Oracle Basic1

--字符值和日期值区分大小写
SELECT * FROM AMS_SCTY_USER2 WHERE USER_ID='DSNH';
SELECT * FROM AMS_SCTY_USER2 WHERE USER_ID='dsnh';


--TO_CHAR 格式, FM/fm主要作用就是去除空格的影响。
--无空格
SELECT TO_CHAR(2020041,'FM09999999') FROM DUAL;
SELECT TO_CHAR(2020041,'fm09999999') FROM DUAL;
SELECT TO_CHAR(2020041,'fm00000000') FROM DUAL;
SELECT TO_CHAR(1,'fm00000000') FROM DUAL; 
--有空格
SELECT TO_CHAR(2020041,'09999999') FROM DUAL;

--起始非0，不补0
SELECT TO_CHAR(2020041,'FM99999999') FROM DUAL;
--日期格式
SELECT TO_CHAR(date '2020-04-10','fmDD Month YYYY') FROM DUAL;
--日期普通格式
SELECT to_char(sysdate,'yyyy-mm-dd') FROM DUAL;
--日期精简格式
SELECT to_char(sysdate,'FMyyyy-mm-dd') FROM DUAL;

--FM去空格对比
select '|'||to_char(5,'000')||'|' from dual;
select '|'||to_char(5,'FM000')||'|' from dual;