基础部分：

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下面的练习题是针对订单表和订单详表：

Order_id, Customer_id, order_date
O1, C1, 01-Jan-2000
O2, C2, 01-Jan-2002
O3, C3, 01-Apr-2002
O4, C4, 01-Apr-2003
O5, C4, 01-Jan-2006
O6,C1, 01-May-2006

Item_id, Order_id

I1, O1

I2, O1

I3, O1

I1, O2

I5, O3

准备数据

CREATE TABLE ORDER_LIST (ORDER_ID CHAR(2), CUSTOMER_ID CHAR(2), ORDER_DATE DATE);
INSERT INTO ORDER_LIST VALUES (‘O1′,’C1’,TO_DATE(‘2000-01-01′,’YYYY-MM-DD’));
INSERT INTO ORDER_LIST VALUES (‘O2′,’C2’,TO_DATE(‘2002-01-01′,’YYYY-MM-DD’));
INSERT INTO ORDER_LIST VALUES (‘O3′,’C3’,TO_DATE(‘2002-04-01′,’YYYY-MM-DD’));
INSERT INTO ORDER_LIST VALUES (‘O4′,’C4’,TO_DATE(‘2003-04-01′,’YYYY-MM-DD’));
INSERT INTO ORDER_LIST VALUES (‘O5′,’C4’,TO_DATE(‘2006-01-01′,’YYYY-MM-DD’));
INSERT INTO ORDER_LIST VALUES (‘O6′,’C1’,TO_DATE(‘2006-04-01′,’YYYY-MM-DD’));
CREATE TABLE ORDER_ITEMS (ITEM_ID CHAR(2), ORDER_ID CHAR(2));
INSERT INTO ORDER_ITEMS VALUES (‘I1′,’O1’);
INSERT INTO ORDER_ITEMS VALUES (‘I2′,’O1’);
INSERT INTO ORDER_ITEMS VALUES (‘I3′,’O1’);
INSERT INTO ORDER_ITEMS VALUES (‘I1′,’O2’);
INSERT INTO ORDER_ITEMS VALUES (‘I5′,’O2’);
INSERT INTO ORDER_ITEMS VALUES (‘I1′,’O3’);
INSERT INTO ORDER_ITEMS VALUES (‘I4′,’O1’);
INSERT INTO ORDER_ITEMS VALUES (‘I1′,’O4’);

Given order and order items tables, select customer ids of customers who placed orders with more than 3 items (having or subquery)

SELECT A.CUSTOMER_ID, COUNT(B.ITEM_ID)
FROM ORDER_LIST A, ORDER_ITEMS B
WHERE A.ORDER_ID = B.ORDER_ID
GROUP BY A.CUSTOMER_ID
HAVING COUNT(B.ITEM_ID) > 3;

Give SQL for the list of customer_ids who placed more than 1 order

SELECT Customer, COUNT(OrderID) FROM Orders
GROUP BY Customer
HAVING Count(OrderID) > 1

Give the Sql for the list of customer_ids who have placed at least 1 order in 2000 and at least 1 order in 2006.

SELECT Customer, COUNT(OrderID) FROM Orders
GROUP BY Customer
HAVING ((Count(OrderID) > 1 AND TO_CHAR(order_date,'YYYY') = 2000) OR (Count(OrderID) > 1 AND TO_CHAR(order_date,'YYYY') = 2006))

Please write a sql which can generate the number of Orders for each year, 2000 to 2006.

SELECT A.YEAR,NVL(B.ORDER_NUMBER,0)
FROM (SELECT 2001 AS YEAR FROM DUAL
UNION
SELECT 2002 AS YEAR  FROM DUAL
UNION
SELECT 2003 AS YEAR  FROM DUAL
UNION
SELECT 2004 AS YEAR  FROM DUAL
UNION
SELECT 2005 AS YEAR  FROM DUAL
UNION
SELECT 2006 FROM DUAL) A, 
(SELECT TO_CHAR(ORDER_DATE,'YYYY') YEAR, COUNT(ORDER_ID) ORDER_NUMBER
FROM ORDER_LIST
GROUP BY TO_CHAR(ORDER_DATE,'YYYY')) B
WHERE A.YEAR = B.YEAR (+)
ORDER BY A.YEAR;

进阶部分：

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下面的练习题是针对员工表：

emp_id dep_id manager_id start_date salary
———————————–
1,1,null,2000-01-01,16000
2,1,1,2002-01-01,20000
3,1,1,2002-04-01,9000
4,1,1,2003-04-01,1000
5,2,null,2006-01-01,20000
6,2,5,2006-04-01,28000
7,2,5,2000-04-01,500

准备数据：

CREATE TABLE employee (emp_id NUMBER(5), dep_id NUMBER(5), manager_id NUMBER(5) ,start_date DATE, salary NUMBER(5));
INSERT INTO employee VALUES (1,1,null,TO_DATE(‘2000-01-01′,’YYYY-MM-DD’), 16000);
INSERT INTO employee VALUES (2,1,1,TO_DATE(‘2002-01-01′,’YYYY-MM-DD’), 20000);
INSERT INTO employee VALUES (3,1,1,TO_DATE(‘2002-04-01′,’YYYY-MM-DD’), 9000);
INSERT INTO employee VALUES (4,1,1,TO_DATE(‘2003-04-01′,’YYYY-MM-DD’), 1000);
INSERT INTO employee VALUES (5,2,null,TO_DATE(‘2006-01-01′,’YYYY-MM-DD’), 20000);
INSERT INTO employee VALUES (6,2,5,TO_DATE(‘2006-04-01′,’YYYY-MM-DD’), 28000);
INSERT INTO employee VALUES (7,2,5,TO_DATE(‘2000-04-01′,’YYYY-MM-DD’), 500);

Display the employee records who joins the department before their manager?

SELECT a.*
FROM employee a, employee b
WHERE a.manager_id = b.emp_id
AND a.start_date < b.start_date;

Display employee records getting more salary than the average salary in their department?

SELECT a.*
FROM employee a, (
SELECT dep_id, AVG(salary) avg_sal
FROM employee
GROUP BY dep_id) b
WHERE a.dep_id = b.dep_id
AND a.salary > b.avg_sal

或相关子查询的写法：

SELECT a.*
FROM employee a
WHERE salary > (SELECT AVG(salary) max_sal
FROM employee b
WHERE a.dep_id = b.dep_id);

Display the highest paid employee in each department.

SELECT a.*
FROM employee a, (
SELECT dep_id, MAX(salary) max_sal
FROM employee
GROUP BY dep_id) b
WHERE a.dep_id = b.dep_id 
AND a.salary = b.max_sal

或

SELECT a.*
FROM employee a
WHERE salary = (
SELECT MAX(salary) max_sal
FROM employee b
WHERE a.dep_id = b.dep_id );