● not exists 关键字的用法 not exists (sql 不返回结果集为真) 示例图: 以上操作完整源码: --查询出有员工的部门有哪些 --in关键字尽量要少使用,因为性能比较低,可以使用 exists 来代替性能很高 select*fromdept twheret.deptnoin(selectdistinctdeptnofromemp
比如说,使用select 1 from table的结果是临时得到1列(列的值为1),其行数为表的记录数(行数),如果配合exists 语句则可以快速查询结果是否存在,而结果的具体数据不涉及到。 就像我上述提供的例子,它只查询验证dept表的字段deptno和emp的字段deptno是否有相等的情况,并且loc=‘NEW YORK’,而不需要知道dept表和emp...
NOT EXISTS (subquery);Code language:SQL (Structured Query Language)(sql) TheNOT EXISTSoperator returns true if the subquery returns no row. Otherwise, it returns false. Note that theNOT EXISTSoperator returns false if the subquery returns any rows with NULL. Oracle NOT EXISTS examples# See the...
发现和上面的not exist差不多!你是不是又恢复对not in的信心了呢? 但是 deletefromtb_scwhere(studentid,courseid,score)notin(selectstudentid,courseid,max(score)asscorefromtb_scgroupbystudentid,courseid) 确实是慢得让人发指,而将delete换成select之后,却并不慢,不信大家请执行下面sql: selecta.*fromtb...
AND NOT exists (SELECT 1FROM EIMS_WF_REL WF--where MVIEW.WFID = WF.Wfid)这个条件值:只要EIMS_WF_REL WF表里有一条数据,这个条件就不会成立.下面这样改造试试:SELECT COUNT(DISTINCT MVIEW.WFID)FROM EIMS_GWQUERY_FW MVIEW, EIMS_WF_AUTH AUTH, EIMS_WF_ACTIONTIME ATIM--追加代码,...
使用exists 不受null 的影响。 二.问题分析 我们在emp 表里查询的记录有空值,并且我们进行not in 和exists 操作时,都是用null 来判断的,如果我们换成非null 字段就可以正常进行操作了。 SQL> selectempno,ename from emp where empno not in (select empno from emp1); ...
This entry was posted inOracle,SQLNOT EXISTS,NOT INNULLsubquery first,secondandthird). When I was preparing a talk about optimizer statistics for data engineers recently, I took a closer look at it again. Oracle has now continuously improved the feature over several versions and has lifted many...
EXPORT_INVALID If the above configuration directive is not enough to validate your PL/SQL code enable this configuration directive to allow export of all PL/SQL code even if it is marked as invalid. The 'VALID' or 'INVALID' status applies to functions, procedures, packages, triggers and ...
在dm.ini 文件中修改 COMPATIBLE_MODE 参数的值。 + 利用 SQL 语句修改 COMPATIBLE_MODE 参数的值。SP_SET_PARA_VALUE(2,'COMPATIBLE_MODE',2); 或 ALTER SYSTEM SET 'COMPATIBLE_MODE'=2 SPFILE; 该参数为静态参数,需要重启数据库后生效。只选择迁移表,多出其他对象 如下图所示:...
Update HTML assessment reports to use modern editor to display SQL text SSMA v8.16 The v8.16 release of SSMA for Oracle contains the following changes: Add support for identity columns Remove support for legacy parser Fix issue with objects not refreshing from database ...