sql 字符串处置函数

--wmsys.wm_concat 函数SELECT wmsys.wm_concat(ename) FROM emp WHERE deptno = 10;SELECT empno, wmsys.wm_concat(ename) OVER( ORDER BY empno,sal) FROM emp WHERE deptno  = 10;SELECT empno,wmsys.wm_concat(ename) OVER(PARTITION BY deptno) FROM emp;--NVL函数SELECT * FROM emp FOR UPDATE;--数字SELECT ename,empno,NVL(e.mgr,8888) FROM emp e;--日期SELECT empno, NVL(hiredate,SYSDATE) FROM emp;--字符串SELECT empno,NVL(ename,'simon') FROM emp;--字符控制函数SELECT LOWER(ename)  FROM emp; --小写SELECT UPPER(ename)  FROM emp; --大写SELECT INITCAP(ename)  FROM emp;--首字母大写SELECT CONCAT(ename,'-'||empno) FROM emp;--连接函数SELECT ename,SUBSTR(ename,0,3) FROM emp; --取子串SELECT ename,SUBSTR(ename,0,LENGTH(ename)-1) FROM emp; --取长度SELECT ename,INSTR(ename,'AL') AS strname FROM emp WHERE  INSTR(ename,'AL')> 0; --是否包含某子串SELECT ename,sal,LPAD(sal,10,'0') FROM emp; --从左边填充,补满10位SELECT ename,sal,RPAD(sal,10,'0') FROM emp; --从右边填充,补满10位SELECT ename,TRIM(' sdff ') FROM emp; --去除空格SELECT ename,TRIM('H' FROM 'Hello world') FROM emp; -- 从指定的字符串中去除指定的字符串