The subquery finds all the category_id values where COUNT is 1. We don’t need to have COUNT in the SELECT part of the subquery, however, if we do, the query will display an error. The UPDATE statement will update the price where the category meets the criteria of the subquery. Our ...
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(query naming subquery_name); Retuning to our oversimplified example, let’s replace the temporary tables with the SQL “WITH” clause”:
7)SQL> insert into a values(6,(select dname from dept where deptno=10)); //values里的某列使用了subquery引用另一个表的数据。 注意: 1)insert语句会有约束的问题,不符合约束条件的insert不能成功。 2)default不但可以用于insert语句, 也可以用于update语句(考点) 3)values后面不可以跟多列子查询。 SQL...
4:直接PLSQL 使用重建表(不推荐) 注意:重建表功能相当于 清掉所有数据 ,触发器,外键都会被清空,速度会很慢 ,效率并不是很好。 发布者:全栈程序员栈长,转载请注明出处:https://javaforall.cn/145625.html原文链接:https://javaforall.cn
Introduction to the Oracle subquery# A subquery is aSELECTstatement nested inside another statement such asSELECT,INSERT,UPDATE, orDELETE. Typically, you can use a subquery anywhere that you use an expression. Consider this following subquery example that uses theproductstable from thesample database...
1. With语句的语法 Oracle在9i中引入了with语句。with语句用来给查询语句中的子查询命名,随后就可以在查询语句的其他地方引用这个名称。语句格式如下: 1 WITH <alias_name> AS (subquery_sql_statement) 2 SELECT <column_name_list> FROM <alias>;
如果不加WITH CHECK OPTION则在插入时不会检查。 这里注意,subquery其实是不会实际执行的。 4.5多表插入语句 oracle从9i开始可以用一条insert语句实现向多个表中插入数据 Oracle Insert all有三种情况: 一、无条件 INSERT ALL 二、条件 INSERT ALL 三、条件 INSERT FIRST ...
方法1: 新建分区表, 然后insert select; 或者在创建新分区表的同时插入(CTAS,create table as select). 完成后做两次rename table操作. 方法2: 在线重定义, 使用DBMS_REDEFINITION, 步骤有点复杂 ,网上有很多介绍该方法的文章, 可以百度一下. 方法3: ...
当查询中多次用到某一部分时,可以用Oracle with语句创建一个公共临时表。因为子查询在内存临时表中,避免了重复解析,所以执行效率会提高不少。临时表在一次查询结束自动清除。 一般语法格式: 复制 withalias_name1 as (subquery1),alias_name2 as (subQuery2),……alias_nameN as (subQueryN)select col1,col2…...