>>To date, my experience with SQL Server,
>>tells me that if the relationship SIZERAM / SIZEDB is very small 1
>>it is common to have performance degradation.
>>Certainly the size of RAM it must be larger than the size of the Client table including the indexes.
>
>The size of that table is 40 GB.
>
>I have requested more RAM since a very long time.
>
>>Another issues it is a bad optimization of @variables.
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>Are you saying that protection for SQL injection should be removed from all the commands? Parameterized approach has always been the case since a very long time. Or, is it that you are suggesting to avoid the SQL injection approach ONLY when using the full text index and use a direct approach instead?
>
>IAC, I checked the execution plan on the direct approach and I have attached the file.
>
>SQL Server seems to have offloaded the request to current index and only needs 1% from the full text index.
>
>How can we explain that?

No, you do need to use parameterized approach. However, you may be running in parameters sniffing problem. If that's the case, addition OPTION (RECOMPILE) to the end of the query may fix the problem.