之前上一家公司數據庫用的是informix數據庫,新公司數據庫用的是Oracle數據庫,所以還是需要重新學習一下,並做個筆記。
sql查詢語句基本語法:
1、別名的使用,別名使用As連接或者省略不寫。
SQL> SELECT EMPNO AS "Employee Number",
2 ename name,(500+sal)*12 "Annual Salary"
3 from emp;
結果:
Employee Number NAME Annual Salary
--------------- ---------- -------------
7369 SMITH 15600
7499 ALLEN 25200
7521 WARD 21000
7566 JONES 41700
7654 MARTIN 21000
7698 BLAKE 40200
7782 CLARK 35400
7788 SCOTT 42000
7839 KING 66000
7844 TURNER 24000
7876 ADAMS 19200
注意:當別名沒有被雙引號括起來時,別名的顯示結果爲大寫;如果別名中包含了特殊字符,或者想讓別名原樣顯示,就要使用雙引號把別名括起來。
2、字符串連接運算符 ||
SQL> SELECT ename ||' annual salary is '||(500+sal)*12 "Employee's Salary"
2 FROM emp;
結果:
Employee's Salary
--------------------------------------------------------------------
SMITH annual salary is 15600
ALLEN annual salary is 25200
WARD annual salary is 21000
JONES annual salary is 41700
MARTIN annual salary is 21000
BLAKE annual salary is 40200
CLARK annual salary is 35400
3、在sql語句中使用算數表達式+,-,*,/
SQL> SELECT empno,ename,(500+sal)*12
2 FROM EMP;
結果:
EMPNO ENAME (500+SAL)*12
---------- -------- ------------
7369 SMITH 15600
7499 ALLEN 25200
7521 WARD 21000
7566 JONES 41700
7654 MARTIN 21000
7698 BLAKE 40200
7782 CLARK 35400
7788 SCOTT 42000
7839 KING 66000
7844 TURNER 24000
7876 ADAMS 19200
4、使用DISTINCT查詢是去掉重複的行
SQL> SELECT DISTINCT deptno
2 FROM emp;
結果:
DEPTNO
----------
30
20
10
注意:DISTINCT可用於多列,此時的顯示結果爲每一種列組合只顯示一行。如:
SQL> SELECT DISTINCT deptno,job
2 FROM EMP;
結果:
DEPTNO JOB
---------- ---------
20 CLERK
30 SALESMAN
20 MANAGER
30 CLERK
10 PRESIDENT
30 MANAGER
10 CLERK
10 MANAGER
20 ANALYST
5、查詢是使用where限制性條件。
SQL> SELECT empno,ename,sal
2 FROM emp
3 WHERE SAL>=1500;
結果:
EMPNO ENAME SAL
---------- -------- ----------
7499 ALLEN 1600
7566 JONES 2975
7698 BLAKE 2850
7782 CLARK 2450
7788 SCOTT 3000
7839 KING 5000
7844 TURNER 1500
7902 FORD 3000
備註:6個常用的比較運算符
>(大於),<(小於),=(等於),<=(小於等於),>=(大於等於),!=或<>(不等於)
6、使用between 下限 and 上限,判斷數字型數據、字符串或者日期型數據在下限和上限之間,包含下限和上限。字符串和日期型數據需要用單引號括起來。
SQL> SELECT empno,ename,sal
2 FROM emp
3 WHERE sal BETWEEN 1500 AND 2900;
EMPNO ENAME SAL
---------- -------- ----------
7499 ALLEN 1600
7698 BLAKE 2850
7782 CLARK 2450
7844 TURNER 1500
SQL> SELECT empno,ename,sal,hiredate
2 FROM emp
3 WHERE hiredate BETWEEN '01-JAN-81' AND '31-MAY-82';
EMPNO ENAME SAL HIREDATE
---------- -------- ---------- ---------------
7499 ALLEN 1600 20-FEB-81
7521 WARD 1250 22-FEB-81
7566 JONES 2975 02-APR-81
7654 MARTIN 1250 28-SEP-81
7698 BLAKE 2850 01-MAY-81
7782 CLARK 2450 09-JUN-81
7839 KING 5000 17-NOV-81
7844 TURNER 1500 08-SEP-81
7900 JAMES 950 03-DEC-81
7902 FORD 3000 03-DEC-81
7934 MILLER 1300 23-JAN-82
備註:可以在 用not betbeen ... and ...之間,用來判斷數字型數據、字符串或者日期型數據沒有在下限和上限之間。
7、like模糊匹配,兩個通配符%,_
%:“%”代表零個或者多個字符
_:"_"代表一個且只能是一個字符
SQL> SELECT empno,ename,sal,job
2 FROM emp
3 WHERE job LIKE 'S_L_S%';
EMPNO ENAME SAL JOB
---------- ---------- ---------- ---------
7499 ALLEN 1600 SALESMAN
7521 WARD 1250 SALESMAN
7654 MARTIN 1250 SALESMAN
7844 TURNER 1500 SALESMAN
SQL> SELECT empno,ename,sal,hiredate
2 FROM emp
3 WHERE hiredate LIKE '%81';
EMPNO ENAME SAL HIREDATE
---------- ---------- ---------- ------------
7499 ALLEN 1600 20-FEB-81
7521 WARD 1250 22-FEB-81
7566 JONES 2975 02-APR-81
7654 MARTIN 1250 28-SEP-81
7698 BLAKE 2850 01-MAY-81
7782 CLARK 2450 09-JUN-81
7839 KING 5000 17-NOV-81
7844 TURNER 1500 08-SEP-81
7900 JAMES 950 03-DEC-81
7902 FORD 3000 03-DEC-81
8、使用轉義字符
先新建一個臨時表
SQL> CREATE table dept_temp
2 AS
3 SELECT *
4 FROM dept;
插入一條數據:
SQL> INSERT INTO ddept_temp
2 VALUES(88,'IT_RESEARCH','BEIJING');
轉移查詢:
SQL> SELECT *
2 FROM dept_temp
3 WHERE dname LIKE 'IT\_%' escape '\';
DEPTNO DNAME LOC
---------- -------------- -------------
88 IT_RESEARCH BEIJING
備註:定義'\'爲轉義符,即'_'字符不是通配符,而是它本來的含義。可以定義其它字符爲轉義字符。
SQL> SELECT *
2 FROM dept_temp
3 WHERE dname LIKE 'IT~_%' escape '~';
DEPTNO DNAME LOC
---------- -------------- -------------
88 IT_RESEARCH BEIJING