SQL 查询性能慢 'LIKE CNTR%04052021%

Question

we have a database that is growing every day. roughly 40M records as of today.

This table/database is located in Azure.

The table has a primary key 'ClassifierID', and the query is running on this primary key.

The primary key is in the format of ID + timestamp (mmddyyy HHMMSS), for example 'CNTR00220200 04052021 073000'

Here is the query to get all the IDs by date

 **Select distinct ScanID
 From ClassifierResults
 Where ClassifierID LIKE 'CNTR%04052020%**

Very simple and straightforward, but it sometimes takes over a min to complete. Do you have any suggestion how we can optimize the query? Thanks much.

Answer 1

The best thing here would be to fix your design so that a) you are not storing the ID and timestamp in the same text field, and b) you are storing the timestamp in a proper date/timestamp column. Using your single point of data, I would suggest the following table design:

ID           | timestamp
CNTR00220200 | timestamp '2021-04-05 07:30:00'

Then, create an index on (ID, timestamp) , and use this query:

SELECT *
FROM yourTable
WHERE ID LIKE 'CNTR%' AND
      timestamp >= '2021-04-05' AND timestamp < '2021-04-06';

The above query searches for records having an ID starting with CNTR and falling exactly on the date 2021-04-05 . Your SQL database should be able to use the composite index I suggested above on this query.