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t sign(-2) from tb_stu; --正数返1 负数返-1 0返0
select trunc(12.232323123,5) from tb_stu;--取5位小数
select round(1232.343,2) from tb_stu;--小数位为2 四舍五入
select exp(3) from tb_stu; --求指数
select mod(12,8) from tb_stu; --求余数
select ln(10) from tb_stu;--自然对数
select log(10,100) from tb_stu;--以10为底 100的对数
select vsize(1010) from tb_stu;--返回1010所占空间的大小
8 常用的函数
select initcap(stu_name) from tb_stu;--首字符转换成大写
select stu_name,instr(stu_name,'s') from tb_stu;--查找s在stu_name中的位置 返回相应的值(0 n)
select length(stu_name) from tb_stu;--返回长度
select upper(stu_name) from tb_stu;--换大写
select lower(stu_name) from tb_stu;--换小写
select lpad(stu_name,11,'Hello') from tb_stu;--长度不够则在左边填充Hello 直到够11
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