# swoole_table->decr
原子自减操作。
~~~
function swoole_table->decr(string $key, string $column, mixed $decrby = 1);
~~~
- $key 指定数据的key，如果$key对应的行不存在，默认列的值为0
- $column 指定列名，仅支持浮点型和整型字段
- $decrby 减量，默认为1。如果列为整形，$decrby必须为int型，如果列为浮点型，$decrby必须为float类型
- 失败返回false，成功返回最终的结果数值
> swoole_table->decr在1.7.15以上版本可用
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