LN(y)

SELECT 
    EXP(3) AS e的三次方,          -- 返回20.0855369
    LN(20.0855369) AS 還原指數(shù),   -- 返回3
    EXP(-3) AS e的負三次方,       -- 返回0.049787068
    LN(0.049787068) AS 負指數(shù)還原 -- 返回-3
FROM dual;

SELECT 
    LN(EXP(1)) AS 驗證e,  -- 返回1
    EXP(LN(2.7182818)) AS 反向驗證 -- 返回2.7182818
FROM dual;

-- 計算投資翻倍所需時間（72法則精確版）
SELECT 
    interest_rate,
    LN(2)/LN(1 + interest_rate) AS 精確翻倍年限
FROM investment_products;

-- 對數(shù)轉(zhuǎn)換處理右偏分布
SELECT 
    user_value,
    LN(user_value + 1) AS 正態(tài)化處理值
FROM skewed_data;

-- 計算對數(shù)似然函數(shù)值
SELECT 
    SUM(LN(probability)) AS 對數(shù)似然值
FROM probability_distribution;

-- 計算需求價格彈性
SELECT 
    REGR_SLOPE(LN(quantity), LN(price))) AS 價格彈性系數(shù)
FROM sales_data;

SELECT 
    EXP(LN(15)) AS 驗證1,  -- 返回15
    LN(EXP(2.5)) AS 驗證2  -- 返回2.5
FROM dual;

-- 換底公式：LN(y) = LOG(x,y) * LN(x)
SELECT 
    LN(100) AS 自然對數(shù),
    LOG(10,100) * LN(10) AS 換底結(jié)果
FROM dual;

SELECT 
    LN(10) AS 自然對數(shù),
    LOG(10,10) AS 常用對數(shù),
    LOG(2,10) AS 二進制對數(shù)
FROM dual;

SELECT 
    LN(0) AS 零值測試,      -- 報錯：ORA-01428
    LN(-5) AS 負值測試,     -- 報錯：ORA-01428
    LN(NULL) AS 空值測試    -- 返回NULL
FROM dual;

-- 創(chuàng)建函數(shù)索引加速查詢
CREATE INDEX idx_ln_salary ON employees(LN(salary + 1));

-- 物化視圖預(yù)計算結(jié)果
CREATE MATERIALIZED VIEW mv_ln_values
REFRESH COMPLETE
AS SELECT id, LN(value) AS ln_value FROM source_data;

-- 使用BINARY_DOUBLE提高精度
SELECT 
    LN(BINARY_DOUBLE '1234.5678') AS 高精度結(jié)果
FROM dual;