Sql Excution Plan Shows Different result for same inputs

Question

declare @name varchar(156)
set @name ='sara'
--Query 1:
SELECT [PNAME]  FROM [tbltest] where  [PNAME]  like '%'+@name+'%'

--Query 2:
SELECT [PNAME]  FROM [tbltest] where  [PNAME]  like '%sara%'

suppose that there is a NoneClustered Index on [PNAME] column of [tbltest]. when running Queries, Excution plan show index Seek For Query 1 and Index Scan for Query 2. i expected that Excution Paln Show Index Scan For both queries,but because of using parameter in the first Query,it Show Index Seek. So what i the mater? in both query we used '%' at oth side,and know that in this state ,sql does not consider index but why in first Query Excution Plan Show Index Seek? thanks

Answer 1

Query one uses a parameter, query 2 a constant.

The plan for query 2 will not be reused if you change the constant value.

The query for plan 1 can be. In this case, SQL Server (simply) leaves it's options open for reusing the plan.

AKA: the queries are not the same.

If you force parameterisation, then you should make both queries run like query 1. But I haven't tried...