SQLServer和Oracle是大家经常用到的数据库，在此感谢作者总结出这些常用函数以供大家参考。 数学函数 1.绝对值 S:0select abs(-1) value O:0select abs(-1) value from dual 2.取整(大) S:0select ceiling(-1.001) value O:0select ceil(-1.001) value from dual 3.取整（小） S:0select floor(-1.001) value O:0select floor(-1.001) value from dual 4.取整（截取） S:0select cast(-1.002 as int) value O:0select trunc(-1.002) value from dual 5.四舍五入 S:0select round(1.23456,4) value 1.23460 O:0select round(1.23456,4) value from dual 1.2346 6.e为底的幂 S:0select Exp(1) value 2.7182818284590451 O:0select Exp(1) value from dual 2.71828182 7.取e为底的对数 S:0select log(2.7182818284590451) value 1 O:0select ln(2.7182818284590451) value from dual. 1 8.取10为底对数 S:0select log10(10) value 1 O:0select log(10,10) value from dual. 1 9.取平方 S:0select SQUARE(4) value 16 O:0select power(4,2) value from dual 16 10.取平方根 S:0select SQRT(4) value 2 O:0select SQRT(4) value from dual 2 11.求任意数为底的幂 S:0select power(3,4) value 81 O:0select power(3,4) value from dual 81 12.取随机数 S:0select rand() value O:0select sys.dbms_random.value(0,1) value from dual. 13.取符号 S:0select sign(-8) value -1 O:0select sign(-8) value from dual -1 14.圆周率 S:SELECT PI() value 3.1415926535897931 O:不知道 15.sin,cos,tan 参数都以弧度为单位 例如：0select sin(PI()/2) value 得到1（SQLServer） 16.Asin,Acos,Atan,Atan2 返回弧度 17.弧度角度互换(SQLServer，Oracle不知道) DEGREES：弧度-〉角度 RADIANS：角度-〉弧度 数值间比较 18. 求集合最大值 S:0select max(value) value from (0select 1 value union 0select -2 value union 0select 4 value union 0select 3 value)a O:0select greatest(1,-2,4,3) value from dual 19. 求集合最小值 S:0select min(value) value from (0select 1 value union 0select -2 value union 0select 4 value union 0select 3 value)a O:0select least(1,-2,4,3) value from dual 20.如何处理null值(F2中的null以10代替) S:0select F1,IsNull(F2,10) value from Tbl O:0select F1,nvl(F2,10) value from Tbl 21.求字符序号 S:0select ascii(’a’) value O:0select ascii(’a’) value from dual 22.从序号求字符 S:0select char(97) value O:0select chr(97) value from dual 23.连接 S:0select ’11’ ’22’ ’33’ value O:0select CONCAT(’11’,’22’) 33 value from dual 23.子串位置 --返回3 S:0select CHARINDEX(’s’,’sdsq’,2) value O:0select INSTR(’sdsq’,’s’,2) value from dual 23.模糊子串的位置 --返回2,参数去掉中间%则返回7 S:0select patindex(’%d%q%’,’sdsfasdqe’) value