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FOR Loops RulesReference the counter only within the loop;it is undefined outside the loop.Do not reference the counter as the target of an assignment.Neither loop bound should be NULL.Use the REVERSE keyword to force the loop to decrement from the upper bound to the lower bound.You must still make 阅读全文
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Logic TablesBuild a simple Boolean condition with a comparision operator.ANDTRUEFALSENULLTRUETRUEFALSENULLFALSEFALSEFALSEFALSENULLNULLFALSENULL ORTRUEFALSENULLTRUETRUETRUETRUEFALSETRUEFALSENULLNULLTRUENULLNULLNOTTRUEFALSEFALSETRUENULLNULLBoolean Expression or Logincal ExpressionWhat is the valu... 阅读全文
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ObjectivesAfter completing this lesson,you should be able to do the following:Identify the uses and types of control structuresConstruct an IF statementUse CASE statements and CASE expressionsConstruct and identify loop statementsUse guidelines when using conditional control structuresPL/SQL中,要区分sta 阅读全文
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1、在一个pl/sql block中,可以有多个transaction,一个transaction可以跨越多个PL/SQL block;PL/SQL块执行完成,但是事务没有提交SQL> begin 2 insert into tt values(1); 3 end; 4 /PL/SQL procedure successfully completed.SQL> select * from tt; ID---------- 0 1验证事务没有提交方法SQL> select addr from v$transaction;ADDR-----... 阅读全文
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当磁盘大小超过标准时会有报警提示,这时如果掌握df和du命令是非常明智的选择。 df可以查看一级文件夹大小、使用比例、档案系统及其挂入点,但对文件却无能为力。 du可以查看文件及文件夹的大小。 两者配合使用,非常有效。比如用df查看哪个一级目录过大,然后用df查看文件夹或文件的大小,如此便可迅速确定症结。 下面分别简要介绍df命令可以显示目前所有文件系统的可用空间及使用情形,请看下列这个例子:View Code [oracle@arcerzhang DATACENTER]$ df -hFilesystem Size Used Avail Use% Mounted on/... 阅读全文