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在MySQL中插入序号？

2024-05-16 21:40:07 517

您可以使用会话变量在MySQL中插入序号。语法如下-

SELECT @anyVariableName − = anyIntegerValue;
UPDATE yourTableName SET yourColumnName = @anyVariableName − = @anyVariableName+IncrementStep;

为了理解上述语法，让我们创建一个表。创建表的查询如下-

mysql> create table SequentialNumberDemo
   -> (
   -> SequentialNumber int not null
   -> );

使用insert命令在表中插入记录。查询如下-

mysql> insert into SequentialNumberDemo values(100);

mysql> insert into SequentialNumberDemo values(10);

mysql> insert into SequentialNumberDemo values(9);

mysql> insert into SequentialNumberDemo values(60);

mysql> insert into SequentialNumberDemo values(50);

mysql> insert into SequentialNumberDemo values(40);

使用select语句显示表中的所有记录。查询如下-

mysql> select *from SequentialNumberDemo;

以下是输出-

+------------------+
| SequentialNumber |
+------------------+
|              100 |
|               10 |
|                9 |
|               60 |
|               50 |
|               40 |
+------------------+
6 rows in set (0.00 sec)

查看上面的输出，该数字不是按顺序排列的。这是获取从1开始的序列号的查询。首先，设置序列-

mysql> select @sequence: = 0;

输出-

+---------------+
| @sequence:= 0 |
+---------------+
|             0 |
+---------------+
1 row in set (0.03 sec)

现在，查询以更新并从1开始序列-

mysql> update SequentialNumberDemo set SequentialNumber = @sequence − = @sequence+1;
Rows matched − 6 Changed − 6 Warnings − 0

再次检查表记录。查询如下-

mysql> select *from SequentialNumberDemo;

以下是输出-

+------------------+
| SequentialNumber |
+------------------+
| 1                |
| 2                |
| 3                |
| 4                |
| 5                |
| 6                |
+------------------+
6 rows in set (0.00 sec)

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在MySQL中插入序号？

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