sql 之 round(),trunc(),floor(),ceil()函數

 1 trunc（value,precision）按精度(precision)截取某個數字,不進行舍入操作。 2 round（value,precision）根據給定的精度(precision)輸入數值。 3 ceil (value) 產生大於或等於指定值（value）的最小整數。 4 floor（value）與 ceil（）相反，產生小於或等於指定值（value）的最小整數。 5 sign(value) 與絕對值函數ABS（）相反。ABS（）給出的是值的量而不是其符號，sign(value)則給出值的符號而不是量。 舉例如下：  trunc(11,2) = 11  trunc(-22,2) = -22  round(11,2) = 11  round(-22,2) = -22   trunc(33.33,2) = 33.33  trunc(-44.44,2) = -44.44  round(33.33,2) = 33.33  round(-44.44,2) = -44.44      trunc(55.5,2) = 55.5  trunc(-55.5,2) = -55.5

  round(55.5,2) = 55.5  round(-55.5,2) = -55.5   trunc(66.666,2) = 66.66 trunc(-77.777.5,2) = -77.77   round(66.666,2) = 66.67 round(-77.777,2) = -77.78因此只有小數位元大於精度時這兩個函數才起作用。   round(55.5) = 56   round(-55.5) = -56  trunc(55.5) = 55   trunc(-55.5) = -55  ceil(55.5) = 56    ceil(-55.5) = -55  floor(55.5) = 55   floor(-55.5) = -56  sign(146) = 1      ABS(146) = 146  sign(-30) = -1     ABS(-30) = 30  sign(0) = 0