In which of the following cases would you not use the USING clause?
Answer:
a. You want to use a NATURAL join, but you want to restrict the number of columns in the join condition.
b. The tables to be joined have columns with the same name and compatible data types.
c. You want to create a nonequijoin.
d. The tables to be joined have multiple NULL columns.The following query uses which operations of relational algebra?
SELECT e.EMPLOYEE_ID, e.LAST_NAME, e.DEPARTMENT_ID, d.DEPARTMENT_NAME FROM EMP e, DEPARTMENT d
WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID;
Answer:
a. Only Join
b. Projection, join
c. Selection, join
d. Selection, projection, join
Answer:
a. You want to use a NATURAL join, but you want to restrict the number of columns in the join condition.
b. The tables to be joined have columns with the same name and compatible data types.
c. You want to create a nonequijoin.
d. The tables to be joined have multiple NULL columns.The following query uses which operations of relational algebra?
SELECT e.EMPLOYEE_ID, e.LAST_NAME, e.DEPARTMENT_ID, d.DEPARTMENT_NAME FROM EMP e, DEPARTMENT d
WHERE e.DEPARTMENT_ID = d.DEPARTMENT_ID;
Answer:
a. Only Join
b. Projection, join
c. Selection, join
d. Selection, projection, join
解决方案 »
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