45 lines
1.3 KiB
MySQL
45 lines
1.3 KiB
MySQL
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DROP table if Exists kid_score ;
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create table kid_score(
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id tinyint unsigned not null,
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birth_day date not null,
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score int unsigned not null,
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primary key(id, birth_day) -- 唯一索引是由 id + birth_day 两个字段组成
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) engine = InnoDB;
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-- 初始化数据
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insert into kid_score(id, birth_day, score) values (1,'2019-01-15',10),(2,'2019-01-16',20);
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-- 如果你插入的记录导致一个UNIQUE索引或者primary key(主键)出现重复，那么就会认为该条记录存在，
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-- 则执行update语句而不是insert语句，
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-- 反之，则执行insert语句而不是更新语句。
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-- 1. 唯一索引重复
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insert into kid_score(id, birth_day, score)
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values (1,'2019-01-15',30) ON DUPLICATE KEY UPDATE score = score + 50;
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-- 2. 唯一索引不重复
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insert into kid_score(id, birth_day, score)
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values (2,'2019-01-15',30) ON DUPLICATE KEY UPDATE score = score + 50;
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-- 3. 唯一索引重复，插入完全相同数据
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insert into kid_score(id, birth_day, score)
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values (2,'2019-01-16',20) ON DUPLICATE KEY UPDATE score = 20;
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-- 4. 影响行数
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-- 需要注意的是：如果行作为新记录被插入，则受影响行的值为1；如果原有的记录被更新，则受影响行的值为2，
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-- 如果更新的数据和已有的数据一模一样，则受影响的行数是0。
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Select * From kid_score ;
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