Oracle 基本数据查询

SELECT * FROM customers;

SELECT * FROM customers WHERE customer_id = 2;

SELECT ROWID,customer_id FROM customers;

SELECT rownum, customer_id, first_name||' '||last_name FULL_NAME
FROM customers;

SELECT SYSDATE FROM DUAL;

SELECT SYSDATE+2 FROM DUAL;

SELECT TO_DATE(SYSDATE) - TO_DATE('2-JAN-2011') FROM DUAL;

SELECT price*2 "Double Price"
FROM products;

SELECT * FROM customers
WHERE dob IS NULL;

--NVL的作用是将为空值的列加是默认值
SELECT CUSTOMER_ID, FIRST_NAME, LAST_NAME, NVL(DOB, '1-JAN-2000') AS DOB
FROM customers;

SELECT DISTINCT CUSTOMER_ID FROM purchases;

SELECT * FROM customers
WHERE customer_id <> 2;

SELECT * FROM customers
WHERE customer_id <= 3;

--比较操作符 >、 <、 >=、 <=、 <>或!=、 ANY、 SOME、 ALL
--只要大于ANY集合中的一个则满足条件
SELECT * FROM customers
WHERE customer_id > ANY(2,3,4);

--大于ALL中的所有数据才能为真
SELECT * FROM customers
WHERE customer_id > ALL(2,3,4);
--/*类似操作还有
--LIKE          NOT LIKE
--IN            NOT IN
--BETWEEN       NOT BETWEEN
--IS NULL       IS NOT NULL
--IS NAN        IS NOT NAN          NAN是非数字，NOT NAN是数字
--IS INFINITE   IS NOT INFINITE
--INFINITE是无穷的BINARY_FLOAT和BINARY_DOUBLE
--*/

SELECT * FROM customers
WHERE first_name NOT LIKE '_o%';

SELECT * FROM promotions
WHERE name LIKE '%\%%' ESCAPE '\';

SELECT * FROM customers
WHERE customer_id IN(2,3,4);

SELECT * FROM customers
WHERE customer_id NOT IN(2,3,4);

--此处注意在子查询中要考虑返回值为空的时候需要用NVL函数，
--否则NOT IN中只要有NULL值就会返回FALSE
SELECT * FROM customers
WHERE customer_id NOT IN(2,3,4,NULL);

SELECT * FROM customers
WHERE customer_id BETWEEN 1 AND 4;

SELECT * FROM customers
WHERE customer_id NOT BETWEEN 1 AND 4;

--NAN的意思是非数字
SELECT * FROM customers
WHERE customer_id IS NAN;

--逻辑运算符AND OR NOT
SELECT * FROM customers
WHERE dob>'01-JAN-1970' AND customer_id>3;

SELECT * FROM customers
WHERE dob>'01-JAN-1970' OR NOT customer_id > 3;

--ORDER BY进行排序
SELECT * FROM customers
ORDER BY last_name;

SELECT * FROM customers
ORDER BY first_name ASC, last_name DESC;

--直接用数字表示第几列
SELECT * FROM customers
ORDER BY 1 ASC, 2 DESC;

--多表连接查询
SELECT products.name, product_types.name
FROM products, product_types
WHERE products.product_type_id = product_types.product_type_id
AND products.product_id = 3;

SELECT products.name, product_types.name
FROM products, product_types
WHERE products.product_type_id = product_types.product_type_id
ORDER BY products.name;

--使用表别名
SELECT P.NAME, PT.NAME
FROM products P, product_types PT
WHERE p.product_type_id = pt.product_type_id
ORDER BY p.name;

--笛卡尔集
SELECT PT.product_type_id, P.product_id
FROM product_types PT, products P;

--多表连接查询
SELECT C.FIRST_NAME, C.LAST_NAME, P.NAME AS PRODUCT, PT.NAME AS TYPE
FROM customers C, purchases PR, products P, product_types PT
WHERE c.customer_id = pr.customer_id
AND p.product_id = pr.product_id
AND p.product_type_id = pt.product_type_id
ORDER BY p.name;

--不等连接
SELECT E.FIRST_NAME, E.LAST_NAME, E.TITLE, E.SALARY, SG.SALARY_GRADE_ID
FROM employees E, salary_grades SG
WHERE e.salary BETWEEN sg.low_salary AND sg.high_salary
ORDER BY sg.salary_grade_id;

--外连接('(+)'位于与含空值列相反的一边)
SELECT P.NAME PRODUCT, PT.NAME TYPE
FROM products P, product_types PT
WHERE p.product_type_id = pt.product_type_id (+)
ORDER BY p.name;

--左外连接和右外连接
--左外连接
SELECT P.NAME PRODUCT, PT.NAME TYPE
FROM products P, product_types PT
WHERE p.product_type_id = pt.product_type_id (+)
ORDER BY P.NAME;

--右外连接
SELECT P.NAME PRODUCT, PT.NAME TYPE
FROM products P, product_types PT
WHERE p.product_type_id (+) = pt.product_type_id
ORDER BY P.NAME;

--外连接的限制 1、只能在连接的一端使用外连接操作符，不能在两端都使用外连接操作符
--           2、不能同时会用一个外连接条件和另外一个使用OR操作符的连接条件

--自连接（同一个表进行连接， 必须会用不同的表别名来实现连接）
SELECT W.FIRST_NAME||' '||W.LAST_NAME||' WORKS FOR '
||M.FIRST_NAME||' '||M.LAST_NAME
FROM employees W, employees M
WHERE W.manager_id = M.employee_id
ORDER BY W.first_name;

SELECT W.FIRST_NAME||' '||W.LAST_NAME||' WORKS FOR '
||M.FIRST_NAME||' '||NVL(M.LAST_NAME, 'shareholders')
FROM employees W, employees M
WHERE W.manager_id = M.employee_id (+)
ORDER BY W.first_name;

--内连接
SELECT P.NAME, PT.NAME
FROM products P INNER JOIN product_types PT
ON p.product_type_id = pt.product_type_id（+）
ORDER BY p.name;

SELECT E.FIRST_NAME, E.LAST_NAME, E.SALARY, SG.SALARY_GRADE_ID
FROM employees E INNER JOIN salary_grades SG
ON e.salary BETWEEN sg.low_salary AND sg.high_salary
ORDER BY sg.salary_grade_id;

--使用USING关键字(使用USING关键字的时候最好不要使用表别名，否则会出错)
SELECT P.NAME, PT.NAME
FROM products P INNER JOIN product_types PT
USING(product_type_id)
ORDER BY p.name;

--多表内连接
SELECT C.LAST_NAME, P.NAME AS PRODUCT, PT.NAME AS TYPE
FROM customers C INNER JOIN purchases PR
USING (customer_id)
INNER JOIN products P
USING (product_id)
INNER JOIN product_types PT
USING (product_type_id)
ORDER BY p.name;

--多列内连接
--SELECT * FROM
--TABLE1 INNER JOIN TABLE2
--USING(COLUMN1,COLUMN2,…);

--使用USING关键字的外连接
--左外连接
SELECT P.NAME, PT.NAME
FROM products P LEFT OUTER JOIN product_types PT
USING(product_type_id);

--右外连接
SELECT P.NAME, PT.NAME
FROM products P RIGHT OUTER JOIN product_types PT
USING(product_type_id);

--全外连接
SELECT P.NAME, PT.NAME
FROM products P FULL OUTER JOIN product_types PT
USING(product_type_id);