MySQL 相关项目
表
CREATE TABLE People (
last_name VARCHAR(50) NOT NULL,
first_name VARCHAR(50) NOT NULL,
dob DATE NOT NULL,
gender ENUM('m', 'f') NOT NULL,
KEY(last_name, first_name, dob)
);
EXPLAIN SELECT * FROM high_performance_mysql.People WHERE last_name LIKE 'J%';
EXPLAIN SELECT * FROM high_performance_mysql.People WHERE last_name LIKE 'A%';
为什么这两个查询语句，一个使用到了索引，一个没有使用索引？ 仅仅就是 LIKE 后面改了
CREATE TABLE People (
last_name VARCHAR(50) NOT NULL,
first_name VARCHAR(50) NOT NULL,
dob DATE NOT NULL,
gender ENUM('m', 'f') NOT NULL,
KEY(last_name, first_name, dob)
);
EXPLAIN SELECT * FROM high_performance_mysql.People WHERE last_name LIKE 'J%';
EXPLAIN SELECT * FROM high_performance_mysql.People WHERE last_name LIKE 'A%';
为什么这两个查询语句，一个使用到了索引，一个没有使用索引？ 仅仅就是 LIKE 后面改了
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