ATAN¶

计算其实参的反正切值（反正切）；结果是 [-pi, pi] 区间中的数字。

语法¶

ATAN( <input_expr> )

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input_expr: The value or expression to operate on. The data type must be FLOAT or DECFLOAT.

If the input expression is of type DECFLOAT, the returned type is DECFLOAT. Otherwise, the returned type is FLOAT.

返回范围 [-pi, pi] 内以弧度（而非度数）为单位的反正切值。

SELECT ATAN(1);

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   ATAN(1)    |
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 0.7853981634 |
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