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feat: 更新 Mysql 示例
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‎codes/mysql/SQL必知必会示例/README.md

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# 源码说明
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> 本目录代码为 [《SQL 必知必会》](https://item.jd.com/11232698.html) 部分示例源码
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> 本目录代码为 [《SQL 必知必会》](https://book.douban.com/subject/35167240/) 部分示例源码

‎codes/mysql/SQL必知必会示例/create.sql

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@@ -72,25 +72,25 @@ CREATE TABLE vendors (
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-- Define primary keys
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-- -------------------
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ALTER TABLE customers
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ADD PRIMARY KEY (cust_id);
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ADD PRIMARY KEY (cust_id);
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ALTER TABLE orderitems
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ADD PRIMARY KEY (order_num, order_item);
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ADD PRIMARY KEY (order_num, order_item);
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ALTER TABLE orders
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ADD PRIMARY KEY (order_num);
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ADD PRIMARY KEY (order_num);
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ALTER TABLE products
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ADD PRIMARY KEY (prod_id);
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ADD PRIMARY KEY (prod_id);
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ALTER TABLE vendors
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ADD PRIMARY KEY (vend_id);
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ADD PRIMARY KEY (vend_id);
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-- -------------------
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-- Define foreign keys
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-- -------------------
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ALTER TABLE orderitems
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ADD CONSTRAINT fk_orderitems_orders FOREIGN KEY (order_num) REFERENCES orders(order_num);
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ADD CONSTRAINT fk_orderitems_orders FOREIGN KEY (order_num) REFERENCES orders(order_num);
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ALTER TABLE orderitems
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ADD CONSTRAINT fk_orderitems_products FOREIGN KEY (prod_id) REFERENCES products(prod_id);
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ADD CONSTRAINT fk_orderitems_products FOREIGN KEY (prod_id) REFERENCES products(prod_id);
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ALTER TABLE orders
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ADD CONSTRAINT fk_orders_customers FOREIGN KEY (cust_id) REFERENCES customers(cust_id);
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ADD CONSTRAINT fk_orders_customers FOREIGN KEY (cust_id) REFERENCES customers(cust_id);
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ALTER TABLE products
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ADD CONSTRAINT fk_products_vendors FOREIGN KEY (vend_id) REFERENCES vendors(vend_id);
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ADD CONSTRAINT fk_products_vendors FOREIGN KEY (vend_id) REFERENCES vendors(vend_id);

‎codes/mysql/SQL必知必会示例/select.sql

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/**
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* Mysql 查询示例
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* @author Zhang Peng
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* @date 2018/5/5
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*/
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-- --------------------------------------------------------------------------------------
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-- Mysql 查询示例
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-- @author Zhang Peng
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-- @date 2018/5/5
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-- ----------------------------------------------------------------------------------------
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-- -------------------------------------------
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-- 查询数据
@@ -24,7 +24,7 @@ FROM products;
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SELECT DISTINCT vend_id
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FROM products;
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-- 限制结果
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-- 限制查询数量
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-- 返回前 5 行（1）
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SELECT *
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FROM products

‎codes/mysql/SQL性能优化/SQL函数影响索引.sql

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-- --------------------------------------------------------------------------------------
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-- 函数操作影响索引效率示例
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-- @author Zhang Peng
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-- ----------------------------------------------------------------------------------------
5+
6+
-- 步骤 1、建表
7+
CREATE TABLE tradelog (
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id INT(11) UNSIGNED NOT NULL AUTO_INCREMENT COMMENT 'Id',
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tradeid VARCHAR(32) DEFAULT NULL,
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operator INT(11) DEFAULT NULL,
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t_modified DATETIME DEFAULT NULL,
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PRIMARY KEY (id),
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KEY tradeid(tradeid),
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KEY t_modified(t_modified)
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)
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ENGINE = InnoDB
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DEFAULT CHARSET = utf8mb4;
18+
19+
CREATE TABLE trade_detail (
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id INT(11) NOT NULL,
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tradeid VARCHAR(32) DEFAULT NULL,
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trade_step INT(11) DEFAULT NULL, /* 操作步骤 */
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step_info VARCHAR(32) DEFAULT NULL, /* 步骤信息 */
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PRIMARY KEY (id),
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KEY tradeid(tradeid)
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)
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ENGINE = InnoDB
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DEFAULT CHARSET = utf8;
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-- 步骤 2、存储过程初始化数据
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INSERT INTO trade_detail
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VALUES (1, 'aaaaaaaa', 1, 'add');
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INSERT INTO trade_detail
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VALUES (2, 'aaaaaaaa', 2, 'update');
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INSERT INTO trade_detail
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VALUES (3, 'aaaaaaaa', 3, 'commit');
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INSERT INTO trade_detail
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VALUES (4, 'aaaaaaab', 1, 'add');
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INSERT INTO trade_detail
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VALUES (5, 'aaaaaaab', 2, 'update');
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INSERT INTO trade_detail
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VALUES (6, 'aaaaaaab', 3, 'update again');
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INSERT INTO trade_detail
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VALUES (7, 'aaaaaaab', 4, 'commit');
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INSERT INTO trade_detail
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VALUES (8, 'aaaaaaac', 1, 'add');
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INSERT INTO trade_detail
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VALUES (9, 'aaaaaaac', 2, 'update');
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INSERT INTO trade_detail
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VALUES (10, 'aaaaaaac', 3, 'update again');
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INSERT INTO trade_detail
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VALUES (11, 'aaaaaaac', 4, 'commit');
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55+
INSERT INTO tradelog
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VALUES (1, 'aaaaaaaa', 1000, now());
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INSERT INTO tradelog
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VALUES (2, 'aaaaaaab', 1000, now());
59+
INSERT INTO tradelog
60+
VALUES (3, 'aaaaaaac', 1000, now());
61+
62+
DELIMITER ;;
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DROP PROCEDURE IF EXISTS init;
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CREATE PROCEDURE init()
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BEGIN
66+
DECLARE i INT;
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SET i = 3;
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WHILE i < 10000
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DO
70+
INSERT INTO tradelog(tradeid, operator, t_modified)
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VALUES (concat(char(97 + (i DIV 1000)), char(97 + (i % 1000 DIV 100)), char(97 + (i % 100 DIV 10)),
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char(97 + (i % 10))), i, now());
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SET i = i + 1;
74+
END WHILE;
75+
END;;
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DELIMITER ;
77+
CALL init();
78+
79+
-- 步骤 3、执行计划查看SQL效率
80+
-- 3.1.1 此 SQL 对索引字段做函数操作，优化器会放弃走树搜索功能，改为全表扫描
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EXPLAIN
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SELECT count(*)
83+
FROM tradelog
84+
WHERE month(t_modified) = 7;
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-- 3.1.2 SQL 优化
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EXPLAIN
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SELECT count(*)
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FROM tradelog
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WHERE (t_modified >= '2016-7-1' AND t_modified < '2016-8-1') OR
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(t_modified >= '2017-7-1' AND t_modified < '2017-8-1') OR
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(t_modified >= '2018-7-1' AND t_modified < '2018-8-1');
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-- 3.2.1 此 SQL 对索引字段隐式的使用了转换函数操作，优化器会放弃走树搜索功能，改为全表扫描
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-- 相当于 select * from tradelog where CAST(tradid AS signed int) = 110717;
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EXPLAIN
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SELECT *
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FROM tradelog
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WHERE tradeid = 110717;
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-- 3.3.1 下面两条 SQL 的扫描行数不同
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-- 原因是：字符集 utf8mb4 是 utf8 的超集，所以当这两个类型的字符串在做比较的时候，
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-- MySQL 内部的操作是，先把 utf8 字符串转成 utf8mb4 字符集，再做比较。
104+
# 需要做字符编码转换
105+
EXPLAIN
106+
SELECT d.*
107+
FROM tradelog l, trade_detail d
108+
WHERE d.tradeid = l.tradeid AND l.id = 2;
109+
110+
# 上面的 SQL 等价于这条注掉的 SQL
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# SELECT *
112+
# FROM trade_detail
113+
# WHERE CONVERT(traideid USING utf8mb4) = $l2.tradeid.value;
114+
115+
# 不需要做字符编码转换
116+
EXPLAIN
117+
SELECT l.operator
118+
FROM tradelog l, trade_detail d
119+
WHERE d.tradeid = l.tradeid AND d.id = 2;

‎codes/mysql/SQL性能优化/等MDL锁.sql

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-- --------------------------------------------------------------------------------------
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-- 函数操作影响索引效率示例
3+
-- @author Zhang Peng
4+
-- ----------------------------------------------------------------------------------------
5+
6+
CREATE TABLE t (
7+
id INT(11) NOT NULL AUTO_INCREMENT COMMENT 'Id',
8+
c INT(11) DEFAULT NULL,
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PRIMARY KEY (id)
10+
)
11+
ENGINE = InnoDB;
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13+
DELIMITER ;;
14+
DROP PROCEDURE IF EXISTS init;
15+
CREATE PROCEDURE init()
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BEGIN
17+
DECLARE i INT;
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SET i = 1;
19+
WHILE(i <= 100000)
20+
DO
21+
INSERT INTO t VALUES (i, i);
22+
SET i = i + 1;
23+
END WHILE;
24+
END;;
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DELIMITER ;
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27+
CALL init();

‎codes/mysql/基本DDL示例.sql

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-- --------------------------------------------------------------------- 数据库定义
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10-
-- 撤销数据库 test
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-- 删除数据库 db_tutorial
1111
DROP DATABASE IF EXISTS db_tutorial;
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-- 创建数据库 db_tutorial
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1919
-- --------------------------------------------------------------------- 数据表定义
2020

21-
-- 撤销表 user
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-- 删除数据表 user
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DROP TABLE IF EXISTS user;
2323
DROP TABLE IF EXISTS vip_user;
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25-
-- 创建表 user
25+
-- 创建数据表 user
2626
CREATE TABLE user (
2727
id INT(10) UNSIGNED NOT NULL COMMENT 'Id',
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username VARCHAR(64) NOT NULL DEFAULT 'default' COMMENT '用户名',
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3838
-- 添加列 age
3939
ALTER TABLE user
40-
ADD age INT(3);
40+
ADD age INT(3);
4141

4242
-- 修改列 age 的类型为 tinyint
4343
ALTER TABLE user
44-
MODIFY COLUMN age TINYINT;
44+
MODIFY COLUMN age TINYINT;
4545

46-
-- 撤销列 age
46+
-- 删除列 age
4747
ALTER TABLE user
48-
DROP COLUMN age;
48+
DROP COLUMN age;
4949

5050
-- --------------------------------------------------------------------- 索引定义
5151

52-
-- 创建表 user 的索引 user_index
53-
CREATE INDEX user_index
54-
ON user(id);
52+
-- 创建表的索引
53+
CREATE INDEX idx_email
54+
ON user(email);
5555

56-
-- 创建表 user 的唯一索引 user_index2
57-
CREATE UNIQUE INDEX user_index2
58-
ON user(id);
56+
-- 创建表的唯一索引
57+
CREATE UNIQUE INDEX uniq_username
58+
ON user(username);
5959

60-
-- 撤销表 user 的索引
60+
-- 删除表 user 的索引
6161
ALTER TABLE user
62-
DROP INDEX user_index;
62+
DROP INDEX idx_email;
63+
6364
ALTER TABLE user
64-
DROP INDEX user_index2;
65+
DROP INDEX uniq_username;
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6667
-- --------------------------------------------------------------------- 视图定义
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7172
FROM user
7273
WHERE id < 10;
7374

74-
-- 撤销表 user 的视图 top_10_user_view
75+
-- 删除表 user 的视图 top_10_user_view
7576
DROP VIEW top_10_user_view;

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