sqlite 自增列起始值和值不连续的问题

@H_502_0@一个表中只能拥有一个自增列如果多个列需要自增其它的列只能通过触发器来完成列值的自增

@H_502_0@

@H_502_0@自增列：每次都会按顺序递增，可以保证在一个表里的主键不重复该列类型为integer

@H_502_0@ 定义形式：定义形式不同生成序号的规则大方向相同也有差异各有各的优势

@H_502_0@ 1：INTEGER PRIMARY KEY AUTOINCREMENT 整形主键自增

@H_502_0@ 2：INTEGER PRIMARY KEY 整形主键

@H_502_0@

@H_502_0@seq值： sqlite数据库用来保存表中自增列中存储的最大自增值新插入的记录自增值默认为该值+1 存储在sqlite_sequence表的seq列中

@H_502_0@定义形式一：

@H_502_0@用seq列保存最大自增值自动生成的自增值为正数最小从1开始

@H_502_0@想插入0和负数的自增值必须插入时手动指定

@H_502_0@删除自增值最大那条记录或删除整个表记录时seq值不变默认新插入的自增值为seq+1

@H_502_0@

@H_502_0@插入操作：

@H_502_0@ 待插入的记录有自增列值并不为null时使用待插入的自增值插入

@H_502_0@ 待插入的记录没有自增列值或自增列值为null时

@H_502_0@ 获取seq值成功：

@H_502_0@ seq值<表中自增列最大值:让表中自增列最大值+1 赋给待插入的自增列插入

@H_502_0@ seq值>=表中自增列最大值:让seq值+1 赋给待插入的自增列插入

@H_502_0@ 获取seq值失败：用初始值1 赋给待插入的自增列插入

@H_502_0@插入结果：

@H_502_0@ 插入失败：在自增列中有待插入的自增列值

@H_502_0@ 插入成功：在自增列中没有待插入的自增列值

@H_502_0@跟新seq值：前提插入成功

@H_502_0@ 没有seq值:

@H_502_0@ 待插入的自增值<=0：seq值为0

@H_502_0@ 待插入的自增值>0：seq值为待插入的自增值

@H_502_0@ 有seq值:

@H_502_0@ 待插入的自增值<=seq值：seq值不变

@H_502_0@ 待插入的自增值>seq值：seq值为待插入的自增值

@H_502_0@

@H_502_0@delete 表操作不会修改seq值每删除一条记录会记录到事物日志中等待回滚

@H_502_0@truncate 表操作会干掉seq值事物日志中记录删除表操作不能回滚 sqlite3不支持

@H_502_0@

@H_502_0@在sqlite3中在逻辑上做到truncate操作执行以下2条语句不过效率比truncate差

@H_502_0@一：drop掉该表在重建

@H_502_0@二：1. delete from table 2.update sqlite_sequence set seq=0 where name='table' 或 delete from sqlite_sequence where name='table'

@H_502_0@经过测试2的效率比一微微微高

@H_502_0@

@H_502_0@定义形式二:

@H_502_0@不使用sqlite_sequence表seq列获取最大自增值而是获取表中自增列中的最大序号

@H_502_0@自动生成的自增值为整数（负数 0 正数）

@H_502_0@删除最大自增值那条记录或整个表记录新插入的记录的自增值还是递增值

@H_502_0@插入记录时没指定自增值：

@H_502_0@ 表中没记录：由1开始

@H_502_0@ 表中有记录：自增列中最大值+1 类似于insert into table (column1,column2) values((select max(column1) from table)+1,column2value);

@H_502_0@

@H_502_0@定义形式一：

@H_502_0@创建含有自增列的表

@H_502_0@CREATE TABLE music (id INTEGER PRIMARY KEY AUTOINCREMENT,name TEXT,author TEXT,note TEXT,ower_id INTEGER );

@H_502_0@插入若干条记录

@H_502_0@insert into music (name,author,note,ower_id) values ('aaaa',"bbb","ccc",111)

@H_502_0@insert into music (name,111)

@H_502_0@查看表中记录和seq值

@H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 1 aaaa bbb ccc 111
2 2 aaaa bbb ccc 111
3 3 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

@H_502_0@RecNo name seq
1 music 3

@H_502_0@删除自增值最大那条记录查看表中记录和seq值得知删除成功且seq值没有发送变化

@H_502_0@delete from music where id=(select max(id) from music)

@H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 1 aaaa bbb ccc 111
2 2 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq
1 music 3 @H_502_0@

插入一条新记录在看表中的记录和seq值发现表中自增列中的自增值最大那条记录自增值不是递增的

@H_502_0@insert into music (name,111)

@H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 1 aaaa bbb ccc 111
2 2 aaaa bbb ccc 111
3 4 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq
1 music 4 @H_502_0@

@H_502_0@修改seq值为200 插入一条新纪录观察表记录和seq值

@H_502_0@update sqlite_sequence set seq=200 where name='music'

@H_502_0@insert into music (name,111)

@H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 1 aaaa bbb ccc 111
2 2 aaaa bbb ccc 111
3 4 aaaa bbb ccc 111
4 201 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq
1 music 201 @H_502_0@

@H_502_0@修改seq值为100 插入一条新纪录观察表记录和seq值

@H_502_0@update sqlite_sequence set seq=100 where name='music'

@H_502_0@insert into music (name,111)

@H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 1 aaaa bbb ccc 111
2 2 aaaa bbb ccc 111
3 4 aaaa bbb ccc 111
4 201 aaaa bbb ccc 111
5 202 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq
1 music 202 @H_502_0@

@H_502_0@插入一条自增值为100的记录

@H_502_0@insert into music (id,name,ower_id) values (100,'aaaa',111)

@H_502_0@观察表记录和seq值

@H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 1 aaaa bbb ccc 111
2 2 aaaa bbb ccc 111
3 4 aaaa bbb ccc 111
4 100 aaaa bbb ccc 111
5 201 aaaa bbb ccc 111
6 202 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq
1 music 202 @H_502_0@干掉自增值最大的2条记录在插入一条新记录待插入记录自增值为101 或修改seq为100

@H_502_0@delete from music where id=(select max(id) from music)

@H_502_0@执行(

@H_502_0@update sqlite_sequence set seq=100 where name='music'

@H_502_0@insert into music (name,111)

@H_502_0@) 或insert into music (name,101)

@H_502_0@

查看表记录和seq值 @H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 1 aaaa bbb ccc 111
2 2 aaaa bbb ccc 111
3 4 aaaa bbb ccc 111
4 100 aaaa bbb ccc 111
5 101 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq
1 music 101 @H_502_0@

@H_502_0@清空整个表查看seq值

@H_502_0@select * from sqlite_sequence where name='music'

@H_502_0@RecNo name seq
1 music 101

@H_502_0@

@H_502_0@插入新记录查看表记录和seq值

@H_502_0@insert into music (name,111)

@H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 102 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq
1 music 102 @H_502_0@

@H_502_0@干掉重建表查看seq值为空表示在插入记录时id为1

@H_502_0@drop table music

@H_502_0@CREATE TABLE music (id INTEGER PRIMARY KEY AUTOINCREMENT,ower_id INTEGER );

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq
@H_502_0@插入一条id为-120的记录查看表记录和seq

@H_502_0@insert into music (id,ower_id) values (-120,111)

@H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 -120 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq
1 music 0 @H_502_0@插入一条新记录查看表记录和seq

@H_502_0@insert into music (name,111)

@H_502_0@select * from music

@H_502_0@RecNo id name author note ower_id
1 -120 aaaa bbb ccc 111
1 1 aaaa bbb ccc 111

@H_502_0@select * from sqlite_sequence where name='music'

RecNo name seq 1 music 1

sqlite 自增列 起始值和值不连续的问题

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sqlite 自增列起始值和值不连续的问题