Sales details are being stored on a daily basis in the SALES_2007 table. A large amount of data is added to the table daily. To save disk space，you issued the following command： ALTER TABLE sales_2007 COMPRESS FOR ALL OPERATIONS； What would be the outcome of this command？（） [" It produces an error because data already exists in the table."," It produces an error because compression can be enabled at table creation only."," It compresses all data added or modified henceforth but the existing data in the table is not compressed immediately."," It immediately compresses all existing data as well as new data， resulting from either fresh additions or modifications to existing data."]
砌筑砂浆中，水泥用量不应（）。 ["小于400kg\/m3","小于300kg\/m3","小于250kg\/m3","小于200kg\/m3"]
下列不属于方向控制回路是（）。 ["换向和闭锁回路","调压和卸载回路","节流调速和速度换接回路","顺序动作回路"]
零序电流一般，只有在系统（）才会出现。 ["相间故障时","接地故障或非全相运行时","振荡时"]
What should be done to add lines from a Purchase Request （PR） to a Requests for Quotation （RFQ）？ （） [" Hyperlink to the PR tab and add each line."," Go to the Vendors tab in the RFQ application and click Create PO."," Go to the Quotation tab in the RFQ application and select RFQ lines."," Select Action in the RFQ application and click Copy PR line item to RFQ."]
直接计数法计数比客观实际的数值要（）。
