1. 准备数据
1.1. 查询数据
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INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4002,'photoshop设计基础','大众出版社',TO_DATE('2005-2-1','yyyy-mm-dd'),46.50,'刘晓静','1',9707,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4003,'photoshop设计基础','大众出版社',TO_DATE('2005-2-1','yyyy-mm-dd'),46.50,'刘晓静','1',9707,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4004,'photoshop设计基础','大众出版社',TO_DATE('2005-2-1','yyyy-mm-dd'),46.50,'刘晓静','0',null,null) INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4005,'数字图形处理','科学出版社',TO_DATE('2002-8-1','yyyy-mm-dd'),56.40,'王刚,赵明','1',9702,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4006,'数字图形处理','科学出版社',TO_DATE('2002-8-1','yyyy-mm-dd'),56.40,'王刚,赵明','0',null,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4007,'多媒体基础','科学出版社',TO_DATE('2006-1-1','yyyy-mm-dd'),43.70,'赵明','1',9702,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4008,'VC网络基础','青年出版社',TO_DATE('2004-3-1','yyyy-mm-dd'),28.00,'孙朋','0',null,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4009,'VC网络基础','青年出版社',TO_DATE('2004-3-1','yyyy-mm-dd'),28.00,'孙朋','1',9703,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4010,'数据库设计','大众出版社',TO_DATE('2007-9-1','yyyy-mm-dd'),76.00,'王六','1',9705,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4011,'通讯原理','科学出版社',TO_DATE('2001-6-1','yyyy-mm-dd'),45.50,'佟健刚','1',9704,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4012,'VC数据库程开发基础','科学出版社',TO_DATE('2006-4-1','yyyy-mm-dd'),54.00,'刘明,孙朋','0',null,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4013,'VC数据库程开发基础','科学出版社',TO_DATE('2006-4-1','yyyy-mm-dd'),54.00,'刘明,孙朋','1',9701,null); INSERT INTO BOOKINFO(BOOKID,BOOKNAME,PUBLISH,PUBDATE,PRICE,AUTHOR,STORE,READER,REMARKS) VALUES(4014,'数据库原理','科学出版社',TO_DATE('2005-1-1','yyyy-mm-dd'),38.50,'高义','0',null,null); |
1.2. 查询语句基础
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语法: SELECT [DISTINCT] Select_list FROM table_name [where_clause] [group_by_clause] [having condition] [order_by_clause] |
1.2.1. 查询关键字的顺序及功能
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顺序序号 |
子句关键字 |
子句功能 |
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1 |
SELECT |
从指定表中取出指定列的数据 |
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2 |
FROM |
指定要查询要操作的表 |
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3 |
WHERE |
用来规定一种选择查询的标准 |
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4 |
GROUP BY |
对结果集进行分组，通常与聚合函数一起使用 |
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5 |
HAVING |
返回选取的结果集中行的数目 |
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6 |
ORDER BY |
指定分组的搜寻条件 |
1.3. 查询表中列的数据
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SELECT * FROM BOOKINFO; SELECT BOOKID,BOOKNAME,PUBLISH,PUBDATE FROM BOOKINFO; --指定别名 SELECT BOOKID AS B_ID,BOOKNAME B_NAME,PUBLISH,PUBDATE FROM BOOKINFO; |
1.4. 去除查询结果中的重复记录
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语法： SELECT DISTINCT select_list FROM table_name; SELECT DISTINCT(BOOKNAME),PUBLISH,PUBDATE FROM BOOKINFO; |
1.4.1. distinct对NULL值得处理
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如果表中有多个null的数据，服务器会把这些数据视为相等 SELECT DISTINCT(READER)FROM BOOKINFO; |
1.5. 返回查询的部分数据(ROWNUM)
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查询BOOKINFO表中前2行记录 SELECT BOOKNAME,PUBLISH,READER FROM BOOKINFO WHERE ROWNUM <3; |
1.6. 单一条件查询
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语法： SELECT 列名1,列名2…… FROM 表名 WHERE 条件; SELECT BOOKNAME,PUBLISH FROM BOOKINFO WHERE PUBLISH='科学出版社'; |
1.6.1. 查询中使用比较表达式
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比较表达式 |
作用 |
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=（等于） |
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<（小于） |
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>（大于） |
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<>(不小于) |
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<=(小于等于) |
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>=(大于等于) |
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!=(不等于) |
1.6.2. 比较运算符
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SELECT BOOKNAME,PUBLISH,PRICE FROM BOOKINFO WHERE PRICE>50; |
1.6.3. 使用比较运算符比较字符
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SELECT BOOKNAME,PUBLISH,AUTHOR FROM BOOKINFO WHERE BOOKNAME<='多媒体基础'; |
1.7. 使用简单逻辑表达式
1.7.1. AND运算符
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AND运算符表示逻辑“与”的关系；当使用AND运算符组合两个逻辑表达式时，只有两个表达式均为TRUE时才返回TRUE; SELECT BOOKNAME,PUBLISH,PUBDATE,STORE FROM BOOKINFO WHERE PUBLISH='科学出版社' AND STORE='1'; |
1.7.2. OR运算符
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OR运算符实现逻辑“或”的运算关系，当使用OR运算符组合两个逻辑表达时，只要其中一个表达式的条件TRUE，结果便返回TRUE; SELECT BOOKNAME,PUBLISH,PRICE FROM BOOKINFO WHERE PUBLISH='科学出版社' OR PRICE>50; |
1.7.3. NOT运算符
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NOT运算符实现逻辑“非”的运算关系，用于对搜集条件的逻辑求反； SELECT BOOKNAME,PUBLISH FROM BOOKINFO WHERE NOT PUBLISH='大众出版社'; 上面操作相当于下面操作: FROM BOOKINFO WHERE PUBLISH!='大众出版社'; |
1.7.3.1. NOT运算符对NULL值得处理
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--要求在BOOKINFO表中查询编号不大于9704(包含没有读者)的所有图书记录； --没有查出READER为NULL的数据，如果READER为NULL，READER>9704这个条件不成立； SELECT BOOKNAME,PUBLISH,AUTHOR,STORE,READER FROM BOOKINFO WHERE NOT READER>9704; --相当于 SELECT BOOKNAME,PUBLISH,AUTHOR,STORE,READER FROM BOOKINFO WHERE READER<=9704; |
1.7.4. AND,OR,NOT的组合使用
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当AND和OR同时出现时，出现下面的运算关系:NOT优先级最高，而后是AND，最后是OR Condition1 OR Condition2 AND Condition3 Condition1 OR (Condition2 AND Condition3) SELECT BOOKNAME,PUBLISH,AUTHOR,PRICE,STORE,READER FROM BOOKINFO WHERE PUBLISH='青年出版社' OR PUBLISH='科学出版社' AND NOT PRICE>50; --相当于 SELECT BOOKNAME,PUBLISH,AUTHOR,PRICE,STORE,READER FROM BOOKINFO WHERE (PUBLISH='青年出版社' OR PUBLISH='科学出版社') AND NOT PRICE>50; |
1.8. 有关NULL值的判断
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语法: 判断一个值是否为NULL，采用IS [NOT] NULL判别式； SELECT BOOKNAME,PUBLISH,PRICE,READER FROM BOOKINFO WHERE READER IS NOT NULL; |
1.9.有关模糊查询
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语法: 表达式 [NOT] LIKE 条件 LIKE子句结合通配符使用： “_”可以替代一个字符； “%”可以代替个数不确定的字符； |
1.9.1. “_”通配符
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SELECT BOOKNAME,PUBLISH,PRICE,READER FROM BOOKINFO WHERE BOOKNAME LIKE '通__理'; |
1.9.2. “%”通配符
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“%”表示任意字符的匹配，且不计字符的多少； SELECT BOOKNAME,PUBLISH,PRICE,READER FROM BOOKINFO WHERE PUBLISH LIKE '科学%'; |
1.10. 指定范围查询
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语法： 表达式 [NOT] BETWEEN 表达式1 AND 表达式2 SELECT BOOKNAME,PUBLISH,PRICE,READER FROM BOOKINFO WHERE PRICE BETWEEN 35 AND 50; --相当于 SELECT BOOKNAME,PUBLISH,PRICE,READER FROM BOOKINFO WHERE PRICE >=35 AND PRICE<=50; --日期 SELECT BOOKNAME,PUBLISH,PRICE,READER,PUBDATE FROM BOOKINFO WHERE PUBDATE BETWEEN TO_DATE('2004-9-1','yyyy-mm-dd') AND TO_DATE('2007-9-1','yyyy-mm-dd'); |
1.11. 如何限制检索数据范围
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语法: 表达式 [NOT] IN (表达式1,表达式2… …); SELECT BOOKNAME,PUBLISH,PRICE,READER,PUBDATE FROM BOOKINFO WHERE READER IN(9702,9705,9701); --相当于 SELECT BOOKNAME,PUBLISH,PRICE,READER,PUBDATE FROM BOOKINFO WHERE READER=9702 OR READER=9701 OR READER=9705; |
1.12. 排序查询结果
1.12.1.基本排序
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ORDER BY子句子句一定要放在所有子句的最后； 升序排序：ASC 降序排序：DESC SELECT BOOKNAME,PUBLISH,PRICE,READER,PUBDATE FROM BOOKINFO WHERE READER IS NOT NULL ORDER BY READER; --使用NULLS LAST关键字将NULL值放到最后 SELECT BOOKNAME,PUBLISH,PRICE,READER,PUBDATE FROM BOOKINFO ORDER BY READER NULLS LAST; |
1.12.2. 多列排序
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使用ORDER BY子句可以根据两列或多列的结果进行排序，只需要用逗号分隔不同的关键词即可； SELECT BOOKNAME,PUBLISH,PRICE,READER,PUBDATE FROM BOOKINFO ORDER BY READER,PRICE ASC; |