题图：Intel Corp. President Andy Grove, right, shakes hands with Microsoft Chairman Bill Gates at a meeting in Burlingame, Ca., on Monday Nov. 9, 1992, as they team up to offer a new product of videos on personal computers.
014.科普.有生产力的Sql语句
不等不靠，有囧有料。终日乾乾，或跃在渊。
如果，我们做足了一些细节，敲出不够烂的代码，
那么，不少企业就会倒闭，信息化建设就会倒退。
如果，我们做不足一些细节，依赖于流水线。
那么，高效生产的同时，我们会退化为码工。
@史荣久 / 2015-03-27 / CC-BY-SA-3.0
观看视频
内容摘要
- 安迪-比尔定律（Andy and Bill’s Law）
- 依赖于框架流水线，我们会从手艺人退化为流水线上的码工
- 解释和部分解决Mysql的order-by-limit巨慢
- 分页问题，引申出的sublist，substring
- 一条语句，显示学生所选的课程：GROUP_CONCAT
- 各GROUP的TOP-N问题（分组内，各取前N个）
- 自增主键是个坑，尽量避免（尤其分布式）
- 大量插入(bulk insert)，VALUES
- 插入忽略：INSERT IGNORE
- 插入更新：ON DUPLICATE KEY UPDATE（有bug变的特性）
- 替换插入：REPLACE INTO
- 大量删除：DELETE & TRUNCATE（索引，事务，自增）
- 多表联合删除，子查询删除，快速删除
- 关联更新：单个字段，多个字段
- 执行计划：explain，其他优化
- 建立索引：根据sql和explain建立必要的索引
- JDBC: PreparedStatement(DML) vs Statement(DDL)
- JDBC: addBatch, executeBatch 的性能
- JDBC: allowMultiQueries,maxAllowedPacket 安全和速度
参考资源
欢迎围观
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测试SQL
select version();
-- 5.5.41-0ubuntu0.14.04.1
-- 建库
DROP DATABASE IF EXISTS `moilioincircle_r014`;
CREATE DATABASE `moilioincircle_r014`
DEFAULT CHARACTER SET utf8 COLLATE utf8_bin;
USE moilioincircle_r014;
-- 建表
DROP TABLE IF EXISTS `STUDENT`;
CREATE TABLE `STUDENT` (
`ID` int(11) NOT NULL,
`NAME` varchar(45) NOT NULL,
`GENDER` int(11) NOT NULL DEFAULT '1',
PRIMARY KEY (`ID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
DROP TABLE IF EXISTS `COURSE`;
CREATE TABLE `COURSE` (
`ID` int(11) NOT NULL,
`NAME` varchar(45) COLLATE utf8_bin NOT NULL,
PRIMARY KEY (`ID`),
UNIQUE KEY `NAME_UNIQUE` (`NAME`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
DROP TABLE IF EXISTS `STUDENT_COURSE_MAP`;
CREATE TABLE `STUDENT_COURSE_MAP` (
`STUDENT_ID` int(11) NOT NULL,
`COURSE_ID` int(11) NOT NULL,
PRIMARY KEY (`STUDENT_ID`,`COURSE_ID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
DROP TABLE IF EXISTS `EXAM`;
CREATE TABLE `EXAM` (
`STUDENT_ID` int(11) NOT NULL,
`COURSE_ID` int(11) NOT NULL,
`SCORE` int(11) NOT NULL,
PRIMARY KEY (`STUDENT_ID`,`COURSE_ID`),
KEY `IDX_SCORE` (`SCORE`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
DROP TABLE IF EXISTS `AUTOINCR`;
CREATE TABLE `AUTOINCR` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`NAME` varchar(45),
PRIMARY KEY (`ID`)
) AUTO_INCREMENT = 100
ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;
-- 数据
INSERT INTO STUDENT (ID,NAME,GENDER)
VALUES
(1,'学生1',2),
(2,'学生2',1),
(3,'学生3',NULL),
(4,'学生4',DEFAULT);
INSERT INTO COURSE (ID,NAME)
VALUES
(1,'课程1'),
(2,'课程2'),
(3,'课程3'),
(4,'课程4');
INSERT INTO STUDENT_COURSE_MAP (STUDENT_ID,COURSE_ID)
VALUES
(1,1),
(2,1),(2,2),
(3,1),(3,2),(3,3),
(4,1),(4,2),(4,3),(4,4);
INSERT INTO EXAM (STUDENT_ID,COURSE_ID,SCORE)
VALUES
(1,1,90),(1,2,70),(1,3,85),(1,4,80),
(2,1,70),(2,2,85),(2,3,75),(2,4,80),
(3,1,75),(3,2,85),(3,3,85),(3,4,65),
(4,1,60),(4,2,75),(4,3,80),(4,4,85);
INSERT INTO AUTOINCR (ID,NAME)
VALUES
(1,'自增1'),
(DEFAULT,'自增#1'),
(5,'自增5'),
(DEFAULT,'自增#2');
-- 查 -----------------
-- 学生都选了什么课（把列换成行显示）
-- set group_concat_max_len=10000;
SELECT
S.NAME,
GROUP_CONCAT(C.NAME ORDER BY C.NAME ) AS COURSES
FROM
STUDENT AS S,
COURSE AS C,
STUDENT_COURSE_MAP AS M
WHERE
S.ID = M.STUDENT_ID
AND C.ID = M.COURSE_ID
GROUP BY S.NAME
HAVING COUNT(C.NAME)>1;
-- 把各科考试，前三名取出来。
-- MYSQL 没有 ROW_NUMBER() OVER(PARTITION BY A ORDER BY B DESC)
SELECT
C.NAME AS COURSE,
S.NAME AS STUDENT,
E.SCORE
FROM
EXAM AS E ,
STUDENT AS S,
COURSE AS C
WHERE
(SELECT COUNT(*) FROM EXAM AS B
WHERE B.COURSE_ID = E.COURSE_ID
AND B.SCORE >= E.SCORE
) <= 3
AND E.STUDENT_ID = S.ID
AND E.COURSE_ID = C.ID
ORDER BY COURSE ASC, SCORE DESC;
SELECT * FROM STUDENT
WHERE (ID,NAME) IN ((1,'学生1'),(2,'学生2'));
-- ------- 增 ----------
SELECT * FROM COURSE;
INSERT IGNORE INTO COURSE (ID,NAME)
VALUES
(1,'课程1'),
(11,'课程1'),
(5,'课程5'),
(6,'课程6');
REPLACE INTO COURSE (ID,NAME)
VALUES
(5,'课程55'),
(66,'课程6'),
(7,'课程7');
INSERT INTO COURSE (ID,NAME)
VALUES (5,'课程5'),(6,'课程6'),(8,'课程6')
ON DUPLICATE KEY UPDATE
NAME=VALUES(NAME),ID=VALUES(ID);
INSERT INTO COURSE (ID,NAME)
VALUES (5,'课程5'),(6,'课程6'),(7,'课程7')
ON DUPLICATE KEY UPDATE
NAME=VALUES(NAME),
ID=(CASE WHEN NAME = VALUES(NAME)
THEN VALUES(ID)
ELSE ID
END);
-- 删
CREATE TABLE AUTOINCR_1 LIKE AUTOINCR; -- 表结构相同
INSERT INTO AUTOINCR_1 SELECT * FROM AUTOINCR;
DESCRIBE AUTOINCR_1;
CREATE TABLE AUTOINCR_2 SELECT * FROM AUTOINCR WHERE ID <10; -- 不相同
DESCRIBE AUTOINCR_2;
SELECT * FROM AUTOINCR_1;
SELECT * FROM AUTOINCR_2;
DELETE FROM AUTOINCR_1;
INSERT INTO AUTOINCR_1 (NAME) VALUES ('课程1');
TRUNCATE TABLE AUTOINCR_1;
DELETE T1,T2
FROM AUTOINCR_1 AS T1,AUTOINCR_2 AS T2
WHERE T1.ID = T2.ID;
DELETE QUICK FROM AUTOINCR_2;
OPTIMIZE TABLE AUTOINCR_2;
-- 改 ------
INSERT INTO AUTOINCR_1 SELECT ID,NULL FROM AUTOINCR;
INSERT INTO AUTOINCR_2 SELECT * FROM AUTOINCR WHERE ID <10;
-- 更新单个字段
UPDATE AUTOINCR_2 AS T2, AUTOINCR_1 AS T1
SET T1.NAME = T2.NAME
WHERE T2.ID = T1.ID;
UPDATE AUTOINCR_1 SET NAME=NULL;
UPDATE AUTOINCR_1 AS T1
SET T1.NAME = (SELECT T2.NAME FROM AUTOINCR_2 AS T2 WHERE T2.ID = T1.ID);
CREATE TABLE STUDENT_1 LIKE STUDENT;
INSERT INTO STUDENT_1 SELECT ID,CONCAT(NAME,'#'),0 FROM STUDENT;
SELECT * FROM STUDENT;
SELECT * FROM STUDENT_1;
-- 更新多个字段
UPDATE STUDENT_1 AS T1
INNER JOIN (SELECT T.ID, T.NAME, T.GENDER FROM STUDENT AS T) AS T2
ON T2.ID = T1.ID
SET T1.NAME = T2.NAME ,T1.GENDER = T2.GENDER;