COL FIRST_NAME FORMAT A15

 

题:在多表格查询中下列语法是什么意思啊？？？
SQL>   COL FIRST_NAME FORMAT A15
SQL>   COL LAST_NAME FORMAT A15
SQL>   COL DEPARTMENT_NAME FORMAT A15
SQL>   COL CITY FORMAT A15
请问在这里COL起什么作用？？？
FORMAT A15是什么意思阿？？？
回答:col就是column的缩写，FORMAT A15是设置对应的列宽度，A15就是宽度为15个字符。
COL命令：
主要格式化列的显示形式。
该命令有许多选项，具体如下：
COL[UMN] [{ column|expr} [ option ...]]
Option选项可以是如下的子句:
ALI[AS] alias
CLE[AR]
FOLD_A[FTER]
FOLD_B[EFORE]
FOR[MAT] format
HEA[DING] text
JUS[TIFY] {L[EFT]|C[ENTER]|C[ENTRE]|R[IGHT]}
LIKE { expr|alias}
NEWL[INE]
NEW_V[ALUE] variable
NOPRI[NT]|PRI[NT]
NUL[L] text
OLD_V[ALUE] variable
ON|OFF
WRA[PPED]|WOR[D_WRAPPED]|TRU[NCATED]
 
1). 改变缺省的列标题
COLUMN column_name HEADING column_heading
For example:
Sql>select * from dept;
     DEPTNO DNAME                        LOC
---------- ---------------------------- ---------
         10 ACCOUNTING                   NEW YORK
sql>col  LOC heading location
sql>select * from dept;
    DEPTNO DNAME                        location
--------- ---------------------------- -----------
        10 ACCOUNTING                   NEW YORK
 
2). 将列名ENAME改为新列名EMPLOYEE NAME并将新列名放在两行上：
Sql>select * from emp
Department  name           Salary
---------- ---------- ----------
         10 aaa                11        
SQL> COLUMN ENAME HEADING ’Employee|Name’
Sql>select * from emp
            Employee
Department  name           Salary
---------- ---------- ---------- 
         10 aaa                11
note: the col heading turn into two lines from one line.
 
3). 改变列的显示长度：
FOR[MAT] format
Sql>select empno,ename,job from emp;
      EMPNO ENAME      JOB       
---------- ----------     ---------
       7369 SMITH      CLERK     
       7499 ALLEN      SALESMAN  
7521 WARD       SALESMAN  
Sql> col ename format a40
      EMPNO ENAME                                    JOB
----------   ----------------------------------------         ---------
       7369 SMITH                                    CLERK
       7499 ALLEN                                    SALESMAN
       7521 WARD                                    SALESMAN
 
4). 设置列标题的对齐方式
JUS[TIFY] {L[EFT]|C[ENTER]|C[ENTRE]|R[IGHT]}
SQL> col ename justify center
SQL> /
      EMPNO           ENAME                   JOB
----------   ----------------------------------------       ---------
       7369 SMITH                                    CLERK
       7499 ALLEN                                    SALESMAN
7521 WARD                                     SALESMAN
对于NUMBER型的列，列标题缺省在右边，其它类型的列标题缺省在左边
 
5). 不让一个列显示在屏幕上
NOPRI[NT]|PRI[NT]
SQL> col job noprint
SQL> /
      EMPNO           ENAME
----------     ----------------------------------------
       7369 SMITH
       7499 ALLEN
7521 WARD
 
6). 格式化NUMBER类型列的显示：
SQL> COLUMN SAL FORMAT $99,990
SQL> /
Employee
Department Name        Salary    Commission
---------- ---------- --------- ----------
30          ALLEN        $1,600    300
 
7). 显示列值时，如果列值为NULL值，用text值代替NULL值
COMM NUL[L] text
SQL>COL COMM NUL[L] text
 
8). 设置一个列的回绕方式
WRA[PPED]|WOR[D_WRAPPED]|TRU[NCATED]
        COL1
--------------------
HOW ARE YOU?
 
SQL>COL COL1 FORMAT A5
SQL>COL COL1 WRAPPED
COL1
-----
HOW A
RE YO
U?
 
SQL> COL COL1 WORD_WRAPPED
COL1
-----
HOW
ARE
YOU?
 
SQL> COL COL1 WORD_WRAPPED
COL1
-----
HOW A