题目内容

采用单体支柱的采煤工作面在放顶线附近,若出现大岩块且大岩块沿工作面推进方向的长度超过一次放顶步距时,在大岩块的范围内要()。

A. 缩短控顶距
B. 延长控顶距
C. 控顶距不变

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Evaluate this SQL statement: 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; In the statement, which capabilities of a SELECT statement are performed?()

A. Selection, projection, join
B. Difference, projection, join
C. Selection, intersection, join
D. Intersection, projection, join
E. Difference, projection, product

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