SQL查询每天开始缓慢

Question

I have a basic query below.

Select [ID] 
FROM MyTable 
Where [TextBlobField] like '%test%'

This query takes a long time when I first run it each day. After that it only takes about 5 seconds. Next morning back to long query time. Is this because SQL is caching a index temporary?

How can I make this fast all the time? NOTE: I do not have permission to create my own index on the table. I can create a Stored Procedure, but don't know if that help? Should I create a view?

Answer 1

it is highly unlikely that the reason is an index cache. The reason: your query cannot make use of an index for the where clause. Although like can use an index, it cannot when the pattern starts with a wildcard.

However, you are on the right track. The reason is probably because the table itself needs to be read and cached in memory.

Although like doesn't use an index, you might be able to modify the query to use contains , taking advantage of full text indexing. You can learn more about this here .

Answer 2

That's usually because of caching.

One solution is to call that query once every morning automatically before your system is used by end users - that triggers the caching.