Consider the query: Mysql＞ SET @run = 15; Mysql＞ EXPLAIN SELECT objective, stage, COUNT (stage) FROM iteminformation WHERE run=@run AND objective=’7.1’ GROUP BY objective,stage ORDER BY stage; The iteminformation table has the following indexes; Mysql＞ SHOW INDEXES FROM iteminformation: This query is run several times in an application with different values in the WHERE clause in a growing data set. What is the primary improvement that can be made for this scenario?（） Do not pass a user variable in the WHERE clause because it limits the ability of the optimizer to use indexes。 Add an index on the objective column so that is can be used in both the WHERE and GROUP BY operations。 Drop the run_2 index because it has caused a conflict in the choice of key for this query。 Execute the run_2 index because it has caused a conflict in the choice of key for this query。 Add a composite index on (run,objective,stage) to allow the query to fully utilize an index。
明代李时珍所著（）是世界闻名的药物学巨著，共收载药物（）种，现已译成（）种文本。
起重机钢丝绳用卡子连接时，根据钢丝绳直径不同，使用不同数量的卡子，但最小不得少于（）。 2个。 3个。 4个。
发电机失磁后，机组转速（）。 升高。 降低。 不变。
Given： What is the result？（） Compilation fails.。 aAaA aAa AAaa AaA。 AAaa AaA aAa aAaA。 AaA AAaa aAaA aAa。 aAa AaA aAaA AAaa。
条形基础根据基础深度宜分段分层连续浇筑混凝土，一般不留（）。
