多项选择题
A.A subquery should retrieve only one row.
B.A subquery can retrieve zero or more rows.
C.A subquery can be used only in SQL query statements.
D.Subqueries CANNOT be nested by more than two levels.
E.A subquery CANNOT be used in an SQL query statement that uses group functions.
F.When a subquery is used with an inequality comparison operator in the outer SQL statement, the column list in the SELECT clause of the subquery should contain only one column.
单项选择题 Examine the structure of the EMPLOYEES and NEW_EMPLOYEES tables: EMPLOYEES EMPLOYEE_ID NUMBER Primary Key FIRST_NAME VARCHAR2(25) LAST_NAME VARCHAR2(25) HIRE_DATE DATE NEW_EMPLOYEES EMPLOYEE_ID NUMBER Primary Key NAME VARCHAR2(60) Which UPDATE statement is valid?（）
单项选择题 Which view should a user query to display the columns associated with the constraints on a table owned by the user?（）
多项选择题 Which four are attributes of single row functions? （）