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单选题
你要关闭SALES表中UNIT_PRICE列的非NULL约束。下列哪个语句能完成这个操作？（）
A
alter table sales modify（unit_prices null）
B
alter table sales modify（unit_prices not null）
C
alter table sales add（unit_prices null）
D
alter table sales add（unit_prices not null）
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你要关闭SALES表中UNIT_PRICE列的非NULL约束。下列哪个语句能完成这个操作？（）A、alter table sales modify（unit_prices null）B、alter table sales modify（unit_prices not null）C、alter table sales add（unit_prices null）D、alter table sales add（unit_prices not null）
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You are modifying a table named Product in a SQL Server 2005 database. You want to add a new column named FriendlyName to the Product table. A friendly name for each product will be stored in this column. The table currently contains data. The sales department has not yet created a friendly name for each product. FriendlyName is a required value for each product. You want to add this new column by using the least amount of effort. What should you do？（）A、Define the new column as NULL.Update the FriendlyName column to the same value as the productName column. Alter the FriendlyName column to be NOT NULL.B、Define the new column as NOT NULL with a default value of ’Undefined.’C、Define the new column as NULL. Use application logic to enforce the data constraint.D、Define the new column as NULL with a default value of ’Undefined.’
考题
单选题你要关闭SALES表中UNIT_PRICE列的非NULL约束。下列哪个语句能完成这个操作？（）A
alter table sales modify（unit_prices null）B
alter table sales modify（unit_prices not null）C
alter table sales add（unit_prices null）D
alter table sales add（unit_prices not null）
考题
单选题发出下列语句：alter table sales drop columm profit；何时从Oracle中实际删除列？（）A
执行语句后立即删除B
发出alter table drop unused columns命令之后C
发出alter table set unused columns命令之后D
发出alter table modify命令之后
考题
单选题如果希望更新表authors中的first_name列为非空，那么可以使用哪个语句？（）A
alter table authors add first_name not nullB
alter table authors modify first_name not nullC
alter table authors alter first_name not nullD
alter table authors drop first_name not null
考题
单选题The EMPLOYEES table has these columns:LAST_NAME VARCHAR2(35) SALARY NUMBER(8,2) HIRE_DATE DATEManagement wants to add a default value to the SALARY column. You plan to alter the table by using this SQL statement:ALTER TABLE EMPLOYEES MODIFY (SALARY DEFAULT 5000);Which is true about your ALTER statement?（）A
Column definitions cannot be altered to add DEFAULT values.B
A change to the DEFAULT value affects only subsequent insertions to the table.C
Column definitions cannot be altered to add DEFAULT values for columns with a NUMBER data type.D
All the rows that have a NULL value for the SALARY column will be updated with the value 5000.
考题
单选题You are modifying a table named Product in a SQL Server 2005 database. You want to add a new column named FriendlyName to the Product table. A friendly name for each product will be stored in this column. The table currently contains data. The sales department has not yet created a friendly name for each product. FriendlyName is a required value for each product. You want to add this new column by using the least amount of effort. What should you do？（）A
Define the new column as NULL.Update the FriendlyName column to the same value as the productName column. Alter the FriendlyName column to be NOT NULL.B
Define the new column as NOT NULL with a default value of ’Undefined.’C
Define the new column as NULL. Use application logic to enforce the data constraint.D
Define the new column as NULL with a default value of ’Undefined.’
考题
单选题You just issued the following statement: ALTER TABLE SALES DROP COLUMN PROFIT. Which of the following choices identifies when the column will actually be removed from Oracle?（）A
Immediately following statement execution B
After the ALTER TABLE DROP UNUSED COLUMNS command is issued C
After the ALTER TABLE SET UNUSED COLUMN command is issued D
After the ALTER TABLE MODIFY command is issued
考题
单选题Which statement adds a constraint that ensures the CUSTOMER_NAME column of the CUSTOMERS table holds a value?（）A
ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;B
ALTER TABLE customers MODIFY CONSTRAINT cust_name_nn CHECK customer_name IS NOT NULL;C
ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn NOT NULL;D
ALTER TABLE customers MODIFY customer_name CONSTRAINT cust_name_nn IS NOT NULL;E
ALTER TABLE customers MODIFY name CONSTRAINT cust_name_nn NOT NULL;F
ALTER TABLE customers ADD CONSTRAINT cust_name_nn CHECK customer_name NOT NULL;
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