ORACLE_SQL语句优化技术分析.pdf

在大多数情况下，Oracle 使用索引来更快地遍历表，而优化器主要根据定义的索引来提高性能。但是如果SQL语句的where子句中写的SQL代码不合理，会导致优化器删除索引，使用全表扫描。一般这种SQL语句就是所谓的劣质SQL语句。在编写 SQL 语句时，我们应该清楚优化器删除索引的原则，这有助于编写高性能的 SQL 语句。

(In most cases, Oracle uses indexes to traverse tables faster, while the optimizer mainly improves performance based on defined indexes. However, if the SQL code written in the where clause of the SQL statement is unreasonable, the optimizer will delete the index and use the full table scan. Generally, this kind of SQL statement is called inferior SQL statement. When writing SQL statements, we should be clear about the optimizer's principle of deleting indexes, which helps to write high-performance SQL statements.)

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