Oracle PL/SQL之WITH查询 [转自] http://blog.csdn.net/t0nsha/article/details/6730855 为什么要用WITH? 1. 如果需要在一段复杂查询里多次应用同一个查询,用WITH可实现代码重用; 2. WITH查询类似将查询结果保留到用户临时表里,在大的复杂查询中可以减少IO,有一定的性能优化作用。 WITH查询有何限制与特性? 1...
该查询块的检索结果会被oracle 保存在用户的临时表空间中,该命名块就像虚表或者内联视图一样。 语法 代码语言:javascript 代码运行次数:0 运行 AI代码解释 WITH subquery_name AS (the aggregation SQL statement) SELECT (query naming subquery_name); With查询语句不是以select开始的,而是以“WITH”关键字开头。
[WITH [RECURSIVE] with_query [,…] ] SELECT … 其中,with_query的语法为: with_query_name [ ( column_name [, ...] ) ] AS ( {select| values | insert | update | delete} ) 关键要点如下: 每个CTE的AS语句指定的SQL语句,必须是可以返回查询结果的语句,可以是普通的SELECT语句,也可以是INSERT...
Bind variables enable you to run your query multiple times and pass in different values.Perform the following steps: 1 . Highlight the SQL statement in the HR_ORCL SQL Worksheet that you executed, right-click and select Create Report......
Oracle EXISTS Introduction to Oracle EXISTS EXISTS is a type of condition in Oracle database which can be defined as a condition or operator that is used with a sub query ( inner query or nested query is a query within another SQL query ) and upon execution of the sub query, if the ...
SQL (Structured Query Language,结构化查询语言) 是一种标准化的声明式编程语言,用于管理关系数据库并对其中的数据执行各种操作。SQL 最初创建于 1970 年代,逐渐成为关系数据库的标准编程语言。SQL 命令分为几种不同的类型,包括: 1. 数据定义语言 ( DDL )。也称为数据定义命令,因为它们用于定义数据表。
The Oracle PL/SQL language was designed to be a portable, high-performance transaction processing language that is tightly integrated with the SQL database query language. It is rare, indeed, to find a PL/SQL program that does not either read from or make changes to tables in a database....
PL/SQL is one of the core technologies at Oracle and is essential to leveraging the full potential of Oracle Database. PL/SQL combines the relational data access capabilities of the Structured Query Language with a flexible embedded procedural language, and it executes complex queries and programmat...
Operator and Function: The operators and functions for composing SQL expressions. For more contents about operators and functions, please refer to Instructions about how to construct a SQL query function.Get Values: All values in a field without duplicates. You can click the Get Unique Values ...
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