create table tb_sequence(id int auto_increment not null ,primary key(id) );
insert into tb_sequence values(),(),(),(),(),(),(),(),(),(),(),(),();
insert into tb_sequence values(),(),(),(),(),(),(),(),(),(),(),(),();
2016-08-05
刪除重復(fù)行，并保留id最大的：
DELETE a
FROM user1_test a JOIN
(SELECT user_name, COUNT(*), MAX(id) AS id FROM user1_test GROUP BY user_name HAVING COUNT(*)>1) b
ON a.user_name = b.user_name
WHERE a.id < b.id;
DELETE a
FROM user1_test a JOIN
(SELECT user_name, COUNT(*), MAX(id) AS id FROM user1_test GROUP BY user_name HAVING COUNT(*)>1) b
ON a.user_name = b.user_name
WHERE a.id < b.id;
2016-07-29
SELECT user_name, 'arms' AS equipment, arms FROM user1 a JOIN user1_equipment b ON a.id = b.user_id
UNION ALL
SELECT user_name, 'clothing' AS equipment, arms FROM user1 a JOIN user1_equipment b ON ...
UNION ALL
SELECT user_name, 'shoe' AS equipment, arms FROM user1 a JOIN user1_equipment b ON ...
UNION ALL
SELECT user_name, 'clothing' AS equipment, arms FROM user1 a JOIN user1_equipment b ON ...
UNION ALL
SELECT user_name, 'shoe' AS equipment, arms FROM user1 a JOIN user1_equipment b ON ...
2016-07-28
SELECT user_name, arms, clothing, shoe FROM user1 a JOIN user1_equipment b ON a.id = b.user_id;
2016-07-28
INSERT INTO user1_equipment VALUES (NULL, 3, '金箍棒', '梭子黃金甲', '藕絲步云履');
INSERT INTO user1_equipment VALUES (NULL, 2, '九齒釘耙', '僧衣', '僧鞋');
INSERT INTO user1_equipment VALUES (NULL, 4, '降妖寶杖', '僧衣', '僧鞋');
INSERT INTO user1_equipment VALUES (NULL, 1, '九環(huán)錫杖', '錦斕袈裟', '僧鞋');
INSERT INTO user1_equipment VALUES (NULL, 2, '九齒釘耙', '僧衣', '僧鞋');
INSERT INTO user1_equipment VALUES (NULL, 4, '降妖寶杖', '僧衣', '僧鞋');
INSERT INTO user1_equipment VALUES (NULL, 1, '九環(huán)錫杖', '錦斕袈裟', '僧鞋');
2016-07-28
CREATE TABLE user1_equipment (
id TINYINT UNSIGNED AUTO_INCREMENT NOT NULL,
user_id SMALLINT UNSIGNED,
arms VARCHAR(10) CHARACTER SET utf8 DEFAULT NULL,
clothing VARCHAR(10) CHARACTER SET utf8 DEFAULT NULL,
shoe VARCHAR(10) CHARACTER SET utf8 DEFAULT NULL,
PRIMARY KEY(id)
);
id TINYINT UNSIGNED AUTO_INCREMENT NOT NULL,
user_id SMALLINT UNSIGNED,
arms VARCHAR(10) CHARACTER SET utf8 DEFAULT NULL,
clothing VARCHAR(10) CHARACTER SET utf8 DEFAULT NULL,
shoe VARCHAR(10) CHARACTER SET utf8 DEFAULT NULL,
PRIMARY KEY(id)
);
2016-07-28
老師，我覺(jué)得這種如果開(kāi)發(fā)中是不是應(yīng)該交給程序去進(jìn)行，分割字符串感覺(jué)效率會(huì)更高
2016-07-26
并沒(méi)有懂，這個(gè)操作以后是修改了原表還是生成了一張臨時(shí)的表啊
2016-07-21
回復(fù)前面同時(shí)后來(lái)人估計(jì)也會(huì)有的疑問(wèn)：我難道只能一行行寫？回答是：這是開(kāi)發(fā)技巧！如果你有幾百行幾百列的數(shù)據(jù)要行列轉(zhuǎn)換，那不叫開(kāi)發(fā)叫維護(hù)，至于怎么維護(hù)……你問(wèn)我？我告訴你，導(dǎo)出成excel不就行了么，然而導(dǎo)出不是開(kāi)發(fā)時(shí)的主要問(wèn)題了
2016-07-18
最新回答 / qq__2964
這是理想狀態(tài)，一般一個(gè)程序?qū)懞昧?，基本都不?huì)去怎么修改了，除了客戶強(qiáng)烈要求修改業(yè)務(wù)外（不改不付錢啊這些），開(kāi)發(fā)基本不會(huì)動(dòng)程序，都是讓實(shí)施人員從數(shù)據(jù)庫(kù)中動(dòng)刀子，這就是現(xiàn)狀，讓你加過(guò)程啊，做報(bào)表啊。。。
