基本SQL SELECT语句
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目标
通过本章学习,您将可以:
• 列举 SQL SELECT语句的功能。
• 执行简单的选择语句。
• SQL 语言和 SQL*Plus 命令的不同。
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Copyright © Oracle Corporation, 2001. All rights reserved.
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SQL SELECT 语句的功能
列
表
表1
行
表
表2
Join
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Copyright © Oracle Corporation, 2001. All rights reserved.
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基本 SELECT 语句
SELECT
SELECT
FROM
FROM
*|{[DISTINCT] column|expression [alias],...}
*|{[DISTINCT] column|expression [alias],...}
table;
table;
• SELECT 标识 选择哪些列。
• FROM 标识从哪个表中选择。
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选择全部列
SELECT *
FROM departments;
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选择特定的列
SELECT department_id, location_id
FROM departments;
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Writing SQL Statements
• SQL 语言大小写不敏感。
• SQL 可以写在一行或者多行
• 关键字不能被缩写也不能分行
• 各子句一般要分行写。
• 使用缩进提高语句的可读性。
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列头设置
• SQL*Plus:
– 字符和日期类型的列左对齐
– 字符类型的列右对齐
– 默认头显示方式:大写
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Copyright © Oracle Corporation, 2001. All rights reserved.
鸿鹄论坛: bbs.hh010.com 鸿鹄书院: book.hh010.com