The amount of time consumed by SQL queries

select * from log a,(select ,max(date) from logwhere id='10000'

group by

bwhere

Why is the following one time-consuming?

select * from log a,(select ,max(date) from loggroup by

bwhere and '10000'

1. Create a Junit test.

2. Use the setup() and teardown() methods.

3. Generate a session in two methods respectively, open a transaction, commit a transaction and close a session First test the local SQL query, that is, the commonly used SQL statement executes SQL through the createsqlquery method of the session, and loads the object to be queried.

4. The method of conditional query, Hibernate uses the method of :stuname to occupy the parameters in the SQL and passes"The name of the parameter","parameters") to assign a value.

5. The corresponding query result.

This can be done with the group by statement.

For example, the test table contains the following data:

To find out the sum of CNTs for each hour of the day on February 25, you can use the following statement:

with t as

select number rn from master..spt_values where type='p' and number<=23)

select hours,sum(isnull(cnt,0)) quantity from t left join test on ,begin date,12,2)

as int) group by

Query Result:

Use the job scheduled task execution statement to define the execution interval to 1 hour, and the query condition is that the year, month, and day are equal to the system time at that time.

The hour of the field is equal to the current hour hour(field)=hour(getdate()).