如果TABLE的某一项具有AUTO_INCREMENT属性,则这一项必须用PRIMARY KEY或者KEY修饰,如果插入时给某一记录中的这一栏赋值一个常数,那么在下一次插入时省略此项,则自动保存的是上一项加1,也就是整个序列未必是正整数由小到大的顺序,AUTO_INCREMENT项必须为整数,如果是FLOAT,则小数部分一定为0,使用AUTO_INCREMENT时,如果相应的某一条记录写入失败,编号也会分配,即下一条成功写入的自动编号会再次加一
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主键约束的字段禁止为空
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如果一个有AUTO_INCREMENT 的字段的表中插入了若干记录,当把这个表中的记录全部删掉后,再次添加记录,记录不会从1开始编号,而是从已删除编号的最大值加1开始编
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MYSQL学习过程中遇到的生疏点,记录在此,以供复习
最新推荐文章于 2024-12-03 10:31:25 发布