多项选择题
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 than 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 a REUSE clause when creating a sequence to restart the sequence once it generates the maximum value defined for the sequence.
单项选择题 The EMP table contains these columns: LAST_NAME VARCHAR2 (25) SALARY NUMBER (6,2) DEPARTMENT_ID NUMBER (6) You need to display the employees who have not been assigned to any department. You write the SELECT statement: SELECT LAST_NAME, SALARY, DEPARTMENT_ID FROM EMP WHERE DEPARTMENT_ID = NULL; What is true about this SQL statement ?（）
单项选择题 Click the Exhibit button to examine the structures of the EMPLOYEES, DEPARTMENTS, and TAX tables. For which situation would you use a nonequijoin query?（）
单项选择题 Examine the description of the CUSTOMERS table: CUSTOMER_ID NUMBER(4) NOT NULL CUSTOMER_NAME VARCHAR2(100) NOT NULL STREET_ADDRESS VARCHAR2(150) CITY_ADDRESS VARCHAR2(50) STATE_ADDRESS VARCHAR2(50) PROVINCE_ADDRESS VARCHAR2(50) COUNTRY_ADDRESS VARCHAR2(50) POSTAL_CODE VARCHAR2(12) CUSTOMER_PHONE VARCHAR2(20) The CUSTOMER_ID column is the primary key for the table. Which statement returns the city address and the number of customers in the cities Los Angeles or San Francisco?（）