Oracle ALIAS

 執行以下query

SELECT ENAME , SAL , COMM

FROM EMP;

ENAME	SAL	COMM
KING	5000	-
BLAKE	2850	-
CLARK	2450	-
JONES	2975	-
SCOTT	3000	-
FORD	3000	-
SMITH	800	-
ALLEN	1600	300
WARD	1250	500
MARTIN	1250	1400

但看ENAME , SAL , COMM 不夠直觀,

可以改成以下query:

SELECT ENAME EMPLOYEENAME, SAL SALARY, COMM COMMISSION

FROM EMP;

EMPLOYEENAME	SALARY	COMMISSION
KING	5000	-
BLAKE	2850	-
CLARK	2450	-
JONES	2975	-
SCOTT	3000	-
FORD	3000	-
SMITH	800	-
ALLEN	1600	300
WARD	1250	500
MARTIN	1250	1400

這樣看欄位名稱比較容易看懂

另外這樣子的寫法中間不允許空格

SELECT ENAME EMPLOYEE NAME, SAL SALARY, COMM COMMISSION

FROM EMP;

Oracle會直接報錯誤

如果想要讓欄位呈現中間是空格的話要修改成這樣:

SELECT ENAME "EMPLOYEE NAME", SAL SALARY, COMM COMMISSION

FROM EMP;

EMPLOYEE NAME	SALARY	COMMISSION
KING	5000	-
BLAKE	2850	-
CLARK	2450	-
JONES	2975	-
SCOTT	3000	-
FORD	3000	-
SMITH	800	-
ALLEN	1600	300
WARD	1250	500
MARTIN	1250	1400

這樣就看的到差異了

此外也可以使用AS

SELECT 

ENAME AS "EMPLOYEE NAME", 

SAL AS SALARY, 

COMM COMMISSION

FROM EMP;

會得到一樣的結果

EMPLOYEE NAME	SALARY	COMMISSION

也可以加入字串

如以下query

SELECT 'hello my name is ' || ename as "concatenated value"

FROM EMP

WHERE job = 'MANAGER'

concatenated value
hello my name is BLAKE
hello my name is CLARK
hello my name is JONES

修改一下query

SELECT  'Hello, I am ' || ename || ' , I make $' || sal || ' per month' as "employee income"

FROM EMP

employee income
Hello, I am KING , I make $5000 per month
Hello, I am BLAKE , I make $2850 per month
Hello, I am CLARK , I make $2450 per month
Hello, I am JONES , I make $2975 per month
Hello, I am SCOTT , I make $3000 per month
Hello, I am FORD , I make $3000 per month
Hello, I am SMITH , I make $800 per month
Hello, I am ALLEN , I make $1600 per month
Hello, I am WARD , I make $1250 per month
Hello, I am MARTIN , I make $1250 per month