索引创建、删除与使用:
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create方式创建索引:
建表时创建索引CREATE TABLE IF NOT EXISTS user_info_vip ( id INT PRIMARY KEY AUTO_INCREMENT COMMENT '自增ID', uid INT UNIQUE NOT NULL COMMENT '用户ID', nick_name VARCHAR(64) COMMENT '昵称', achievement INT DEFAULT 0 COMMENT '成就值', level INt COMMENT '用户等级', job VARCHAR(32) COMMENT '职业方向' , register_time datetime COMMENT '注册时间' DEFAULT CURRENT_TIMESTAMP ) CHARACTER SET utf8 COLLATE utf8_general_ci;
单独创建索引
CREATE INDEX idx_duration ON examination_info ( duration ); -- 普通索引 CREATE UNIQUE INDEX uniq_idx_exam_id ON examination_info ( exam_id ); --唯一索引 CREATE FULLTEXT INDEX full_idx_tag ON examination_info ( tag ); -- 全文索引
alter 创建索引
ALTER TABLE examination_info ADD INDEX `idx_duration` ( `duration` ), ADD UNIQUE INDEX `uniq_idx_exam_id` ( `exam_id` ), ADD FULLTEXT INDEX `full_idx_tag` ( `tag` ); ```
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删除索引
drop方式删除索引:DROP INDEX <索引名> ON <表名>
index前面不需要再说明是否是unique,或者full等。DROP INDEX idx_duration on examination_info; DROP INDEX uniq_idx_exam_id on examination_info; DROP INDEX full_idx_tag on examination_info;
alter方式删除索引:ALTER TABLE <表名> DROP INDEX <索引名>
ALTER TABLE examination_info DROP INDEX `idx_duration`; ALTER TABLE examination_info DROP INDEX `uniq_idx_exam_id`; ALTER TABLE examination_info DROP INDEX `full_idx_tag`;
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查看索引
SHOW INDEX FROM <表名> [ FROM <数据库名>]SHOW INDEX FROM examination_info FROM mytest;