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; <img src="https://nimg.ppkao.com/2018-08/tangxueping/2018080116105872201.jpg?sign=935d2e87bc06929dcaea9339b8f73ca2&t=62d08896" /> The iteminformation table has the following indexes; Mysql＞ SHOW INDEXES FROM iteminformation: <img src="https://nimg.ppkao.com/2018-08/tangxueping/2018080116111090166.jpg?sign=01dd2c6977a21dac6046aade71a4d6c6&t=62d08896" /> 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?（）..

第1题

[单选题] What is true regarding subqueries?（）

A、The inner query always sorts the results of the outer query. B、The outer query always sorts the results of the inner query. C、The outer query must return a value to the inner query. D、The inner query returns a value to the outer query. E、The inner query must always return a value or the outer query will give an error.

点击查看答案

第2题

[单选题] What is true regarding subqueries?（）

A、The inner query always sorts the results of the outer query B、The outer query always sorts the results of the inner query C、The outer query must return a value to the outer query D、The inner query returns a value to the outer query E、The inner query must always return a value or the outer query will give an error

点击查看答案

第3题

[] What is true regarding subqueries?（）

A、A. The inner query always sorts the results of the outer query B、B. The outer query always sorts the results of the inner query C、C. The outer query must return a value to the outer query D、D. The inner query returns a value to the outer query E、E. The inner query must always return a value or the outer query will give an error

点击查看答案

第4题

[多选题] A general purpose MySQL instance is configured with the following options: —log-slow-queries —long-query-time=,0001 —log-slow-admin-queries —general-log —log-bin —binlog-format=STATEMENT —innodb-flush-log-at-trx-commit=1 Which three statements are true（）。

A、The General Query Log records more data than the Binary Log B、The binary Log records more data than the General Query Log C、The Slow Query Log records more data than the General Query Log D、The General Query Log records more data than the Slow Query Log E、The Slow Query Log records more data than the Binary Log F、The Binary Log records more data than the Slow Query Log

点击查看答案

第5题

[单选题] A database exists as a read-intensive server that is operating with query_cachek_type =DEMAND. The database is refreshed periodically, but the resultset size of the queries does not fluctuate. Note the following details about this environment: A web application uses a limited set of queries. The Query Cache hit rate is high. All resultsets fit into the Query Cache. All queries are configured to use the Query Cache successfully. The response times for queries have recently started to increase. The cause for this has correctly been identified as the increase in the number of concurrent users accessing the web service. Based solely on the information provided, what is the most likely cause for this slowdown at the database level?（）

A、The Query Cache is pruning queries due to an increased number of requests B、Query_cache_min_res_unit has been exceeded, leading to an increased performance overhead due to additional memory block lookups C、Mutex contention on the Query Cache is forcing the queries to take longer due to its singlethreaded nature D、The average resultset of a query is increasing due to an increase in the number of users requiring SQL statement execution

点击查看答案

第6题

[单选题] You define a multiple-row subquery in the WHERE clause of an SQL query with a comparison operator "=".What happens when the main query is executed?（）

A、The main query executes with the first value returned by the subquery. B、The main query executes with the last value returned by the subquery. C、The main query executes with all the values returned by the subquery. D、The main query fails because the multiple-row subquery cannot be used with the comparison operator. E、You cannot define a multiple-row subquery in the WHERE clause of a SQL query.

点击查看答案

第7题

[单选题] You define a multiple-row subquery in the WHERE clause of an SQL query with a comparison operator "=".What happens when the main query is executed?（）

A、The main query executes with the first value returned by the subquery. B、The main query executes with the last value returned by the subquery. C、The main query executes with all the values returned by the subquery. D、The main query fails because the multiple-row subquery cannot be used with the comparison operator. E、You cannot define a multiple-row subquery in the WHERE clause of a SQL query.

点击查看答案

第8题

[单选题] You define a multiple-row subquery in the WHERE clause of an SQL query with a comparison operator "=". What happens when the main query is executed? （）

A、The main query executes with the first value returned by the subquery. B、The main query executes with the last value returned by the subquery. C、The main query executes with all the values returned by the subquery. D、The main query fails because the multiple-row subquery cannot be used with the comparison operator. E、You cannot define a multiple-row subquery in the WHERE clause of a SQL query.

点击查看答案

第9题

[单选题] EXHIBIT, Emp Table Exhibit A Exhibit B Examine the data from the EMP table. Evaluate this SQL statement: SELECT * FROM emp WHERE emp _ id = 3); WHERE commission = (SELECT commission FROM emp What is the result when the query is executed?（）

A、Exhibit A B、Exhibit B C、The query returns no rows D、The query fails because the outer query is retrieving more than one column E、The query fails because both the inner and outer queries are retrieving data from the same table.

点击查看答案

请使用微信扫码支付