使用ON關鍵字來設定連接的條件,也可以使用WHERE來代替。
通常使用ON關鍵字來設定連接條件,
使用WHERE關鍵字進行結果集記錄的過濾。
內連接
顯示左表及右表符合連接條件的記錄
左外連接
顯示左表的全部記錄及右表符合連接條件的記錄
自身連接
數據表連接自己。
例:(本例來自慕課網http://www.imooc.com/video/2398)
1.子查詢是指在另一個查詢語句中的SELECT子句。
例句:
SELECT * FROM t1 WHERE column1 = (SELECTcolumn1 FROM t2);
其中,SELECT * FROM t1...稱爲Outer Query[外查詢](或者Outer Statement),
SELECT column1 FROM t2 稱爲Sub Query[子查詢]。
所以,我們說子查詢是嵌套在外查詢內部。而事實上它有可能在子查詢內部再嵌套子查詢。
子查詢必須出現在圓括號之間。
行級子查詢
SELECT * FROM t1 WHERE (col1,col2) = (SELECTcol3, col4 FROM t2 WHERE id = 10);
SELECT * FROM t1 WHERE ROW(col1,col2) =(SELECT col3, col4 FROM t2 WHERE id = 10);
行級子查詢的返回結果最多爲一行。
優化子查詢
-- 創建數據表
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 NULLDEFAULT 0,
is_show BOOLEAN NOT NULL DEFAULT 1,
is_saleoff BOOLEAN NOT NULL DEFAULT 0
);
-- 寫入記錄
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('R510VC15.6英寸筆記本','筆記本','華碩','3399',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Y400N14.0英寸筆記本電腦','筆記本','聯想','4899',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)VALUES('G150TH 15.6英寸遊戲本','遊戲本','雷神','8499',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)VALUES('X550CC 15.6英寸筆記本','筆記本','華碩','2799',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)VALUES('X240(20ALA0EYCD) 12.5英寸超極本','超級本','聯想','4999',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('U330P13.3英寸超極本','超級本','聯想','4299',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)VALUES('SVP13226SCB 13.3英寸觸控超極本','超級本','索尼','7999',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iPadmini MD531CH/A 7.9英寸平板電腦','平板電腦','蘋果','1998',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iPadAir MD788CH/A 9.7英寸平板電腦(16G WiFi版)','平板電腦','蘋果','3388',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' iPadmini ME279CH/A 配備 Retina 顯示屏 7.9英寸平板電腦(16G WiFi版)','平板電腦','蘋果','2788',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)VALUES('IdeaCentre C340 20英寸一體電腦 ','臺式機','聯想','3499',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)VALUES('Vostro 3800-R1206 臺式電腦','臺式機','戴爾','2899',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('iMacME086CH/A 21.5英寸一體電腦','臺式機','蘋果','9188',DEFAULT,DEFAULT);
INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)VALUES('AT7-7414LP 臺式電腦(i5-3450四核 4G 500G 2G獨顯 DVD 鍵鼠 Linux )','臺式機','宏碁','3699',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)VALUES('Z220SFF F4F06PA工作站','服務器/工作站','惠普','4288',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff)VALUES('PowerEdge T110 II服務器','服務器/工作站','戴爾','5388',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('MacPro MD878CH/A 專業級臺式電腦','服務器/工作站','蘋果','28888',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('HMZ-T3W 頭戴顯示設備','筆記本配件','索尼','6999',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('商務雙肩揹包','筆記本配件','索尼','99',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('X3250M4機架式服務器 2583i14','服務器/工作站','IBM','6888',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('玄龍精英版 筆記本散熱器','筆記本配件','九州風神','',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('HMZ-T3W 頭戴顯示設備','筆記本配件','索尼','6999',DEFAULT,DEFAULT);
INSERT tdb_goods(goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('商務雙肩揹包','筆記本配件','索尼','99',DEFAULT,DEFAULT);
-- 求所有電腦產品的平均價格,並且保留兩位小數,AVG,MAX,MIN、COUNT、SUM爲聚合函數
SELECT ROUND(AVG(goods_price),2) ASavg_price FROM tdb_goods;
-- 查詢所有價格大於平均價格的商品,並且按價格降序排序
SELECT goods_id,goods_name,goods_price FROMtdb_goods WHERE goods_price > 5845.10 ORDER BY goods_price DESC;
-- 使用子查詢來實現
SELECT goods_id,goods_name,goods_price FROMtdb_goods
WHERE goods_price > (SELECTROUND(AVG(goods_price),2) AS avg_price FROM tdb_goods)
ORDER BY goods_price DESC;
-- 查詢類型爲“超記本”的商品價格
SELECT goods_price FROM tdb_goods WHEREgoods_cate = '超級本';
-- 查詢價格大於或等於"超級本"價格的商品,並且按價格降序排列
SELECT goods_id,goods_name,goods_price FROMtdb_goods
WHERE goods_price = ANY(SELECT goods_priceFROM tdb_goods WHERE goods_cate = '超級本')
ORDER BY goods_price DESC;
-- = ANY或 = SOME 等價於 IN
SELECT goods_id,goods_name,goods_price FROMtdb_goods
WHERE goods_price IN (SELECT goods_priceFROM tdb_goods WHERE goods_cate = '超級本')
ORDER BY goods_price DESC;
-- 創建“商品分類”表
CREATE TABLE IF NOT EXISTS tdb_goods_cates(
cate_id SMALLINT UNSIGNED PRIMARY KEYAUTO_INCREMENT,
cate_name VARCHAR(40)
);
-- 查詢tdb_goods表的所有記錄,並且按"類別"分組
SELECT goods_cate FROM tdb_goods GROUP BYgoods_cate;
-- 將分組結果寫入到tdb_goods_cates數據表
INSERT tdb_goods_cates (cate_name) SELECTgoods_cate FROM tdb_goods GROUP BY goods_cate;
-- 通過tdb_goods_cates數據表來更新tdb_goods表
UPDATE tdb_goods INNER JOIN tdb_goods_catesON goods_cate = cate_name
SET goods_cate = cate_id ;
-- 通過CREATE...SELECT來創建數據表並且同時寫入記錄
-- SELECT brand_name FROM tdb_goods GROUP BYbrand_name;
CREATE TABLE tdb_goods_brands (
brand_id SMALLINT UNSIGNED PRIMARY KEYAUTO_INCREMENT,
brand_name VARCHAR(40) NOT NULL
) SELECT brand_name FROM tdb_goods GROUP BYbrand_name;
-- 通過tdb_goods_brands數據表來更新tdb_goods數據表(錯誤)
UPDATE tdb_goods INNER JOIN tdb_goods_brands ON brand_name =brand_name
SET brand_name = brand_id;
-- Column 'brand_name' in field list isambigous
-- 正確
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的數據表結構
DESC tdb_goods;
-- 通過ALTER TABLE語句修改數據表結構
ALTER TABLE tdb_goods
CHANGE goods_cate cate_id SMALLINT UNSIGNEDNOT NULL,
CHANGE brand_name brand_id SMALLINT UNSIGNEDNOT NULL;
-- 分別在tdb_goods_cates和tdb_goods_brands表插入記錄
INSERT tdb_goods_cates(cate_name) VALUES('路由器'),('交換機'),('網卡');
INSERT tdb_goods_brands(brand_name) VALUES('海爾'),('清華同方'),('神舟');
-- 在tdb_goods數據表寫入任意記錄
INSERTtdb_goods(goods_name,cate_id,brand_id,goods_price) VALUES(' LaserJet ProP1606dn 黑白激光打印機','12','4','1849');
-- 查詢所有商品的詳細信息(通過內連接實現)
SELECTgoods_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 ONg.brand_id = b.brand_id\G;
-- 查詢所有商品的詳細信息(通過左外連接實現)
SELECT goods_id,goods_name,cate_name,brand_name,goods_priceFROM 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 ONg.brand_id = b.brand_id\G;
-- 查詢所有商品的詳細信息(通過右外連接實現)
SELECT goods_id,goods_name,cate_name,brand_name,goods_priceFROM 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 ONg.brand_id = b.brand_id\G;
-- 無限分類的數據表設計
CREATE TABLE tdb_goods_types(
type_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
type_name VARCHAR(20) NOT NULL,
parent_id SMALLINT UNSIGNED NOT NULLDEFAULT 0
);
INSERT tdb_goods_types(type_name,parent_id)VALUES('家用電器',DEFAULT);
INSERT tdb_goods_types(type_name,parent_id)VALUES('電腦、辦公',DEFAULT);
INSERT tdb_goods_types(type_name,parent_id)VALUES('大家電',1);
INSERT tdb_goods_types(type_name,parent_id)VALUES('生活電器',1);
INSERT tdb_goods_types(type_name,parent_id)VALUES('平板電視',3);
INSERT tdb_goods_types(type_name,parent_id)VALUES('空調',3);
INSERT tdb_goods_types(type_name,parent_id)VALUES('電風扇',4);
INSERT tdb_goods_types(type_name,parent_id)VALUES('飲水機',4);
INSERT tdb_goods_types(type_name,parent_id)VALUES('電腦整機',2);
INSERT tdb_goods_types(type_name,parent_id)VALUES('電腦配件',2);
INSERT tdb_goods_types(type_name,parent_id)VALUES('筆記本',9);
INSERT tdb_goods_types(type_name,parent_id)VALUES('超級本',9);
INSERT tdb_goods_types(type_name,parent_id)VALUES('遊戲本',9);
INSERT tdb_goods_types(type_name,parent_id)VALUES('CPU',10);
INSERT tdb_goods_types(type_name,parent_id)VALUES('主機',10);
-- 查找所有分類及其父類
SELECTs.type_id,s.type_name,p.type_name
FROMtdb_goods_types AS s LEFT JOIN tdb_goods_types AS p
ONs.parent_id = p.type_id;
-- 查找所有分類及其子類
SELECTp.type_id,p.type_name,s.type_name
FROMtdb_goods_types AS p LEFT JOIN tdb_goods_types AS s
ONs.parent_id = p.type_id;
-- 查找所有分類及其子類的數目
SELECTp.type_id,p.type_name,count(s.type_name) AS children_count
FROMtdb_goods_types AS p LEFT JOIN tdb_goods_types AS s
ONs.parent_id = p.type_id
GROUP BYp.type_name
ORDER BYp.type_id;
-- 爲tdb_goods_types添加child_count字段
ALTERTABLE tdb_goods_types ADD child_count MEDIUMINT UNSIGNED NOT NULL DEFAULT 0;
-- 將剛纔查詢到的子類數量更新到tdb_goods_types數據表
UPDATEtdb_goods_types AS t1 INNER JOIN
( SELECTp.type_id,p.type_name,count(s.type_name) AS children_count
FROMtdb_goods_types AS p
LEFTJOIN tdb_goods_types AS s ON s.parent_id = p.type_id
GROUP BYp.type_name
ORDER BYp.type_id ) AS t2
ON t1.type_id = t2.type_id
SETt1.child_count = t2.children_count;
-- 複製編號爲12,20的兩條記錄
SELECT * FROM tdb_goods WHERE goods_id IN(19,20);
--INSERT ... SELECT實現複製
INSERTtdb_goods(goods_name,cate_id,brand_id)
SELECTgoods_name,cate_id,brand_id
FROMtdb_goods
WHEREgoods_id IN (19,20);
-- 查找重複記錄
SELECTgoods_id,goods_name
FROMtdb_goods
GROUP BYgoods_name
HAVINGcount(goods_name) >= 2;
-- 刪除重複記錄
DELETEt1 FROM tdb_goods AS t1
LEFTJOIN (SELECT goods_id,goods_name FROM tdb_goods GROUP BY goods_name
HAVINGcount(goods_name) >= 2 ) AS t2
ONt1.goods_name = t2.goods_name
WHEREt1.goods_id > t2.goods_id;