TRUNC(x [, y])

SELECT 
    TRUNC(5555.66666, 2.1) AS 示例1,   -- 5555.66 (2.1取整為2)
    TRUNC(5555.66666, -2.6) AS 示例2,  -- 5500 (-2.6取整為-2)
    TRUNC(5555.033333) AS 示例3        -- 5555 (默認(rèn)y=0)
FROM dual;

SELECT 
    TRUNC(123.456, 1) AS 保留1位小數(shù),   -- 123.4
    TRUNC(123.456, -1) AS 截取到十位,   -- 120
    TRUNC(123.456, 0) AS 截取到整數(shù),    -- 123
    TRUNC(123.456) AS 默認(rèn)截取          -- 123
FROM dual;

-- 計算不含稅價格（直接截取2位小數(shù)）
SELECT 
    product_id,
    TRUNC(price_with_tax / 1.13, 2) AS 不含稅價格
FROM products;

-- 計算平均年齡（截取整數(shù)部分）
SELECT 
    department_id,
    TRUNC(AVG(age)) AS 平均年齡
FROM employees
GROUP BY department_id;

-- 將金額截取到百位顯示
SELECT 
    customer_id,
    TRUNC(total_amount, -2) AS 約合金額
FROM orders;

SELECT 
    TRUNC(123.456, 300) AS 超大精度,  -- 直接返回原值
    TRUNC(NULL, 2) AS 空值處理,      -- 返回NULL
    TRUNC(123.456, -300) AS 超小精度 -- 返回0
FROM dual;

SELECT 
    TRUNC(123.456, 2) AS 截取結(jié)果,    -- 123.45
    ROUND(123.456, 2) AS 舍入結(jié)果     -- 123.46
FROM dual;

SELECT 
    TRUNC(123.456, -1) AS 十位截取,   -- 120
    TRUNC(-123.456, -1) AS 負(fù)數(shù)截取   -- -120
FROM dual;