■ A subquery in a DELETE, SELECT, or UPDATE statement ■ A query of a view or of a materialized view ■ A SELECT statement with the DISTINCT operator ■ A SELECT statement with a GROUP BY clause or ORDER BY clause ■ A SELECT statement that is combined with another SELECT statement wit...
Subquery Factoring, 其实就是平常比较熟悉的With语句,Adrian Billington 在他的网站上写了一篇介绍Subquery Factoring很好的文章,见这里。这篇Blog同样是对他的这篇文章的笔记。 With语句一般有两种用途,一种就是用来把复杂的SQL语句简单化:复杂的SQL语句一般都会嵌套很多层次,无论是写起来还是读起来都很困难,通过用Wit...
使用子查询创建表的语法: create table t_table [(column, column...)] as subquery; //如果只想创建表结构,不需要表中的数据,可以给一个永远为假的条件 create table t_table1 as select * from t_table2 where 1=2; 示例:创建person表: create table person( pid number(10), name varchar2(10)...
In this example, if the deptno column has a 10 in it, the SQL query will return the value accounting rather than the number 10. If the deptno is not 10, 20, 30, or 40, then the CASE statement will fall through to the ELSE clause, which will return unassigned. Note that with a s...
1.如果在RANKing中有多个分区，那么在每个分区中都会有排在第一位的行，并且CASE表达式期望从子查询中...
CASE WHEN COUNT(*) > 0 THEN 'Y' ELSE 'N' END FROM order_line o WHERE o.product_id = p.product_id ); The subquery will perform a COUNT function using a CASE statement to determine if the returned value is Y or N depending on the value of COUNT. It is calculated for each produc...
带有连接的Oracle SQL case语句产生奇怪的结果[duplicate]这是意料之中的，我会说，因为一个名字排除另...
The SQL used to gather index stats from any of the calls to dbms_stats.gather_xxx_stats() does a simple select statement that is hinted to access the index. In my case the indexes were all fairly small – smaller than the critical number of blocks that trigger sampling methods –so Ora...
subquery:It refers to the sub-query which is a SELECT statement and it is query within another query. How EXISTS work in Oracle? This function is used with a sub query to evaluate whether any row is returned by the sub-query. So when we execute the query the sub-query is executed fir...
The second plan shows us only one hash anti-join, and the predicate information tells us it’s referencing the occurence of emp with the alias e3. It looks as if the optimizer has “lost” the second subquery – but how could that happen? The biggest clue is in the Outline Data ...