If you need to use this logic in many tables you could place it in a PL/SQL function. Then call this function in your SQL: FromOracle Database 23ai, theautomatic SQL transpilercan extract SQL expressions in PL/SQL. These are then part of the SQL statement, so at runtime it's as-i...
In the following example, the optimizer calculates the degree of parallelism. The statement always runs in parallel. SELECT /*+ PARALLEL/ last_name FROM employees; In the following example, the optimizer calculates the degree of parallelism, but that degree may be 1, in which case the statement...
The Oracle/PLSQL CASE statement has the functionality of an IF-THEN-ELSE statement. Starting in Oracle 9i, you can use the CASE statement within a SQL statement. Syntax The syntax for the CASE statement in Oracle/PLSQL is: CASE [ expression ] WHEN condition_1 THEN result_1 WHEN condition...
' || CURRENT_VALUE; END IF; ELSE CONDITIONS := CONDITIONS || ' = ' || ALIAS || '.' || CURRENT_VALUE || ' '; END IF; --循环值减1 SIGNS := SIGNS - 1; END LOOP; --拼接关联SQL TARGET_RESULTS := TARGET_RESULTS || 'LEFT JOIN (SELECT DISTINCT ' || QUERY_ITEMS || ',' ...
软解析:若SQL执行过,则从库高速缓存中取出解析的信息,直接使用。 硬解析:若SQL没有执行过,则做完全的SQL解析过程,生成执行计划,并放在缓存中以便重用。 软解析比硬解析快得多。 4、完全相同的语句 (1)视图v$sql可以查询存放在库高速缓存中的语句。
21-12-2022 10:37:44 CST Error executing statement: java.sql.SQLRecoverableException: Io exception: Connection reset java.sql.SQLRecoverableException: Io exception: Connection reset at oracle.jdbc.driver.SQLStateMapping.newSQLException(SQLStateMapping.java:101) at oracle.jdbc.driver.DatabaseError.new...
TDSQL PG版实现方法是将不再target_el以及columnref中的列作为group by列,通过pivot_expr_list对target_el中的聚集函数参数用case when进行重写,规则是“有值取值、没值取空”。 UNPivot可以将列属性转行数据, 本质是转化为 join lateral。实现方法是获取IN中的列,拼接成VALUES(…),将UNPIVOT column和FOR column...
InboundOperationType指定是要执行轮询还是通知入站操作。 默认值为轮询。 PolledDataAvailableStatement指定适配器执行的 SQL 语句,以确定是否有任何数据可用于轮询。 仅当记录可用时,才会执行为PollingStatement绑定属性指定的 SELECT 语句。 默认值为SELECT 1 FROM DUAL,这意味着无论要轮询的表是...
This tutorial explains how to create a parameterized view using SQL Macros. The examples use the built-in sales history schema so there are no setup steps. Script Simple Explain Plan This script explains the plan for a query of the sh.sales and sh.products tables. Both statements must be ...
(+)这种形式时Oracle数据库独有的,所以left join或right join 也需要了解。 层次查询(树型结构查询) 层次化查询,即树型结构查询,是SQL中经常用到的功能之一,通常由根节点,父节点,子节点,叶节点组成,其语法如下: SELECT [LEVEL] ,column,expression,... FROM table_name [WHERE where_clause] [[START WITH ...