问Oracle 11g："With Clause“非常慢EN最近学习Oracle，所以在Vm中配置一个win10的虚拟机来安装Oracle 1...
with as短语,也叫做子查询部分(subquery factoring),可以让你做很多事情,定义一个sql片断,该sql片断会被整个sql语句所用到。 有的时候,是为了让sql语句的可读性更高些,也有可能是在union all的不同部分,作为提供数据的部分。 特别对于union all比较有用。 因为union all的每个部分可能相同,但是如果每个部分都去执...
With语句可以在查询中做成一个临时表/View,用意是在接下来的SQL中重用,而不需再写一遍。 With Clause方法的优点: 增加了SQL的易读性,如果构造了多个子查询,结构会更清晰。 示例: withsoloempas(selectdistinctsalaryfromhy_emp)selectavg(salary)from(selectdense_rank()over(orderbysalary)asseq, dense_rank()ove...
To keep it simple, the following example only references the aggregations once, where the SQL "WITH clause" is normally used when an aggregation is referenced multiple times in a query. We can also use the SQL-99 "WITH clause" instead of temporary tables. The Oracle SQL "WITH clause" will...
1、with table as 相当于建个临时表(用于一个语句中某些中间结果放在临时表空间的SQL语句),Oracle 9i 新增WITH语法,可以将查询中的子查询命名,放到SELECT语句的最前面。 语法就是 with tempname as (select ...) select ... 例子: with t as (select * from emp where depno=10) select...
FUNCTION with_function(p_id IN NUMBER) RETURN NUMBER IS BEGIN RETURN p_id; END; SELECT with_function(id) FROM test WHERE rownum = 1 / WITH_FUNCTION(ID) --- 1 SQL> 有意思的是,当WITH子句中包含PL/SQL声明时,分号";"不再能用作SQL语句的终止符。如果我们使用它,SQL*Plus会等待更多命令文本...
FUNCTION with_function(p_id IN NUMBER) RETURN NUMBER IS BEGIN RETURN p_id; END; SELECT with_function(id) FROM test WHERE rownum = 1 / WITH_FUNCTION(ID) --- 1 SQL> 有意思的是,当WITH子句中包含PL/SQL声明时,分号";"不再能用作SQL语句的终止符。如果我们使用它,SQL*Plus会等待更多命令文本...
select xm,zjh,dz,row_number()over(partition by zjh order by xm) 记录号 from cs 去重重复数据: with cs1 as (select xm,zjh,dz,row_number()over(partition by zjh order by zjh) 记录号 from cs)select * from cs1 where 记录号=1
with a as (select * from test) select * from a; 其实就是把一大堆重复用到的SQL语句放在with as 里面,取一个别名,后面的查询就可以用它 这样对于大批量的SQL语句起到一个优化的作用,而且清楚明了 下面是搜索到的英文文档资料 About Oracle WITH clause ...
Oracle allows you to use theUSINGclause to implicitly test for equality (=) when joining tables. Here’s the syntax of theLEFT JOINwith theUSINGclause: SELECTcolumn_listFROMXLEFTJOINYUSING(id);Code language:SQL (Structured Query Language)(sql) ...