a908773042的专栏

1，字符串处理 Lower转换小写upper转换大写substr取子串length取长度trim去空格2，类型转换 to_date将字符串转换成日期to_char...

Round()ROUND和TRUNC按照指定的精度进行舍入SQL> select round(55.5),round(-55.4),trunc(55.5),trunc(-55.5) from dual;ROUND(55.5) ROUND(-55.4) TRUNC(55.5) TRUNC(-55.5)----------- ------------ ----------...

Sysdate用来得到系统的当前日期select sysdate from dual