多项选择题
Which are DML statements? （）
A.COMMIT
B.MERGE
C.UPDATE
D.DELETE
E.CREATE
F.DROP...
相关考题
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单项选择题
In which case would you use a FULL OUTER JOIN?（）
A.Both tables have NULL values.
B.You want all unmatched data from one table.
C.You want all matched data from both tables.
D.You want all unmatched data from both tables.
E.One of the tables has more data than the other.
F.You want all matched and unmatched data from only one table. -
单项选择题
You need to change the definition of an existing table. The COMMERCIALS table needs its DESCRIPTION column changed to hold varying length characters up to 1000 bytes. The column can currently hold 500 bytes per value. The table contains 20000 rows. Which statement is valid?（）
A.ALTER TABLE commercials MODIFY (description CHAR2(1000));
B.ALTER TABLE commercials CHANGE (description CHAR2(1000));
C.ALTER TABLE commercials CHANGE (description VARCHAR2(1000));
D.ALTER TABLE commercials MODIFY (description VARCHAR2(1000));
E.You cannot increase the size of a column if the table has rows. -
单项选择题
You need to modify the STUDENTS table to add a primary key on the STUDENT_ID column. The table is currently empty. Which statement accomplishes this task?（）
A.ALTER TABLE students ADD PRIMARY KEY student_id;
B.ALTER TABLE students ADD CONSTRAINT PRIMARY KEY (student_id);
C.ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY student_id;
D.ALTER TABLE students ADD CONSTRAINT stud_id_pk PRIMARY KEY (student_id);
E.ALTER TABLE students MODIFY CONSTRAINT stud_id_pk PRIMARY KEY (student_id);
