控制列的输出长度(NUMBER类型);
SCOTT@itkaifang> SELECT * FROM dept; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang> COL deptno for 99999 SCOTT@itkaifang> SELECT * FROM dept; DEPTNO DNAME LOC ------ -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang>
控制列的输出长度(VARCHAR2类型);
SCOTT@itkaifang> SELECT * FROM dept; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang> COL deptno for 99999 SCOTT@itkaifang> SELECT * FROM dept; DEPTNO DNAME LOC ------ -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang> COL dname for a11 SCOTT@itkaifang> SELECT * FROM dept; DEPTNO DNAME LOC ------ ----------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang> COL loc for a9 SCOTT@itkaifang> SELECT * FROM dept; DEPTNO DNAME LOC ------ ----------- --------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang>
控制列名的大小写;
SCOTT@itkaifang> SELECT * FROM dept; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang> COL DEPTNO heading deptno SCOTT@itkaifang> COL DNAME heading dname SCOTT@itkaifang> COL LOC heading loc SCOTT@itkaifang> SELECT * FROM dept; deptno dname loc ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang>
隐藏指定列;
SCOTT@itkaifang> SELECT * FROM dept; deptno dname loc ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang> COL loc NOPRINT SCOTT@itkaifang> SELECT * FROM dept; deptno dname ---------- -------------- 10 ACCOUNTING 20 RESEARCH 30 SALES 40 OPERATIONS SCOTT@itkaifang> COL loc PRINT SCOTT@itkaifang> SELECT * FROM dept; deptno dname loc ---------- -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON SCOTT@itkaifang>
为列中的NULL指定默认值;
SCOTT@itkaifang> SELECT empno,ename,comm FROM emp; EMPNO ENAME COMM ---------- ---------- ---------- 7369 SMITH 7499 ALLEN 300 7521 WARD 500 7566 JONES 7654 MARTIN 1400 7698 BLAKE 7782 CLARK 7788 SCOTT 7839 KING 7844 TURNER 0 7876 ADAMS 7900 JAMES 7902 FORD 7934 MILLER 14 rows selected. SCOTT@itkaifang> COL comm NULL itkaifang SCOTT@itkaifang> SELECT empno,ename,comm FROM emp; EMPNO ENAME COMM ---------- ---------- ---------- 7369 SMITH itkaifang 7499 ALLEN 300 7521 WARD 500 7566 JONES itkaifang 7654 MARTIN 1400 7698 BLAKE itkaifang 7782 CLARK itkaifang 7788 SCOTT itkaifang 7839 KING itkaifang 7844 TURNER 0 7876 ADAMS itkaifang 7900 JAMES itkaifang 7902 FORD itkaifang 7934 MILLER itkaifang 14 rows selected. SCOTT@itkaifang>
显示指定列格式;
SCOTT@itkaifang> COL dname COLUMN DNAME ON HEADING 'dname' SCOTT@itkaifang>
清除指定列格式。
SCOTT@itkaifang> COL dname clear SCOTT@itkaifang> COL dname SP2-0046: COLUMN 'dname' not defined SCOTT@itkaifang>