20151212 OCP047 60-80d.d.
63.which create table statemenbt is vaild?
d.create table ord_details(
ord_no number(2),
item_no numnber(3),
ord_data data default sysdate not null
需要注意的几个点,一个字段有多个限制的时候需要用空格隔开而不是逗号，default后面要加默认的值
64.evalueate the following select statement and view the exhibit to examine its output
select constraint_name,constraint_type,search_condition,r_constraint_name,delete_rule,status from user_constarants where
table_n ame=ORDERS
which two statements are true about the output?
a.in the second column,indicates a check constraint
第二列是现实约束的类型，外键约束，检查约束，唯一性约束等等
b.the status column indicates whether the table is currently in user
status；列现实的是约束的状态(enable或disable)而不是当前正在使用,
c.the r_consteraint_name column gives the alternative name for the constarint
错，如果一个约束是外键约束，那么该约束的r_constraint_name列是显示了该外检关联的对应表对应列的约束
d.the column delete_rule decides the state of the related rows int the child table when the correspondin row is deleted from the parant table
delete_rule列决定了当删除父表的记录时，相关联的记录的状态(保留或者删除)
66.which two statements are true about regarding multiple-row subqueries?
a.they can containt group functions
yes
b.they always contain a subquery within a subquery
多行子查询包含的子查询不限数量
c.they use the < all operator to imply less than the maximum
小于all就意外这要小于最小的
d.the can useed to retrieve multiple rows from a single table only
多行子查询可以检索任意数量的表？
e.they should not be used with the not in operator in the main query if null
is likely to be a part of the result of the subquery
not in 一个包含null的值永远返回false
68.the following are the staeps for a correlated subquery ,listed in random order
2.the candiate row is fetched from the table specified in the outer query
外查询上取一行
4.rows are returned by the inner query.after being evaluated with the value from the candiate row
in the outer query
用外查询的候选行的值做评估后，内查询返回记录
1.the where clause of the outer query is evaluated
判断是够符合外查询的where条件
3.repead
70.which two statements are true about the grouping function ?
a.it is used to find the groups forming the subtotal in a row
b.it is used toi identify the null value in the aggregate functions
grouping函数是用来区分一个单独的null值和一个代表集合所有值的nulkl值
c.it is used to form the group sets involved in generating the totals and subtotals
这是rollup的用法
d.it can be used with rollup and cube operators specified in the group by clause
71.given below is a list of datetime data types and examples of values stored in them in a random order
identify the option that correctly matches the data types with the values
a.interval year to month
时间跨度，单位 年，月 时间戳，要求制定时区
'+2-00'
b.tiemstamp with local time zone
时间戳，使用系统时区，所以不能指定时区 时间跨度 单位 填，小时，分，秒
c.timestamp with time zone
时间戳，要求制定时区 时间戳 ，使用系统时区，所以不能制定时区
d.interval day to second '+06 03:30:16 .00000'
时间跨度，单位 天，小时，分，秒 时间跨度 ，单位 年月
80.evalueted the following alter table statement;
alter table orders set unused order_date;
whch statement is true
a.the describe command would display the order_date column
以后该列相当于被删除，永远都不会显示出来的
b.rollback can be used to get back the order_date column in the orders table
ddl操作，不能被回滚
c.the order_date column should be empty for the alter table command to execute sucdessfully
set used 就是逻辑意义上的删除，不需要该列是空的
d.after executing the alter table command,you can add a new column called ordwrr_date to
the orders table
set unused 逻辑删除之后系统认为没有该列了，可以以原来的列明来命名列