anxious! !! !! Very strange, please give me some advice about the speed of retrieving data ...

millgold

There is such a table in the database: A (a total of 40 fields, all fields are varchar type, more than 9,000 data)

TheID Date Number Heavy TheGoods ...
HH00001 2016-01-01 10 1000 Wood ......
HH00002 2016-05-01 50 6000 Steel ...

...
HH01111 2017-01-01 30 800 cloth ...
...

I used Sql statements to query the data, and a strange situation occurred:
select * from A where Date between '2016-01-01' and '2016-11-01'

If the date in the above statement should be 2017, then the data query becomes very slow (the data is about one hundred). "Other cases" speed is normal!

What is the cause of this? Is there any way to fix it? Please give pointers ...

Learn, pay attention to ...

dream88

Is it possible that many people are accessing the server?

cv4bf5d65fd

Index by Date column to see how fast~

hiqwolfzzh

Remove * and change to the corresponding column name
Although troublesome, the efficiency will be higher

millgold

Description of the landlord:
1. No more than 10 people access the server

2. I removed * and used only a few column names. After trying it, the effect is basically the same!

3. Index the Date column? The little brother is a rookie, this will not, can you teach me? ?

wgfxman

1. If the query often uses Date, you can consider building an index
2. Update table statistics

wgfxman

CREATE INDEX IdDate ON A(date);

UPDATE STATISTICS A

millgold

Description of the landlord:

CREATE INDEX IdDate ON A(date);

UPDATE STATISTICS A

Where should these sentences be written? ? ? ?