多项选择题

Which two statements are true about constraints? （）

A.The UNIQUE constraint does not permit a null value for the column.
B.A UNIQUE index gets created for columns with PRIMARY KEY and UNIQUE constraints.
C.The PRIMARY KEY and FOREIGN KEY constraints create a UNIQUE index.
D.The NOT NULL constraint ensures that null values are not permitted for the column.

相关考题

The EMPLOYEES table has these columns:LAST_NAME VARCHAR...

单项选择题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.

Examine the structure of the EMPLOYEES table: EMPLOYEE_...

单项选择题

Examine the structure of the EMPLOYEES table:
EMPLOYEE_ID NUMBER NOT NULL
EMP_NAME VARCHAR2(30)
JOB_ID VARCHAR2(20)
SAL NUMBER
MGR_ID NUMBER
DEPARTMENT_ID NUMBER
You want to create a SQL script file that contains an INSERT statement. When the script is run, the INSERT statement should insert a row with the specified values into the EMPLOYEES table. The INSERT statement should pass values to the table columns as specified below:
EMPLOYEE_ID: Next value from the sequence
EMP_ID_SEQ EMP_NAME and JOB_ID: As specified by the user during run time, through substitution variables
SAL: 2000
MGR_ID: No value
DEPARTMENT_ID: Supplied by the user during run time through substitution variable. The INSERT statement should fail if the user supplies a value other than 20 or 50.
Which INSERT statement meets the above requirements?（）

A.INSERT INTO employees VALUES (emp_id_seq.NEXTVAL, '&ename', '&jobid', 2000, NULL, &did);
B.INSERT INTO employees VALUES (emp_id_seq.NEXTVAL, '&ename', '&jobid', 2000, NULL, &did IN (20,50));
C.INSERT INTO (SELECT * FROM employees WHERE department_id IN (20,50)) VALUES (emp_id_seq.NEXTVAL, '&ename', '&jobid', 2000, NULL, &did);
D.INSERT INTO (SELECT * FROM employees WHERE department_id IN (20,50) WITH CHECK OPTION) VALUES (emp_id_seq.NEXTVAL, '&ename', '&jobid', 2000, NULL, &did);
E.INSERT INTO (SELECT * FROM employees WHERE (department_id = 20 AND department_id = 50) WITH CHECK OPTION ) VALUES (emp_id_seq.NEXTVAL, '&ename', '&jobid', 2000, NULL, &did);

Which SELECT statement should you use to extract the ye...

单项选择题Which SELECT statement should you use to extract the year from the system date and display it in the format "1998"?（）

A.SELECT TO_CHAR(SYSDATE,'yyyy') FROM dual;
B.SELECT TO_DATE(SYSDATE,'yyyy') FROM dual;
C.SELECT DECODE(SUBSTR(SYSDATE, 8), 'YYYY') FROM dual;
D.SELECT DECODE(SUBSTR(SYSDATE, 8), 'year') FROM dual;
E.SELECT TO_CHAR(SUBSTR(SYSDATE, 8,2),'yyyy') FROM dual;

1Z0-007

Which two statements are true about constraints? （）