简述sequence，all，choice三个元素的作用和使用方法。
简述sequence，all，choice三个元素的作用和使用方法。
相关考题：
We all enjoy our freedom of choice and do not like to see it____when it is within the legal and moral boundaries of society. A.compactedB.restrictedC.despersedD.delated
以下对ASN.1的数据类型描述正确的是（）。A、每个数据类型（包括CHOICE和ANY）都有标签B、分别用SEQUENCE和SEQUENCE OF表示相同类型和不同类型元素的序列C、分别用SET和SET OF表示不同类型和相同类型元素的集合D、隐含标签的语义是在一个基本类型上加上新标签，从而导出一个新类型
The customer asks for a scalable SQL server solution. What advantages supports the choice of the System x3950？（）A、More processing ’head room’ for a SQL infrastructure using eXpand on DemandB、A more affordable platform choice than HP Itanium based serverC、IBM Services to install and support the solutionD、All of the above
What is true about sequences? （）A、Once created, a sequence belongs to a specific schema.B、Once created, a sequence is linked to a specific table.C、Once created, a sequence is automatically available to all users.D、Only the DBA can control which sequence is used by a certain table.E、Once created, a sequence is automatically used in all INSERT and UPDATE statements.
Which two statements about sequences are true? （）A、You use a NEXTVAL pseudo column to look at the next possible value that would be generated from a sequence, without actually retrieving the value.B、You use a CURRVAL pseudo column to look at the current value just generated from a sequence, without affecting the further values to be generated from the sequence.C、You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence.D、You use a CURRVAL pseudo column to generate a value from a sequence that would be used for a specified database column.E、If a sequence starting from a value 100 and incremented by 1 is used by more then one application, then all of these applications could have a value of 105 assigned to their column whose value is being generated by the sequence.F、You use REUSE clause when creating a sequence to restart the sequence once it generates the maximum value defined for the sequence.
单选题以下对ASN.1的数据类型描述正确的是（）。A每个数据类型（包括CHOICE和ANY）都有标签B分别用SEQUENCE和SEQUENCE OF表示相同类型和不同类型元素的序列C分别用SET和SET OF表示不同类型和相同类型元素的集合D隐含标签的语义是在一个基本类型上加上新标签，从而导出一个新类型
单选题What is true about sequences? （）AOnce created, a sequence belongs to a specific schema.BOnce created, a sequence is linked to a specific table.COnce created, a sequence is automatically available to all users.DOnly the DBA can control which sequence is used by a certain table.EOnce created, a sequence is automatically used in all INSERT and UPDATE statements.