目录
目录...........................................................................................................................................2
第 1 章 模块功能概要描述......................................................................................................4
第 2 章 SQL 语句编写注意问题.............................................................................................5
IS NULL 与 IS NOT NULL.......................................................................................5
联接列 ........................................................................................................................5
带通配符（%）的 like 语句.....................................................................................6
Order by 语句 .........................................................................................................6
NOT.....................................................................................6
IN 和 EXISTS .........................................................................7
第 3 章 SQL 语句性能优化 .....................................................................................................9
选用合适的 ORACLE 优化器 ..................................................................................9
访问 Table 的方式 .....................................................................................................9
共享 SQL 语句.........................................................................................................10
选择最有效率的表名顺序(只在基于规则的优化器中有效)................................11
WHERE 子句中的连接顺序 ...................................................................................12
SELECT 子句中避免使用 ‘ *’................................................................................13
减少访问数据库的次数 ..........................................................................................13
使用 DECODE 函数来减少处理时间....................................................................14
整合简单,无关联的数据库访问 .............................................................................15
删除重复记录 ........................................................................................................16
用 TRUNCATE 替代 DELETE.............................................................................16
尽量多使用 COMMIT...........................................................................................16
计算记录条数 ........................................................................................................17
用 Where 子句替换 HAVING 子句......................................................................17
减少对表的查询 ....................................................................................................17
通过内部函数提高 SQL 效率...............................................................................18
使用表的别名(Alias) .............................................................................................20
用 EXISTS 替代 IN................................................................................................20
用 NOT EXISTS 替代 NOT IN. ............................................................................21
用表连接替换 EXISTS..........................................................................................21
用 EXISTS 替换 DISTINCT..................................................................................22
识别’低效执行’的 SQL 语句...........................................................................22
使用 TKPROF 工具来查询 SQL 性能状态 .........................................................23
用 EXPLAIN PLAN 分析 SQL 语句....................................................................23
用索引提高效率 ....................................................................................................25
索引的操作 ............................................................................................................25
基础表的选择 ........................................................................................................27
